Prevalence of minimal disease activity in Australian patients with Psoriatic Arthritis: Assessing the outcome of national funding criteria for biologic disease-modifying antirheumatic drug prescribing.

AIM: Discrepancies exist between international treatment guidelines and current Australian Pharmaceutical Benefits Scheme (PBS) criteria for funding biologic disease-modifying antirheumatic drug (bDMARD) prescribing in psoriatic arthritis (PsA). We aimed to determine the prevalence of minimal disease activity (MDA) achievement and differences in inflammatory marker levels between PsA patients who have and have not met the Australian PBS criteria for bDMARDs.

METHOD: Consecutive participants diagnosed with PsA were assessed for MDA components and serum inflammatory markers. For those on bDMARDs, joint counts and inflammatory markers at the time of bDMARD qualification were compared with matched rheumatoid arthritis (RA) controls.

RESULTS: Minimal disease activity was achieved by 56/105 participants overall. There were no differences in inflammatory marker levels or involved joint count patterns between the PsA and RA groups at the time of bDMARD qualification. Seventy-three percent of the 53 PsA patients on bDMARD achieved MDA, vs 33% in the non-bDMARD group (P < 0.001). More bDMARD than non-bDMARD patients achieved four out of seven MDA components. Of those with any enthesitis, its prevalence was higher in the non-bDMARD group (22 vs 10, P = 0.009). Regardless of treatment, there was no difference in inflammatory marker levels between those who did and did not achieve MDA.

CONCLUSION: The Australian PBS criteria, funding bDMARD prescribing for PsA, select well for MDA achievers. A high prevalence of MDA non-achievement remains in patients ineligible for bDMARD funding, and enthesitis in this population is more common. Inflammatory markers were not discriminators between treatment or MDA achievement groups.