Rheumatoid Arthritis Diagnostic and Monitoring Testing Patterns by Physicians and Advanced Practice Providers in the...

To investigate longitudinal trends in rheumatoid arthritis (RA) diagnosis and monitoring by physicians and advanced practice providers (APPs) as measured by laboratory testing.

We conducted a retrospective review of RA-associated diagnostic and monitoring tests ordered through Labcorp by 7,026 physicians and 2,188 APPs in primary care and rheumatology between 2012 and 2024. Diagnostic tests include conventional markers (rheumatoid factor and anti-cyclic citrullinated peptide) and emerging markers (14.3.3 eta protein, anti-citrullinated α-enolase peptide 1, anti-carbamylated protein, and anti-citrullinated vimentin antibodies). Panel tests combine these markers to enhance diagnostic accuracy. Monitoring tests include the Vectra tests.

From 2012 to 2024, rheumatology APPs who consistently ordered RA-associated tests annually through Labcorp increased by 411.8%, whereas rheumatology physicians who consistently ordered RA-associated tests through Labcorp grew by 58.5%. Compared with rheumatology physicians, rheumatology APPs ordered 37.9 fewer conventional markers (P = 2.7 × 10^-12) and 2.4 more monitoring tests (P = 0.019). Between 2012 and 2024, conventional marker volumes increased by 3.0% among rheumatology physicians, 98.9% among rheumatology APPs, 36.2% among primary care physicians, and 75.6% among primary care APPs. The yearly average volume of RA panel tests ordered by rheumatology APPs increased by 2,948.5% compared with increases of 218.4% by rheumatology physicians, 128.0% by primary care physicians, and 203.7% by primary care APPs. The difference in the proportion of positive diagnostic test results between rheumatology physicians and rheumatology APPs narrowed from 3.0% in 2015 to 0.5% in 2024.

We observed a rise in APP contributions to RA-diagnostic and RA-monitoring test ordering, consistent with their growing presence within the rheumatology workforce.