Assessing validity and reliability of the Positive Health and Individual Recovery Outcomes Counter questionnaires for measuring self-reported changes in positive health

Positive Health is gaining attention for measurement purposes. In this study, the 17-items Positive Health (PH17) questionnaire and the 12-items Individual Recovery Outcomes Counter (I.ROC12) questionnaire were investigated on usefulness for measuring self-reported changes in Positive Health. An observational study was performed in a Dutch post-covid-19 patient population to assess test-retest reliability (intraclass correlation coefficient (ICC), standard error of measurement (SEM), and smallest detectable change (SDC)), internal consistency and construct validity by hypothesis testing. PH17, I.ROC12 and – for comparison – EQ5D-VAS were completed at six (T6) and twelve (T12) months after hospital discharge and again within 5 days after T12 (retest). For PH17, test-retest reliability was good for five factors and the total score (ICC >0.7, SEM <10%), but not for the factor Future perspective (ICC 0.56). Internal consistency was too high for three factors (Physical fitness, Contentment, and Mental functioning, Cronbach’s alpha >0.9 and too low for the factor Future perspective (<0.59). For I.ROC12, reliability (ICC >0.9, SEM <10%) and internal consistency (0.7-0.9) were better than for PH17. Hypothesised coherences between the PH17 and I.ROC12 were confirmed indicating they cover similar Positive Health aspects. Coherence with the EQ5D-VAS also exists, but not for I.ROC12 on the change score. Both PH17 and I.ROC12 are reliable for measuring population-level change; I.ROC12 can also measure changes among individuals. Based on internal consistency, the I.ROC12 might be a better alternative to the PH17. The instrument choice should depend on the setting and measurement purpose such as for populations or individuals.