Measuring social function in diverse cancer populations: Evaluation of measurement equivalence of the Patient...

Conceptual and psychometric measurement equivalence of self-report questionnaires are basic requirements for valid cross-cultural and demographic subgroup comparisons. The purpose of this study was to evaluate the psychometric measurement equivalence of a 10-item PROMIS^® Social Function short form in a diverse population-based sample of cancer patients obtained through the Measuring Your Health (MY-Health) study (n = 5,301). Participants were cancer survivors within six to 13 months of a diagnosis of one of seven cancer types, and spoke English, Spanish, or Mandarin Chinese. They completed a survey on sociodemographic and clinical characteristics, and health status. Psychometric measurement equivalence was evaluated with an item response theory approach to differential item functioning (DIF) detection and impact. Although an expert panel proposed that many of the 10 items might exhibit measurement bias, or DIF, based on gender, age, race/ethnicity, and/or education, no DIF was detected using the study's standard DIF criterion, and only one item in one sample comparison was flagged for DIF using a sensitivity DIF criterion. This item's flagged DIF had only a trivial impact on estimation of scores. Social function measures are especially important in cancer because the disease and its treatment can affect the quality of marital relationships, parental responsibilities, work abilities, and social activities. Having culturally relevant, linguistically equivalent and psychometrically sound patient-reported measures in multiple languages helps to overcome some common barriers to including underrepresented groups in research and to conducting cross-cultural research.