MD Andreas Stang
email: andreas.stang@medizin.uni-halle.de

PhD Ray M Merrill

PhD Oliver Kuss

Nationwide Rates of Conversion from Laparoscopic or Vaginal Hysterectomy to Open Abdominal Hysterectomy in Germany

Keywords: Epidemiology, Germany, hospital data, hysterectomy, incidence, population-based

Nationwide rates of conversion from laparoscopic or vaginal hysterectomy to open abdominal hysterectomy in Germany

Figures 1

Introduction

Hysterectomy is the most frequently performed major surgical procedure in gynecology across many places in the world [START_REF] Lefebvre | SOGC clinical guidelines. Hysterectomy[END_REF]. Several studies have shown marked variations of hysterectomy rates across and within industrialized countries

(2-7) and over time (2;7-9). It has been shown that selected factors influence hysterectomy rates beyond the incidence of genital tract diseases such as availability of obstetricians and gynecologists, the number of hospital beds per capita, the type of health-care insurance available, the gender of the gynecologists, the social class of the patient (10;11), available information about the different treatment modalities among patients [START_REF] Domenighetti | Effect of information campaign by the mass media on hysterectomy rates[END_REF], and cultural norms related to fertility-sparing, less definitive procedures. The increasing prevalence of obesity has also contributed to an increased rate of abnormal uterine bleeding, which, in turn, may contribute to greater use of hysterectomy (13;14).

Hysterectomy surveillance provides an indication of female reproductive health and how women are being treated for problems of the reproductive system. Populationbased nationwide hysterectomy rates in Germany (population of 42 million women)

have not been estimated until the current study. Hysterectomies are not performed in ambulatory surgery centers in Germany. In 2004, Germany introduced the DRG (diagnosis related groups) system for reimbursement of inpatient hospital services.

All individual hospitalizations with individual diagnostic and therapeutic codes contribute to the nationwide DRG statistics that provide a useful data source for epidemiologic purposes as recent studies with these data have shown [START_REF] Stang | Inpatient management of patients with skin cancer in Germany: an analysis of the nationwide DRG-statistic 2005-2006[END_REF][START_REF] Stang | A novel approach to estimate the German-wide incidence of testicular cancer[END_REF][START_REF] Stang | Micrographic surgery of skin cancer in German hospitals 2005-2006[END_REF].

The purpose of this study is to quantify nationwide hysterectomy rates by indication groups and by type of surgical approach. Furthermore, we studied factors that might be associated with the rate of conversion from hysterectomies that were started as vaginal or laparoscopic hysterectomies to open abdominal hysterectomies. German hysterectomy rates will be compared with recent studies of other countries.

Material and Methods

Based on an amendment of the hospital financing system in Germany in 1999, the We identified hysterectomies by use of the OPS codes 5-682: subtotal hysterectomy, produce the same reimbursement if the diagnoses (primary and secondary diagnoses) are identical. For example, hysterectomy for leiomyoma of the uterusgiven no comorbidity-produces a single DRG code N21.Z regardless of surgical approach. This DRG code is the basis for reimbursement.

Statistical Methods

Crude and age-specific hysterectomy rates were calculated with the midyear populations of the years 2005 and 2006 as the denominator. In a sensitivity analysis, we corrected the denominator in the rate calculation for women who have already had a hysterectomy. In other words, the denominator was adjusted by removing the estimated prevalence of women who have already had a hysterectomy. The agespecific prevalence of hysterectomy in the general population was estimated from a recent regional survey in Bremen among women aged 45-74 years [START_REF]Frauengesundheitsbericht Bremen[END_REF]. As agespecific prevalence of hysterectomy revealed a S-shaped pattern in Bremen, Germany, as well as in a survey in Utah, USA [START_REF] Merrill | Comparison of two methods based on crosssectional data for correcting corpus uterine cancer incidence and probabilities[END_REF], we estimated age-specific probabilities of hysterectomy prevalence and extrapolated hysterectomy probabilities (outside the observed age range) from a logistic regression model. Based on this model, we found an upper limit of hysterectomy prevalence in the population of 40.7% among women aged 85 years and more. This value minimized the Pearson goodness-of-fit statistic from an iterative search across a range (40%-60%) of upper limits of the hysterectomy prevalence among women aged 85 years or more.

Thereafter, we corrected the person-years at risk of the population and recalculated hysterectomy rates in Germany for all age groups. We estimated age-specific risks of conversion from laparoscopic or vaginal hysterectomy to open hysterectomy by linear risk models with disjoint indicator variables for the indication groups and age as a further covariate [START_REF] Greenland | Introduction to Regression Models[END_REF]. As the term "conversion risk" may be confused with adverse effects following conversion, we instead use the term "conversion rate" throughout the manuscript although the term "rate" is usually reserved for measures that include time in the denominator [START_REF] Rc | Definition of rates: some remarks on their use and misuse[END_REF]. Statistical analyses were performed using SAS 9.2 [START_REF]SAS for windows[END_REF].

Results

Overall, 3.6 per 1,000 women (any age) per year in Germany underwent hysterectomy. The corrected rate of hysterectomy that accounts for the hysterectomy prevalence was 4.3 per 1,000 women per year, reflecting a 19% increase. Hereafter, uncorrected rates for hysterectomy prevalence are reported. The highest hysterectomy rates were among women aged 40-49 years (9.9 per 1,000 women).

Mean and median age at hysterectomy were 52 years (standard deviation 13 years)

and 48 years (10% percentile 39 years, 90% percentile 72 years) respectively; and mean and median lengths of stay in the hospital were 9.8 days (standard deviation:

5.9 days) and 9 days (10% percentile: 5 days, 90% percentile: 15 days) respectively.

Twelve percent of all hysterectomies were associated with a primary malignant tumor of the genital organs and of these, primary malignant tumors of the uterus were the most frequent diagnosis (57%). Overall, 81% of all hysterectomies were associated with benign diseases of the genital tract. The ten most frequent primary diagnoses associated with hysterectomy for benign diseases of the genital tract accounted for 96% of all hysterectomies of this group. Leiomyoma of the uterus, genital prolapse, and excessive, frequent and irregular menstruation were the three most common primary diagnoses associated with hysterectomy accounting for 86% of all hysterectomies associated with benign diseases of the genital tract (Table 1).

