Psychometric properties of the Norwegian version of the Patient Generated Index in patients with rheumatic diseases participating in rehabilitation or self-management programmes

Objective. In rehabilitation, treatment is individually tailored to each patient's goals. Individualized instruments allow patients to choose domains that they consider important, which may make them particularly appropriate as evaluative tools in this setting. We aimed to evaluate the psychometric properties of the Norwegian version of the Patient Generated Index (PGI) in patients with rheumatic diseases participating in inpatient rehabilitation or self-management programmes. Methods. Patients completed the PGI together with other outcome measures at arrival and 5 and 52 weeks after arrival. The PGI was assessed for data quality by completion rates, reliability by the intraclass correlation coefficient (ICC), agreement by standard error of measurement (SEM) and smallest detectable change (SDC). Construct validity was assessed by testing a priori hypotheses regarding correlation between PGI scores and other outcome measures. Responsiveness was assessed by an a priori hypothesis regarding the correlation of different change scores and standardized response means (SRMs). Results. A total of 145 patients participated and 118 (81%) completed the PGI correctly. The ICC was 0.87, SEM 7.25 and SDC 20.10. Ninety-three per cent of the hypotheses of correlation were confirmed in tests for construct validity. Responsiveness was confirmed in 53% and 71% of hypotheses tested at 5 and 52 weeks. SRMs were 0.2 and 0.4, respectively. Conclusion. The results support the validity, reliability and responsiveness of the Norwegian version of the PGI in patients with rheumatic diseases and its application as an outcome measure in rehabilitation or self-management programmes. Further research is needed to improve completion rates for the PGI.