Reliability and validity of PROMIS measures administered by telephone interview in a longitudinal localized prostate cancer study

Purpose To evaluate the reliability and validity of six PROMIS measures (anxiety, depression, fatigue, pain interference, physical function, and sleep disturbance) telephone-administered to a diverse, population-based cohort of localized prostate cancer patients. Methods Newly diagnosed men were enrolled in the North Carolina Prostate Cancer Comparative Effectiveness and Survivorship Study. PROMIS measures were telephone administered pre-treatment (baseline), and at 3-months and 12-months post-treatment initiation (N = 778). Reliability was evaluated using Cronbach's alpha. Dimensionality was examined with bifactor models and explained common variance (ECV). Ordinal logistic regression models were used to detect potential differential item functioning (DIF) for key demographic groups. Convergent and discriminant validity were assessed by correlations with the legacy instruments Memorial Anxiety Scale for Prostate Cancer and SF-12v2. Known-groups validity was examined by age, race/ethnicity, comorbidity, and treatment. Results Each PROMIS measure had high Cronbach's alpha values (0.86-0.96) and was sufficiently unidimensional. Floor effects were observed for anxiety, depression, and pain interference measures; ceiling effects were observed for physical function. No DIF was detected. Convergent validity was established with moderate to strong correlations between PROMIS and legacy measures (0.41-0.77) of similar constructs. Discriminant validity was demonstrated with weak correlations between measures of dissimilar domains (–0.20––0.31). PROMIS measures detected differences across age, race/ethnicity, and comorbidity groups; no differences were found by treatment. Conclusions This study provides support for the reliability and construct validity of six PROMIS measures in prostate cancer, as well as the utility of telephone administration for assessing HRQoL in low literacy and hard-to-reach populations.