As hysterectomies associated with benign diseases of the genital tract including benign cancers are often associated with more than one diagnosis, the relative frequencies of benign diseases of the genital tract are considerably higher if secondary diagnoses are also accounted for. For example, we observed overall However, an additional 53,816 hysterectomies were associated with a secondary diagnosis of N92. Only 0.16% of all hysterectomies associated with benign diseases of the genital tract had primary diagnoses that did not match any diagnosis of our pre-specified list of 24 frequent benign indications of hysterectomy.

Age-specific hysterectomy rates peaked at different ages depending on indication.

For example, highest hysterectomy rates for the treatment of genital tract cancers occurred among women aged 60-69 years whereas hysterectomy rates for the treatment of in-situ cancer and benign diseases of the genital tract were highest among women aged 40-49 years (Table 2).

The majority of hysterectomies were performed by the vaginal route (48.1%)

followed by abdominal open procedure (40.0%). Six percent of all hysterectomies were performed by LAVH and five percent were performed laparoscopically. 3). Whereas the conversion rate of laparoscopical hysterectomies monotoneously increased by age, this rate was about constant for vaginal hysterectomies (Figure 1).

The international comparison of population-wide hysterectomy rates among women aged 20 years or more related to benign diseases of the genital tract of the recent years shows that Sweden has the lowest hysterectomy rate and that the United

States and Australia have the highest rates. Germany has a rate between these extremes (Table 4).

Discussion

The German-wide hysterectomy rate was 3.6 per 1,000 women per year. Correcting the population used in the rate calculation for hysterectomy prevalence resulted in a 19% increase, a similar increase to that found in another study conducted in Australia [START_REF] Spilsbury | Persistent high rates of hysterectomy in Western Australia: a population-based study of 83 000 procedures over 23 years[END_REF]. As found in studies conducted in the United States (2;3), the highest hysterectomy rates were among women aged 40-49 years (9.9 per 1,000) with benign diseases of the genital tract as the most frequent indication group. As seen in other studies, uterine leiomyoma, genital prolapse, and excessive, frequent and irregular menstruation were the most frequent primary diagnoses for hysterectomy accounting for 86% of all hysterectomies in this indication group (2;3;8;9;13;22;28). The ACOG (American Congress of Obstetricians and Gynecologists) has suggested that concomitant bilateral oophorectomy should be considered during a hysterectomy for benign uterine diseases in peri-and postmenopausal women [START_REF] Camanni | Prophylactic bilateral oophorectomy during vaginal hysterectomy for benign pathology[END_REF].

In Germany, 4% and 26% of all hysterectomies for benign diseases of the genital tract included bilateral oophorectomy among women aged < 50 years and ≥ 50 years (most likely peri-and postmenopausal women) respectively. From 2000 through 2004, Whiteman et al. in the US observed that 37% of hysterectomies among women with benign diseases of the genital tract aged 15-44 years were accompanied by bilateral oophorectomy (2). This proportion was only 3% in Germany.

A few limitations to the study need mention. First, although we used a hierarchical algorithm similar to those that have been repeatedly used in other studies to group indications of hysterectomies [START_REF] Keshavarz | Hysterectomy surveillance -United States, 1994-1999[END_REF] (2) (36) [START_REF] Lepine | Hysterectomy surveillance -United States. 1980-1993[END_REF], this approach does not reflect the entire complexity of diagnoses for women undergoing hysterectomies [START_REF] Brett | Epidemiology of hysterectomy in the United States: demographic and reproductive factors in a nationally representative sample[END_REF]. Second, a more detailed stratification of hysterectomy rates for benign diseases of the uterus by single indications like uterine leiomyoma, prolaps etc. could not be reliably done based on DRG data and would necessitate a medical chart review that was impossible due to data protection laws in Germany. For the same reasons, we could not run detailed analysis of the causes of conversion (disease-related factors and clinician-related factors). Third, due to data confidentiality laws, German DRG data are completely anonymized and therefore validation studies of a random sample of these data is impossible.

In conclusion, this descriptive study provides unbiased nationwide hysterectomy rates for Germany and a benchmark for further studies. We provided a prevalenceadjusted hysterectomy rate. In addition, the rate of conversion of laparoscopical hysterectomies was considerably higher than the rate of vaginal hysterectomies. Age

  DRG reimbursement system became compulsory for hospitals in 2004. Hospitals annually transfer their individual hospitalization data to the Institute for the Hospital Renumeration System (InEK). After a plausibility control, the InEK forwards anonymized data to the Federal Bureau of Statistics. Since 2005, the Federal Bureau of Statistics provides individual hospitalization data for scientific uses. Hospitalizations are anonymized, which means that patients that are hospitalized more than once during the study period cannot be re-identified. We were able to use the hospitalization years 2005 and 2006 including overall 17.4 million hospitalizations among women.For each hospitalization, one primary diagnosis and up to 89 secondary diagnoses coded by ICD-10 can be documented. The diagnosis that led to the hospitalization assessed at the end of the hospitalization (i.e., when pathology and radiology reports were available) is defined as the primary one. In 2005, diagnoses were coded according to the ICD-10-GM (German Modification) version 2005[START_REF]ICD-10-GM 2005 Systematisches Verzeichnis: Internationale statistische Klassifikation der Krankheiten und verwandter Gesundheitsprobleme[END_REF]. In 2006, the ICD-10-GM version 2006 was used[START_REF]ICD-10-GM 2006 Systematisches Verzeichnis: Internationale statistische Klassifikation der Krankheiten und verwandter Gesundheitsprobleme[END_REF]. Up to 100 medical procedures can be coded according to a national classification of operations and procedures (OPS). In 2005 and 2006, the OPS versions of the years 2005 and 2006 respectively were used (20;21). For each hospital stay, the number of in-hospital days was recorded. The few differences between the ICD-10-GM and OPS versions of the years 2005 and 2006 were not relevant for our study question.

