Item Property	Reason for Change or Deletion
Clarity or relevance	• Reported as not relevant by a large segment of the target population • Generates an unacceptably large amount of missing data points • Generates many questions or requests for clarification from patients as they complete the PRO instrument • Patients interpret items and responses in a way that is inconsistent with the PRO instrument’s conceptual framework
Response range	• A high percent of patients respond at the floor (response scale’s worst end) or ceiling (response scale’s optimal end) • Patients note that none of the response choices applies to them • Distribution of item responses is highly skewed
Variability	• All patients give the same answer (i.e., no variance) • Most patients choose only one response choice • Differences among patients are not detected when important differences are known
Reproducibility	• Unstable scores over time when there is no logical reason for variation from one assessment to the next
Inter-item correlation	• Item highly correlated (redundant) withother items in the same concept of interest
Ability to detect change	• Item is not sensitive (i.e., does not change when there is a known change in the concepts of interest)
Item discrimination	• Item is highly correlated with measures of concepts other than the one it is intended to measure • Item does not show variability in relation to some known population characteristics (i.e., severity level, classification of condition, or other known characteristic)
Redundancy	• Item duplicates information collected with other items that have equal or better measurement properties
Recall period	• The population, disease state, or application of the instrument can affect the appropriateness of the recall period