Measurement Properties of Outcome Instruments for Large-Vessel Vasculitis: A Systematic Literature Review.

Objective. To systematically review the measurement properties of outcome instruments used in large-vessel Methods. MEDLINE, Embase, Cochrane, and Scopus databases were searched for studies published from inception to July 14, 2020, that addressed measurement properties of instruments used in giant cell arteritis (GCA) and Takayasu arteritis (TA). The measurement properties of the instruments identified were collected following the Outcome Measures in Rheumatology (OMERACT) and Consensus-Based Standards for the Selection of Health Measurement Instruments (COSMIN) frameworks. Instruments were grouped according to the following domains measured: disease activity/damage, organ function, and health-related quality of life (HRQOL)/health status. Results. From 3534 articles identified, 13 met the predefined criteria. These studies addressed 12 instruments: 4 specific to TA, 2 designed for all types of systemic vasculitis, and 6 non-disease-specific instruments. No instruments specific to GCA were identified. Regarding TA, the Indian Takayasu Clinical Activity Score (ITAS) showed very good consistency, adequate reliability, but doubtful validity for disease activity. The Disease Extent Index-Takayasu (DEI-Tak) showed adequate construct validity but doubtful discriminating validity for disease activity/damage. Instruments, including the Vasculitis Damage Index and the Birmingham Vasculitis Activity Score, were poorly assessed for disease activity/damage. In total, 6 non-vasculitis-specific patient-reported outcome (PRO) instruments showed inadequate validity in GCA/TA. Conclusion. The measurement properties of 12 outcome instruments for LVV covering the OMERACT domains of disease activity/damage, organ function, and HRQOL were assessed. The ITAS and the DEI-Tak were the instruments with the most adequate measurement properties for disease activity/damage in TA. Disease activity/damage instruments specific to GCA, as well as validated PROs for both GCA and TA, are lacking.