Complement activation products vs standard ANA testing: Treatment outcomes, diagnosis, and economic impact (CAPSTONE)...

BACKGROUND: Systemic lupus erythematosus (SLE) is a complex clinical diagnosis historically aided by imperfect biomarkers. The advent of a multianalyte assay panel incorporating innovative cell-bound complement activation markers necessitates a comparison of its clinical utility to conventional autoantibodies for the diagnosis and treatment of SLE. OBJECTIVES: To compare the likelihood of SLE diagnosis, SLE treatment initiation, and the downstream impact on health care utilization among patients tested with AVISE Lupus (AVISE) vs standard-of-care laboratory testing with the traditional antinuclear antibody (ANA) testing strategy cohort (tANA). METHODS: An observational retrospective cohort study was conducted using electronic health record (EHR) data from the Illumination Health registry, which integrates EHR records from more than 300 rheumatologists across the US. Health records from January 2016 to December 2020 and administrative claims with cost data for a subset of patients linkable to the HealthCore Integrated Research Database and Medicare data were analyzed. The AVISE and tANA test results were classified as positive, negative, or indeterminate, and outcomes were stratified based on test results. Two cohorts were established: AVISE testing strategy and the tANA approach. Analyses included test impact on SLE diagnosis, treatment initiation, patterns of repeat testing, and downstream health care utilization. Multivariable logistic regression was used to estimate odds ratios (ORs) comparing the likelihood of SLE medication initiation and SLE diagnosis between the AVISE and tANA cohorts. RESULTS: The main cohort included 21,827 AVISE testing episodes and 22,778 tANA testing episodes. A total of 2,437 (11.2%) patients tested positive by AVISE compared with 5,364 (23.6%) of tANA positive patients. Among patients with no baseline prescription for SLE medication(s), patients with a positive AVISE test result were more likely to initiate SLE medications compared with tANA positive patients (43% vs 32%; OR = 1.57; 95% CI = 1.41-1.76). The treatment effect was larger in patients new to the practice within the preceding year (55% vs 33%; adjusted OR = 2.77; 95% CI = 2.31-3.32). AVISE positive patients were more than 5-fold more likely to be diagnosed with SLE, as compared with the tANA patients (31% vs 8%; OR = 5.11; 95% CI = 4.43-5.89), and similar in the new patient cohort (30% vs 6%; OR = 6.34; 95% CI = 5.12-7.86). Linked EHR-Medicare data revealed a greater decrease in posttest vs pretest mean annualized outpatient laboratory testing in AVISE negative (-$985; P < 0.0001) vs tANA negative (-$356; P < 0.0001) patients. A similar analysis in the EHR-HealthCore linked data revealed similar numerical trends as the Medicare data for outpatient laboratory testing but did not reach significance (P > 0.05). Cost comparisons in the categories of hospitalization, emergency department, outpatient imaging, and pharmacy costs did not yield significant differences. CONCLUSIONS: The significantly greater likelihood of SLE diagnosis and SLE medication initiation in AVISE positive vs tANA positive patients is consistent with improved clinical actionability, potentially shortening time to diagnosis. AVISE negative patients experienced a greater decrease in outpatient laboratory testing posttest relative to tANA negative patients, supporting the improved negative predictive value of AVISE vs tANA. DISCLOSURES: Mr O'Malley and Dr Zack are employed by Exagen Inc. Drs Curtis and Xie, Ms Su, and Ms Clinton are affiliated with the University of Alabama at Birmingham. Mr Haechung and Dr Grabner are employees of HealthCore, Inc., which received funding from Bendcare (owner of the Illumination Health Registry) for the conduct of parts of the study on which this manuscript is based. Exagen Inc. provided funding to Bendcare for the conduct of the study. Dr Grabner is also a shareholder of Anthem, Inc.