  The vaginal route of hysterectomy is considered as a first choice of all benign indications as the post-operative rates of morbidity and complications are lower than abdominal open hysterectomies according to the Society of Obstetricians and Gynaecologists of Canada (SOGC) clinical guidelines[START_REF] Lefebvre | SOGC clinical guidelines. Hysterectomy[END_REF]. We observed that 55% of all hysterectomies for benign indications were vaginal hysterectomies. In contrast, only 29% of hysterectomies for benign indications were vaginal hysterectomies in Sweden from 2001 through 2003[START_REF] Lundholm | Hysterectomy on benign indications in Sweden 1987-2003: a nationwide trend analysis[END_REF]. However, since 1993 the percentage of vaginal hysterectomies for benign indications steadily increased in Sweden and most recent unpublished percentages may be higher than those from 2001 through 2003. In the U.S., about 25% of hysterectomies for benign indications were vaginal hysterectomies[START_REF] Julian | Vaginal hysterectomy: an apparent exception to evidence-based decision making[END_REF].To the best of our knowledge, these are the first population-based, unbiased nationwide rate estimates of the conversion from laparoscopic or vaginal hysterectomy to open abdominal hysterectomy in Germany. For both types of hysterectomies, the rates of conversion were highest for indications including primary malignant genital tract cancer, other cancers as primary diagnosis, and neoplasia of uncertain behavior. The crude rates of conversion from laparoscopic and vaginal hysterectomy to open abdominal hysterectomy among benign indications were 10.5% and 1.1%. In contrast to studies that report conversion rates in highly selected patient series usually treated at a few centers, we provide nationwide, population-based conversion rates which complicates the comparison of our results with those reports.Published conversion rates vary considerably and may depend on several factors including patient-related factors like uterine size, pelvic and bowel adhesions, and body mass index, physician-related factors like the surgeons' experience, iatrogenic injuries (for example bleeding, perforation, uterovaginal fistula), and extent of surgery (adnexectomy, pelvic/aortic lymph node dissection)[START_REF] Leonard | Total laparoscopic hysterectomy: preoperative risk factors for conversion to laparotomy[END_REF][START_REF] Ng | Retrospective study of the success rates and complications associated with total laparoscopic hysterectomy[END_REF][START_REF] Tohic | Hysterectomy for benign uterine pathology among women without previous vaginal delivery[END_REF][START_REF] Eisenkop | Total laparoscopic hysterectomy with pelvic/aortic lymph node dissection for endometrial cancer--a consecutive series without case selection and comparison to laparotomy[END_REF][START_REF] Tunitsky | Does surgical volume influence short-term outcomes of laparoscopic hysterectomy?[END_REF]. The age-associated risk patterns of conversion differed by type of hysterectomy. For example, women aged 50 years who underwent hysterectomy for benign diseases of the genital tract had an estimated conversion risk of 11% and 1.1% for laparoscopic and vaginal hysterectomy respectively. In contrast, women aged 80 years who underwent hysterectomy for benign diseases of the genital tract had an estimated conversion risk of 22% and 0.5% for laparoscopic and vaginal hysterectomy respectively. Given the many factors that influence the decision to convert to open abdominal hysterectomy we cannot provide an explanation of the different age-associated risk patterns as clinical details beyond ICD-10 codes and procedure codes are missing in the DRG data set.

(

  laparoscopical hysterectomies only) and indication group (laparoscopical and vaginal hysterectomies) were associated with the rate of conversion to open abdominal hysterectomy.

  132,514 hysterectomies associated with leiomyoma of the uterus as the primary diagnosis. However, an additional 25,316 hysterectomies with a secondary diagnosis of leiomyoma of the uterus were observed. Similarly, 57,260 hysterectomies were

	associated with genital prolapse as the primary diagnosis and an additional 11,430
	hysterectomies had a secondary diagnosis of genital prolapse. The primary
	diagnosis "excessive, frequent & irregular menstruation (ICD-10: N92)" occurred only
	among 23,537 hysterectomies associated with benign diseases of the genital tract.

Table 1 Hysterectomy Indication Groups derived from a Hierarchical Algorithm and Diagnoses associated with 305.015 Hysterectomies in Germany from 2005 to 2006

 1

	Indication Groups and ICD-10 Codes	N	%	Bilateral
				Ooph. %
	Primary or secondary diagnosis: Primary	37,037	12.1	86.9
	malignant cancer of the female genital
	organs 1
	Cervix uteri (C53)	6,862
	Uterus (C54-C55)	20,982
	Ovary (C56)	9,838
	Other & unspecified female genital organs	709
	(C57)
	Placenta (C58)	13
	Primary or secondary diagnosis: Endometrial	5,063	1.7	40.3
	adenomatous hyperplasia (N85.1)
	Primary or secondary diagnosis: In-situ	6,337	2.1	14.3
	neoplasm of the genital organs 1
	Cervix uteri (D06)	6,145
	Other & unspecified part of the uterus	125
	(D07.0)
	Other & unspecified female genital organs	84
	(D07.3)

Primary or secondary diagnosis: Neoplasm of uncertain or unknown behaviour of female genital organs (D39) 5,646 1.9 55.2 Primary diagnosis: Primary malignant cancer other than C53-C58 as the primary diagnosis

