Table 3 Common Reasons for Changing PRO Instruments During Initial Development
Item Property | Reason for Change or Deletion |
|---|---|
Clarity or relevance | • Reported as not relevant by a large segment of the population of interest • 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 conceptual framework |
Response range | • A high percent of patients respond at the floor (worst end of the response scale) or ceiling (optimal end of the response scale) • Patients note that none of the response choices apply to them • Item means are highly skewed |
Variability | • All patients give the same answer (i.e., no variance) • Most patients choose only one of the response choices • 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 uncorrelated with other items in the same concept of interest |
Ability to detect change | • Item is nonresponsive (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 |
Redundancy | • Item duplicates information collected with other items that have equal or better measurement properties |