Objective: Patient Global Assessment (PtGA) is a patient-reported outcome (PRO) that reflects patients' judgment of 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, extracted according to the OMERACT Filter 2.1 and the COSMIN terminology, were selected. Validity was assessed for comprehensiveness (content), correlation with other DA instruments (construct) and with quality of life measurements (criterion). A meta-analysis 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 the PtGA and its discordance with physician global assessment (PhGA) were also collected.
Results: Of 60 articles analysed (17453 patients), 44 were observational studies and 16 were trials. PtGA was assessed through 27 different formulations. In all the retrieved studies PtGA assessed DA, in 3 global health status. The correlation between PtGA and PROs was strong (R>0.50), while with other DA indices and PhGA, it ranged from weak to moderate (R=0.20-0.50), and three studies described a positive discordance (PtGA > PhGA). Responsiveness, assessed in 24 studies, showed a strong correlation (R=0.51-0.52) with joint count index variations.
Conclusion: PtGA is a valid and responsive tool in PsA. Correlations were higher with PROs and weaker with DA composite indices and PhGA. PhGA was usually scored lower than PtGA. A standardized formulation of PtGA would be useful.