	2,712 1,256 117 161 393 230 N 248,220 132,514 57,260 23,537 10,041 3,957 3,449 2,628 2,151 2,038 1,550 9,095 1.) the sum of diagnosis-specific indications does not necessarily add up to the 0.9 Colorectal cancer (C18-C21) Malignant neoplasm of retroperitoneum & peritoneum (C48) Malignant neoplasm of breast (C50) Malignant neoplasm of bladder (C67) Secondary malignant neoplasm of ovary (C79.6) Indication Groups and ICD-10 Codes % Bilateral 72.1 Ooph. % Benign diseases of the genital tract 2 81.4 12.4 Leiomyoma of the uterus (D25) Genital prolaps (N81) Excessive, frequent & irregular menstruation (N92) Endometriosis (N80) Benign neoplasm of ovary (D27) Other noninflammatory disorders of uterus, except cervix (N85) excluding endometrial adenomatous hyperplasia (N85.1) Dysplasia of cervix uteri (N87) Pain and other conditions associated with genital organs and menstrual cycle (N94) Other disorders of urinary system (N39) 3 Menopausal and other perimenopausal disorders (N95) Other diagnoses Legend Table 1 group total as more than one diagnosis of the group may have been the reason for hysterectomy 2.) Ten most frequent primary diagnosis associated with hysterectomy sorted in descending order (these 10 diagnoses include 96% of all hysterectomies associated with benign diseases) Other primary cancers (Table 1 continued) 3.) 1,937 out of 2,038 N39 codes (95%) were N39.3 (stress incontinence)

Table 2 Age-specific and Overall Hysterectomy Rates (per 100,000) in Germany of the Years 2005-2006

 2

	Indication-specific Age-specific Hysterectomy Rates

Legend Table

2

: SE: standard error of the rate.

Table 3 Crude and Age-adjusted Rates (%) (Conversion per 100 operations) and 95% Confidence Intervals of Conversion from Laparoscopical or Vaginal Hysterectomy to Open Abdominal Hysterectomy by Age in Germany of the Years 2005-2006

 3 Estimated rates are based on linear risk models[START_REF] Greenland | Introduction to Regression Models[END_REF]. Conversion from laparoscopic to open abdominal hysterectomy: 1,707 out of 16,674 hysterectomies (10.1%); conversion from vaginal to open abdominal hysterectomy: 1,616 out of 146,244 hysterectomies (1.1%);

	Hysterectomies (N)	Mean Age	Conversions	Crude Conversion Rate	Age-adj.
		(SD)	(N)		Conversion Rate

Table 4 A Comparison of Hysterectomy Rates per 1,000 Women Across Countries

 4

	Publication	Population	Calendar	Correction of	Age		Indication for Hysterectomy
			Period	Population 1	(Years)
						Any Cancer Precancerous	Benign
								lesions	diseases
	Merrill 2008 (3) 2)	United States	2001-2005	no	18+	5.5	0.4	0.2	4.9
	Spilsbury et al. 2006	Western	2003	no	20+	n.a.	n.a.	n.a.	5.4
	(7) 3)	Australia
	Lundholm et al., 2009	Sweden	2001-2003	no	18+	n.a.	n.a.	n.a.	2.1
	(9)
	This study 4)
		Germany	2005-2006	no	20+	4.5	0.5	0.2	3.6
		Germany	2005-2006	yes	20+	5.4	0.7	0.2	4.4

Table 4 1

 4 ) correction of population at risk for the prevalence of hysterectomy; 2) Cancer of the female genital organs (ICD-9: 179-184); precancerous lesions included endometrial cystic hyperplasia (ICD-9: 621.3) and carcinoma in situ of the genital organs (ICD-9: 233); 3) Spilsbury et al.[START_REF] Spilsbury | Persistent high rates of hysterectomy in Western Australia: a population-based study of 83 000 procedures over 23 years[END_REF] additionally reported the age-standardized (weights of the Australian population of 2001) additionally adjusted for the underlying prevalence of hysterectomy: 4.8 per 1,000 women; 4) This study: precancerous lesions included endometrial adenomatous hyperplasia (ICD-10: N85.1) and in-situ carcinoma of the genital organs (ICD-10: D06, D07.0, D07.3); n.a.: not applicable or not reported;

Acknowledgements

We are very grateful for the many helpful comments by Katrina Spilsbury, CHIRI, Centre for Population Health Research, Curtin University of Technology, Perth, Western Australia, on an earlier draft of this manuscript. We thank Mareike Kunze, Institut für Medizinische Epidemiologie, Biometrie und Informatik, Universitätsklinikum Halle und Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, Halle (Saale)University of Halle, for the preparation of the figures.

Disclosure of funding

No funding.


Matthew ; Falagas
email: m.falagas@aibs.gr

George Theocharis

MD Evridiki K Vouloumanou

MD Spyridon G Barbas

MD Theodore Spiropoulos

Petros I Rafailidis

MSc Matthew E Falagas

MD, MSc, DSc Matthew E Falagas

Comparison of characteristics of outpatients with 1 2009 H1N1 pandemic and seasonal influenza 2 3

Keywords: influenza, oseltamivir, age distribution, diagnosis, primary care 53 54

Background

The latest influenza pandemic intensified the interest in this infection. 28

Objective We aimed to compare the characteristics of outpatients with seasonal and 29 pandemic influenza. 30 Methods We retrospectively reviewed data regarding outpatients that sought medical 31 advice from a network of physicians performing house-call visits at the area of Attica, 32

). 35

Results A total of 195 and 1317 patients had a direct influenza test during the seasonal 36 and pandemic influenza period, respectively; 50.7% and 32% of these patients had a 37 positive test result for influenza, respectively. Viral culture or polymerase chain reaction 38 (PCR) were not implemented. Patients found positive for influenza during the pandemic 39 period, compared to those evaluated during the seasonal period, were younger (mean 40 age ± SD: 33 ± 17.2 vs 38.2 ± 19.2, p=0.008), more likely to have no comorbidity 41 (62.9% vs 45.5%, p=0.002), had milder clinical manifestations, and were treated with 42 more antibiotics (38.3% vs 9.9%, p<0.001). However, patients found positive during the 43 seasonal period were treated with more antivirals (oseltamivir: 69.1% vs 85.7%, 44 p=0.006). No difference was observed regarding the need for immediate hospitalization. 45

These findings were, consistent in the complementary analysis involving patients tested 46 for influenza during the compared periods. 47 Conclusion Despite the methodological limitations, our findings suggest that patients 48 with pandemic influenza were younger, had milder clinical manifestations, and were 49 less likely to have any kind of comorbidity, compared to patients with seasonal 50 influenza. 51 52

