Use of the Patient-generated Index in systemic sclerosis to assess patient-centered outcomes

Objective. To evaluate the content and construct validity of an individualized patient-reported instrument, the Patient-generated Index (PGI), in patients with systemic sclerosis (SSc), and to compare its performance to that of other instruments and to the Patient-reported Outcomes Measurement Information System (PROMIS) framework. Methods. Patients identified the 5 most important life areas affected by SSc, which we categorized into domains of the PROMIS framework (mental, physical, and social). Correlations were obtained between PGI and the Health Assessment Questionnaire (HAQ), the Medical Outcomes Study Short Form-36 (SF-36), and the Symptom Burden Index (SBI) scores. Results. Sixty-two patients with SSc completed the PGI: 87% women, 69% white, mean age 53 years, mean disease duration 8 years, and 63% with diffuse disease. A total of 258 individual life area responses were recorded: 54% in social health (social function and relationship subcomponents); 28% in physical health (physical function, symptoms, general physical health); and 19% in mental health (consisting largely of the affect subcomponent). Patient PGI responses were categorized into 6 of the 7 subcomponents of the PROMIS framework; substance use/alcohol was not identified. Statistically significant correlations ranging in absolute value from 0.26 to 0.50 were observed between the PGI and the HAQ, SF-36 summary component scores, and the large majority of SF-36 subscales and SBI components. Conclusion. The PGI is a personalized instrument that adequately assessed a wide range of health-related quality of life outcomes within the PROMIS framework. The PGI captured additional constructs not yet defined within the framework that are important for patients with SSc.