Objectives To compare two measures of systemic lupus erythematosus (SLE) response: the British Isles Lupus Assessment Group (BILAG)-based Composite Lupus Assessment (BICLA) and the Systemic Lupus Responder Index (SRI) against a clinician's assessment of improvement.

Methods Ninety-one lupus patients were identified with two visits at which Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) and BILAG had been scored and with active disease (SLEDAI≥6) at the first visit. A physician rated the disease activity at the second visit as clinically significant improvement, no change or worsening. SRI and BICLA were scored both with and without the medication criteria often used in trials to restrict response definitions.

Results 68 patients were considered improved, 17 same and 6 worse at follow-up. SRI versus BICLA, performed without considering medication changes, captured physician-rated improvement with 85% vs 76% sensitivity and 74% vs 78% specificity. With medication limits both instruments had 37% sensitivity and 96% specificity for physician-assessed improvement. Seven patients considered improved by the clinician met the BICLA but not the SRI definition of improvement by failing to achieve a four-point improvement in SLEDAI. 13 clinician-rated responders met SRI but not BICLA by improving in less than all organs.

Conclusions Shortfalls of SRI and BICLA may be due to BICLA only requiring partial improvement but in all organs versus SRI requiring full improvement in some manifestation(s) and not all organs. SRI and BICLA with medication restrictions are less likely to denote response when the physician disagrees and could provide stringent proof of efficacy in appropriately powered clinical trials.