The recent influenza pandemic intensified the interest of health organizations, 66 physicians, media, and the public in this infection. Specifically, issues regarding the 67 epidemiological features, diagnosis and treatment of influenza underwent a re-68 evaluation under the perspective of the latest pandemic. 69 70 In particular, published reports have suggested that, younger age groups were 71 predominantly affected by the 2009 H1N1 pandemic influenza, [START_REF] Chowell | Severe respiratory disease 329 concurrent with the circulation of H1N1 influenza[END_REF][START_REF] Falagas | (H1N1) pandemic influenza: review of the Southern 332 hemisphere experience[END_REF][START_REF] Falagas | Epidemiological aspects of 2009 H1N1 influenza: the accumulating 335 experience from the Northern Hemisphere[END_REF] whereas, pregnant 72 and obese patients constituted a considerable percentage among more severely afflicted 73 2009 H1N1 pandemic influenza cases (including hospitalized and cases admitted in the 74 intensive care unit), as well as among fatalities. [START_REF] Falagas | (H1N1) pandemic influenza: review of the Southern 332 hemisphere experience[END_REF][START_REF] Falagas | Epidemiological aspects of 2009 H1N1 influenza: the accumulating 335 experience from the Northern Hemisphere[END_REF][START_REF] Plessa | Clinical 337 features, risk factors, and complications among pediatric patients with pandemic 338 influenza A (H1N1)[END_REF] With regard to influenza diagnosis, 75 published evidence suggests that the use of direct influenza tests during seasonal 76 influenza periods has been associated with reduced unnecessary antibiotic prescriptions, 77 hospitalizations and laboratory tests. [START_REF] Abanses | Impact of rapid influenza testing 340 at triage on management of febrile infants and young children[END_REF][START_REF] Bonner | Impact of the 343 rapid diagnosis of influenza on physician decision-making and patient management in 344 the pediatric emergency department: results of a randomized, prospective, controlled 345 trial[END_REF][START_REF] Theocharis | Evaluation of a direct test for seasonal influenza in outpatients[END_REF] However, the experience of their use during the 78 pandemic period was rather disappointing, as the sensitivities reported in studies 79 evaluating its application in various clinical settings were considered suboptimal. 8-10 80 The issue of influenza treatment was also re-evaluated during the pandemic period. 81 Many reports pointed out the benefit of early administration of antiviral treatment to 82 pandemic cases. [START_REF] Campanini | First case in Italy of acquired resistance 359 to oseltamivir in an immunocompromised patient with influenza A/H1N1v infection[END_REF][START_REF] Falagas | 362 Treatment options for 2009 H1N1 influenza: evaluation of the published evidence[END_REF][START_REF] Goldstein | Oseltamivir for treatment and 365 prevention of pandemic influenza A/H1N1 virus infection in households, Milwaukee, 366 2009[END_REF] However, reports on the emergence of pandemic viral strains 83 resistant to oseltamivir had also appeared in the literature. [START_REF] Tramontana | Oseltamivir resistance in adult 368 oncology and hematology patients infected with pandemic (H1N1) 2009 virus, 369 Australia[END_REF]

85

The aim of this study was to compare the epidemiological, clinical and treatment 86 characteristics of outpatients that sought medical advice from a network of physicians 87 performing house call visits in the area of Attica, Greece, and had a positive direct 88 influenza test, during the 2009 H1N1 pandemic period, as well as the preceding 89 seasonal (2008-2009) influenza period. Secondly, in a complementary analysis, we 90 aimed to compare the above-mentioned characteristics of all the patients that underwent 91 a direct influenza test in this specific clinical setting, at the respective influenza periods. 92

93

Methods

94

Patient population 95

We considered as eligible for inclusion patients that sought medical advice from a 96 network of physicians performing house-call visits at the area of Attica, Greece, who 97 underwent a direct influenza test either during the latest period of seasonal influenza 98 (http://www.corisbio.com). [START_REF]Influ A&B Uni-Strip Product Information[END_REF] The "Influ A&B Uni-Strip -Dry Swabs (C-1512)" test 110 consists of two sides sensitized with a monoclonal antibody specific for Influenza A and 111 B and thus allows detection of both influenza A and B, respectively. 112 113 A subset of the patients in the 1 st study period were included in a recent publication 114 focusing on the impact that the introduction of the direct influenza had on the decision 115 making, particularly the prescribing pattern, of the network of SOS Doctors. [START_REF] Theocharis | Evaluation of a direct test for seasonal influenza in outpatients[END_REF] 116 117

Data collection 118

We retrospectively reviewed the electronic databases of the SOS-Doctors network. We 119 retrieved data regarding the patient's demographic characteristics, types of comorbidity, 120 signs/symptoms that the patients complained for, types of diagnosis, treatment 121 prescribed, as well as the need for immediate hospitalization. 122 123

Data analysis 124

Our primary analysis referred to the comparison regarding the demographic 125 characteristics, types of comorbidity, symptoms, diagnosis, as well as the need for 126 immediate hospitalization were performed between the subgroups of the patients that 127 had a positive direct test for influenza during the evaluated influenza periods. In 128 addition, in a complementary analysis we compared the above-mentioned features for 129 the sub-groups of all the patients that were tested for influenza during the seasonal and 130 pandemic period, respectively. The chi square test was used for all the evaluated 131 dichotomous variables, whereas the Student's t-test or its non-parametric analogue, the 132 Mann-Whitney U test, were used when appropriate for all the evaluated continuous 133 variables. A p-value<0. 05 compared to those with a positive test during the seasonal period (13%). Moreover, 151 patients that did not have any type of comorbidity constituted a significantly higher 152 percentage among patients with a positive test during the pandemic (62%) period, 153 compared to those with a positive test during the seasonal period (45%). No difference 154 was observed in the comparisons regarding the other evaluated types of comorbidity 155 (detailed data are presented in Table 1). 156 157 Regarding the signs and symptoms for which the evaluated patients complained for, 158 febrile episodes, cough, rigor, nasal congestion/discharge, headache, and 159 myalgia/arthralgia were reported significantly more frequently from patients that were 160 found positive during the seasonal period, whereas the patients that were found positive 161 during the pandemic period complained significantly more frequently for sore throat. 162 No differences were observed in the remaining comparisons (Table1). 163 164 With regard to treatment characteristics, antivirals (oseltamivir), anticongestants, and 165 anti-asthmatic agents were prescribed significantly more frequently to patients found 166 positive during the seasonal period, whereas antibiotics were prescribed significantly 167 more frequently to patients that were found positive during the pandemic period. 168 Specific data regarding the remaining comparisons of treatment characteristics are 169 presented in Table 1. Finally, no difference was observed between the compared groups 170 regarding the need for immediate hospitalization. 171 172

