Background/Purpose: Cell-Bound Complement Activation Products (CB-CAPs) in multianalyte assay panel (MAP) is a diagnostic immunology laboratory test with established clinical validity in distinguishing systemic lupus erythematosus (SLE) from other rheumatic diseases. The Clinical Laboratory Assessment and Recommendation (CARE) for Lupus study was designed to evaluate the clinical utility of this testing method in diagnosing SLE.

Methods: CARE for Lupus was a multicentered, randomized, and prospective study that enrolled patients evaluated for a suspicion of SLE by board certified rheumatologists (within three months of referral). At baseline, all patients presented with an history of antinuclear antibody positivity and were randomized (1:1) to standard diagnostic laboratory testing (SDLT, all ordered at the discretion of the rheumatologist) or to CB-CAPs/MAP testing, which reports a two-tiered index test result and has 80% sensitivity and 86% specificity for SLE. The primary end-point was based on the change in the physician likelihood of SLE on a 5-point Likert scale collected before and after testing (at 4 and 12-weeks). Changes in pharmacological treatment based on laboratory results were assessed in both arms. Statistical analysis consisted of Wilcoxon and Fisher’s Exact tests.

Results: A total of 145 subjects were enrolled at 32 sites and randomized to SDLT arm (n=73 subjects, mean [SEM] age=48±2 years, 94% females) and CB-CAPs/MAP arm (n=72 subjects, 50±2 years, 93% females). Positivity rate for CB-CAPs/MAP was similar in the 2 groups (15.1% in SDLT arm vs. 12.5% in CB-CAPs/MAP arm, p=0.65). At enrollment (pre-test), likelihood of SLE in SDLT and CB-CAPs/MAP arms was similar (Table). At the 4 weeks follow-up visit, patients randomized to the CB-CAPs/MAP testing arm presented with greater decrease in the likelihood of SLE than those randomized to the SDLT arm (p=0.027) and these differences remained significant at the 12-week follow-up visit (p=0.025) (Table). We observed a significantly greater decrease in the likelihood of SLE (decrease ≥1 point from enrollment) in the group of patients randomized to CB-CAPs/MAP testing arm (40/72, 56%) compared to the SDLT arm (27/73, 37%) (difference= 19%; p=0.031) at 12 weeks. In the group of patients randomized to the CB-CAPs/MAP testing, two-tiered test results associated significantly with initiation of prednisone (50% Tier-1 positive and 14% Tier-2 positive vs. 3% Tier-2 negative, p=0.034) and a similar trend was observed in the initiation of hydroxychloroquine (HCQ) (50% Tier-1 positive and 29% Tier-2 positive vs. 11% Tier-2 negative, p=0.112). Initiation of prednisone and HCQ also associated with two-tiered positive test results in the group of patients randomized to SDLT (blinded group) (p=0.020 and p=0.054, respectively).

Conclusion: The decrease in the likelihood of SLE in both study arms following testing is consistent with the low prevalence of the disease. CB-CAPs/MAP was more effective than SDLT in allowing the physician to determine that SLE is an unlikely diagnosis. In addition, positive CB-CAPs/MAP test results impacted treatment management.

Wallace et al ACR 2019_table

« Back to 2019 ACR/ARP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/a-randomized-prospective-trial-to-assess-the-clinical-utility-of-multianalyte-assay-with-complement-activation-products-in-diagnosing-systemic-lupus-erythematosus/