Psychometric Properties of Patient Global Assessment in Psoriatic Arthritis: A Systematic Literature Review

Abstract

Objective: Patient global assessment (PtGA) is a patient-reported outcome (PRO) that reflects a patient's judgment of their health/disease activity (DA). The objective of this systematic literature review was to assess the psychometric properties of PtGA in psoriatic arthritis (PsA).

Methods: Research articles reporting the assessment of psychometric properties of PtGA in PsA, listed in PubMed and extracted according to the Outcome Measures in Rheumatology (OMERACT) Filter 2.1 and the Consensus-based Standards for the Selection of Health Measurement Instruments (COSMIN) terminology, were selected. Validity was assessed for comprehensiveness (content), correlation with other DA instruments (construct), and with quality of life measurements (criterion). A metaanalysis regarding construct validity was performed. Correlations between PtGA variations and other indices' variations (external responsiveness) and PtGA variations after treatment (internal responsiveness) were collected. Data on the formulation of PtGA and its discordance with physician global assessment (PGA) were also collected.

Methods: Of 60 articles analyzed (comprising 17,453 patients), 44 were observational studies and 16 were trials. PtGA was assessed through 27 different formulations. In all the retrieved studies, PtGA assessed DA, and in 3 studies, PtGA was assessed as a variable of global health status. The correlation between PtGA and PROs was strong (ρ > 0.50), whereas with other DA indices and PGA, it ranged from weak to moderate (ρ 0.20-0.50). Three studies described a positive discordance (PtGA > PGA). Responsiveness, assessed in 24 studies, showed a strong correlation with joint count index variations (ρ 0.51-0.52).

Conclusion: PtGA is a valid and responsive tool in PsA. Correlations were higher with PROs and weaker with DA composite indices and PGA. PGA was usually scored lower than PtGA. A standardized formulation of PtGA would be useful.

Keywords: health status; patient outcome assessment; psoriatic arthritis; psychometric.