Secondary analysis: (patients that underwent a direct influenza test during seasonal 173 vs pandemic influenza period) 174

A total of 195 and 1317 patients underwent a direct influenza test during the seasonal 175 and pandemic influenza period, respectively. No difference was found regarding sex 176 between the compared groups. Patients tested during the pandemic period were younger 177 compared to patients that were tested during the seasonal influenza period (mean age ± 178 SD: 41.1 ± 20.6 vs 36.7 ± 19.5, p=0.02). Moreover, pediatric patients were encountered 179 significantly more frequently in the pandemic (17%) versus the seasonal period (8%). 180 Detailed data regarding comorbidity were not available for a considerable percentage of 181 the evaluated patients. In this regard, we were precluded from comparing the types of 182 comorbidity between patients that were tested for influenza during the pandemic and the 183 preceding seasonal influenza period. 184 185 Febrile episodes, cough, rigor, nasal congestion/discharge, headache, and 186 myalgia/arthralgia were reported significantly more frequently from patients that were 187 tested during the seasonal influenza period compared to those tested during the 188 pandemic influenza period. On the other hand, patients tested during the pandemic 189 period complained for sore throat significantly more frequently compared to those 190 tested during the seasonal influenza period. No differences were observed regarding the 191 evaluated signs and symptoms between the compared groups (Table 2 that patients with pandemic influenza were younger compared to patients with seasonal 225 influenza. On the other hand, symptoms including cough, myalgias/arthralgias, and 226 pleuritic chest pain were more frequently encountered among patients with pandemic 227 versus seasonal influenza. [START_REF] Shiley | Differences in 376 the epidemiological characteristics and clinical outcomes of pandemic (H1N1) 2009 377 influenza, compared with seasonal influenza[END_REF] Yet, in our study, cough and myalgia were more common 228 among seasonal compared to pandemic cases. Another study also reported that 229 hospitalized patients with pandemic influenza were younger compared to hospitalized 230 patients with seasonal influenza. [START_REF] Chang | Comparison of 380 adult patients hospitalised with pandemic (H1N1) 2009 influenza and seasonal 381 influenza during the "PROTECT" phase of the pandemic response[END_REF] 231 232 In addition, with regard to patients' comorbidity, no difference was observed between 233 patients with seasonal and pandemic influenza, with the exception of pregnancy, [START_REF] Shiley | Differences in 376 the epidemiological characteristics and clinical outcomes of pandemic (H1N1) 2009 377 influenza, compared with seasonal influenza[END_REF] in the 234 first of the above-mentioned studies, whereas the other study noted that hospitalized 235 patients with pandemic influenza were less likely to be immunocompromised as 236 opposed to patients with seasonal influenza. [START_REF] Chang | Comparison of 380 adult patients hospitalised with pandemic (H1N1) 2009 influenza and seasonal 381 influenza during the "PROTECT" phase of the pandemic response[END_REF] In our study, otherwise healthy patients 237 were encountered more frequently among patients with a positive test result during the 238 period. This observation may reflect the high transmissibility rate of the 2009 H1N1 240 pandemic influenza virus. [START_REF] Paine | Transmissibility of 2009 pandemic 384 influenza A(H1N1) in New Zealand: effective reproduction number and influence of 385 age, ethnicity and importations[END_REF] Another possible explanation may be the fact that younger 241 patients were encountered more frequently among patients with a positive test for 242 pandemic influenza compared to seasonal. Young individuals are more likely to have 243 less comorbidity compared to elderly. Preliminary reports had also suggested that 244 patients with specific types of comorbidity (obese, morbidly obese, pregnant patients) 245 constituted considerable proportions of the confirmed influenza cases and more severely 246 afflicted influenza cases. 2, 3 Yet, we observed no differences regarding any of the 247 evaluated types of comorbidity between pandemic and seasonal influenza cases. The 248 retrospective methodology of our study may potentially account for this observation. 249 Specifically, comorbidity data may have been less likely to be recorded, as opposed to 250 data regarding clinical symptoms and treatment. 251 252 Based on the evaluation of the reported clinical signs and symptoms, the patients tested 253 and those with a positive direct test for influenza during the seasonal influenza period, 254 had more severe clinical manifestations compared to patients evaluated during the 255 pandemic period. Indeed, most of the pandemic influenza cases, apart from those with 256 considerable comorbidity that were considered to predispose for more severe disease 257 (including obesity and pregnancy), were cases of mild severity. [START_REF] Tang | Differing symptom patterns in early 387 pandemic vs seasonal influenza infections[END_REF][START_REF] Jeong | Mild form of 2009 H1N1 389 influenza infection detected by active surveillance: implications for infection control[END_REF][START_REF] Mclean | Pandemic (H1N1) 2009 influenza in 392 the UK: clinical and epidemiological findings from the first few hundred (FF100) cases[END_REF] On the contrary, 258 patients tested, as well as those with a positive test complained significantly more 259 frequently for sore throat compared to the respective evaluated patients during the 260 seasonal period. Published evidence suggests that sore throat was one of the symptoms 261 that differentiated the clinical manifestations of seasonal and pandemic influenza 262 infection. Specifically, a recently published large prospective study suggested that the 263 odds of patients that had sore throat to develop pandemic compared to seasonal 264 influenza were 1.4 times as high, relatively to when they didn't have these symptoms. [START_REF] Tang | Differing symptom patterns in early 387 pandemic vs seasonal influenza infections[END_REF] 265 266

In our complementary analysis, patients with a positive test constituted a significantly 267 higher percentage among patients tested during the seasonal versus the pandemic 268 influenza period. Many factors may possibly account for this specific observation. 269 Firstly, it should be mentioned that the performance of direct influenza test during the 270 recent influenza pandemic has been questioned. Specifically, the reported sensitivities 271 of such tests were considered as rather low. [START_REF] Ginocchio | Evaluation of multiple test methods for 350 the detection of the novel 2009 influenza A (H1N1) during the New York City 351 outbreak[END_REF][START_REF] Hawkes | Sensitivity of 353 rapid influenza diagnostic testing for swine-origin 2009 a (H1N1) influenza virus in 354 children[END_REF] According to the manufacturer's product 272 information, the sensitivity and specificity of the direct influenza test used in our 273 with real time-PCR), and the sensitivity and specificity for the detection of seasonal 276 influenza B were 97% and 100% (compared with time-resolved fluoroimmunoassay). [START_REF]Influ A&B Uni-Strip Product Information[END_REF] 277 However, the available published evidence regarding the diagnostic performance of this 278 specific direct test for pandemic influenza is conflicting. Specifically, the reported 279 specificity of this test is excellent (100%), whereas sensitivity is low (31.7%). [START_REF] Ciblak | 395 Sensitivity of rapid influenza antigen tests in the diagnosis of pandemic (H1N1)2009 396 compared with the standard rRT-PCR technique during the 2009 pandemic in Turkey. 397[END_REF]

281

With regard to treatment characteristics, significantly more antiviral agents were 282 prescribed to patients found positive for influenza during the seasonal compared to the 283 pandemic influenza period. Indeed, an evaluation of preliminary evidence regarding 284 treatment strategies used for cases of pandemic influenza suggested that a considerable 285 percentage of the evaluated patients (85.0%) received antibiotic treatment. [START_REF] Falagas | 362 Treatment options for 2009 H1N1 influenza: evaluation of the published evidence[END_REF] However, 286 one should consider the considerable proportion of missing treatment data during the 287 interpretation of the respective findings. Another speculation that may be attempted is 288 the fact that the potential of the emergence of a pandemic influenza strain resistant to 289 the contemporary commercially available antiviral agents may have possibly made 290 physicians reluctant to prescribe these drugs. Indeed, reports on the emergence of 291 pandemic strains resistant to oseltamivir had appeared in the literature during the 292 pandemic period. [START_REF]Oseltamivir-resistant 2009 pandemic influenza A (H1N1) virus infection in two 399 summer campers receiving prophylaxis--North Carolina, 2009[END_REF][START_REF] Chen | Oseltamivir-resistant influenza A pandemic 402 (H1N1) 2009 virus, Hong Kong, China[END_REF][START_REF] Gulland | First cases of spread of oseltamivir resistant swine flu between 404 patients are reported in Wales[END_REF] On the other hand, considering the alarmingly high rates of 293 antibiotic resistance reported for respiratory pathogens, [START_REF] Falagas | Tigecycline for the treatment of patients with 406 community-acquired pneumonia requiring hospitalization[END_REF][START_REF] Falagas | Inhaled colistin for the treatment of tracheobronchitis and pneumonia in critically 410 ill children without cystic fibrosis[END_REF][START_REF] Vardakas | Comparison of community-acquired 412 pneumonia due to methicillin-resistant and methicillin-susceptible Staphylococcus 413 aureus producing the Panton-Valentine leukocidin[END_REF] a more conservative 294 therapeutic approach with regard to antibiotic treatment to patients with evidence of 295 viral infections, including influenza, may eventually confer considerable benefit from an 296 individual-patient care, as well from a public health perspective. 297 298 Specific limitations must be taken into consideration before the extrapolation of the 299 findings of our study. Firstly, our findings refer to a specific clinical setting and to a 300 patient population with specific characteristics. Previously published experience has 301 suggested that patients older than 60 years old constitute a considerable percentage (up 302 to 50%) of the target patient population of this specific network of physicians. [START_REF] Peppas | An analysis of patient house 416 calls in the area of Attica, Greece[END_REF] 303 Selection bias may have also possibly influenced our findings, as the number of patients 304 in the pandemic group by far exceeds the number of the patients in the seasonal group. 305 However, this observation may be considered as expected, given the high demand of 306 relevant medical services during the pandemic period. The intrinsic limitations of a 307 retrospective study design may have also potentially influenced our findings. Finally, 308

F

( 1 /

 1 1/2009-1/5/2009), or during the period of 2009 H1N1 pandemic influenza 99 5/2009-15/4/2010). Since the 1 st confirmed case of 2009 H1N1 pandemic influenza 100 in Greece was reported at the 16 th of May 2009, we excluded the period 1/5/2009-101 15/5/2009 from our analysis. The direct test was performed at the discretion of the 102 physician performing the house-call visit. The diagnosis was also at the discretion of the 103 physician. Specifically, it was based on the patient's clinical manifestations, along with 104 epidemiological aspects (if any). Diagnostic methods including viral culture and/or PCR 105 were not implemented in our study. 106 107 The direct influenza test used during both the evaluated periods was the "Influ A&B 108 Uni-Strip -Dry Swabs (C-1512)" test, manufactured by Coris BioConcept 109

  observed between the compared groups regarding the need for 204 immediate hospitalization. 205 206 Discussion 207 According to our findings, patients with a positive direct test for influenza during the 208 2009 pandemic period were younger and had milder clinical manifestations (as inferred 209 by the signs and symptoms that the patients complained for) compared to those that had 210 a positive test during the seasonal influenza period. Otherwise healthy and pediatric 211 patients were represented by significantly higher percentages among patients found 212 positive for influenza during the pandemic versus the seasonal period. Regarding 213 treatment, antivirals, particularly oseltamivir, were prescribed significantly more 214 frequently to patients found positive for influenza during the seasonal period, whereas 215 antibiotics were prescribed significantly more frequently to patients found positive for 216 influenza during the seasonal period. The above findings were consistent in the 217 complementary analysis regarding the patients that underwent a direct influenza test 218 during the respective influenza periods. 219 220 Our findings regarding the age distribution of patients with pandemic and seasonal 221 influenza are in accordance with another recently published study that focused on the 222 comparison of the epidemiological characteristics of outpatients, as well as inpatients 223 with seasonal and 2009 H1N1 pandemic influenza. Specifically, this study suggested 224

  compared to those found positive during the seasonal influenza 239

  namely Influ A&B Uni-Strip -Dry Swabs (C-1512), for the detection of 274 seasonal influenza A were considerably high (77% and 100%, respectively, compared 275

Primary analysis: (patients with a positive direct influenza test result during seasonal 141 vs pandemic influenza period) 142

	135	Open Epi software was used to perform the comparisons regarding the outcomes
	136	expresses as dichotomous variables, 16 whereas the SPSS Software was used for the
	137	continuous variables.
	138
	139	Results
	140
	143 144 145 146	A total of 99 and 424 patients had a positive test for influenza during the seasonal and F pandemic influenza period respectively, constituting the 50.7% and 32% of the patients o tested for influenza during the respective evaluated influenza periods. No difference was r found regarding sex between the compared groups. Patients found positive during the
	147	P pandemic period were younger compared to patients that were found positive during the
	148	e seasonal influenza period [mean age ± standard deviation (SD): 38.2 ± 19.2 vs 33 ±
	149 150	17.2, p=0.008]. Additionally, pediatric patients constituted a significantly higher e r percentage among patients with a positive test during the pandemic (23%) period,
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	134	was considered as indicative of statistical significance. The
		6

Table 1 . Characteristics and outcomes of the patients with a positive direct test for influenza.

 1 based on the results of a direct influenza test, whereas no other 309 confirmatory methods like viral culture or polymerase chain reaction (PCR) were 310 available in this specific primary-care clinical setting. The rather low sensitivities and 311 specificities of rapid influenza tests used in various clinical settings during the latest 312 influenza pandemic should also be considered in the interpretation of the findings of our 313

	314	influenza diagnosis was study.
	315
	316	In conclusion, our findings suggest that patients with a positive direct test result during
	317	the pandemic influenza period were younger, had milder clinical manifestations, and
	318 319 320	were less likely to have any type of comorbidity compared to patients with a positive o test result during the evaluated seasonal influenza period. Despite the intrinsic r limitations of the retrospective study, our study provides useful comparative data
	321	P regarding the epidemiological, clinical, as well as treatment characteristics of a
	322	e considerable number of outpatients evaluated in a primary care setting during the latest
	323 324	pandemic influenza, as well as the preceding seasonal influenza period. e r
	325 326	Funding and Acknowledgements None	R
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			11

Table 2 . Characteristics and outcomes of the tested patients.

 2

		Patients tested	Patients tested during
		during the seasonal influenza period	the pandemic H1N1 influenza period	P value
		(N=195)	(N=1317)
	Demographic characteristics
	Sex [females]	91 (46.7)	640 (48.6)	0.67
	Age (Mean, ± SD, years)	41.1 ± 20.6	36.7 ± 19.5	0.02 ‡ ‡
	Pediatric patients	16 (8.2)	219 (16.6)	0.003
	(<18 years)
		n/N (%)
	Signs/symptoms
	Number of evaluated patients	182/195 (93.3)	1213/1317 (92.1)
	Febrile episode	180 (98.9)	1047 (86.3)	<0.001
	Sore throat	35 (19.2)	395 (32.6)	<0.001
	Cough	144 (79.1)	790 (65.1)	<0.001
	Rigor	24 (13.2)	76 (6.3)	0.001
	Nasal congestion/discharge	133 (73.1)	326 (26.9)	<0.001
	Headache	54 (29.7)	128 (10.6)	<0.001
	Otalgia	1 (0.5)	7 (0.6)	>0.999
	Asthmatic crisis	0	1 (0.08)	>0.999
	Fatigue/body aches	40 (22.0)	206 (17.0)	0.12
	Myalgia/arthralgia	101 (55.5)	310 (25.6)	<0.001
	Dyspnea/tachypnea	4 (2.2)	43 (3.5)	0.49
	Thoracic pain	1 (0.5)	6 (0.5)	>0.999
	Nausea/vomiting	16 (8.8)	77 (6.3)	0.28
	Diarrhea/abdominal pain	2 (1.1)	30 (2.5)	0.38
	Dizziness/loss of	1 (0.5)	11 (0.9)	>0.999
	consciousness
	Treatment
	Number of evaluated patients	164/195 (84.1)	839/1317 (63.7)
	Antivirals (oseltamivir)	80 (48.8)	240 (28.6)	<0.001
	Analgesics	29 (17.7)	107 (12.8)	0.12
	Anti-cough drugs	42 (25.6)	175 (20.9)	0.21
	Antibiotics	52 (31.7)	464 (55.3)	<0.001
	Anticongestants	32 (19.5)	69 (8.2)	<0.001
	Antihistamines	21 (12.8)	67 (8.0)	0.06
	NSAIDs	10 (6.1)	43 (5.1)	0.75
	Corticosteroids	2 (1.2)	2 (0.2)	0.25
	Corticosteroids + β2 agonist	7 (4.3)	42 (5.0)	0.84
	Anti-asthmatics	29 (17.7)	74 (8.8)	0.001
	Other *	28 (17.1)	93 (11.1)	0.043
	Hospitalization
	Number of evaluated patients	195/195 (100)	1317/1317 (100)
	Yes	4 (2.1)	19 (1.4)	0.39
	Abbreviations: SD: standard deviation, NR: not-reported, NA: non-applicable. 427
	‡ ‡: p value: Asymp. Sig. (2-tailed) for Mann-Whitney U test. 428
	*: Including: anti-emetics, gastroprotective agents, B-blockers, oral antiseptics, probiotics, antifungals 429
	430