Psoriatic arthritis

Call to align PBS criteria for bDMARDs with international PsA guidelines

Disease outcomes are good for patients with psoriatic arthritis  (PsA) who meet PBS criteria for bDMARD treatment, but these criteria exclude many patients who do not respond to conventional synthetic DMARDs, Australian research shows.

In a study of 105 consecutive PsA patients seen at a South Australian clinic, half (n=53) met the PBS criteria for bDMARD treatment, which are derived from RA criteria and focus only on joints and serum markers of inflammation, CRP or erythrocyte sedimentation rate (ESR).

In this group of bDMARD treated patients, 39 (74%) achieved minimal disease activity (MDA) compared to only 17 of 52 (33%) patients in the ineligible group who were treated with csDMARDs such as methotrexate.

The study investigators led by Dr Eliza Pontifex at the Department of Rheumatology, Flinders Medical Centre, Adelaide, said the findings showed that PBS criteria were specific  for selecting  good responders to bDMARD therapy, but they were at variance with other international guidelines for PsA.

They noted a surprising lack of difference between their biologic clinic PsA and RA patient cohorts in terms of the pattern of active joints at the time they qualified for a bDMARD.

Likewise, regardless of treatment, there was no difference in inflammatory marker levels between those who did and did not achieve MDA.

Enthesitis was present in 30.5% of study participants overall, but only 10 (19%) patients with enthesitis were on bDMARDs and 22 (42%) were not, indicating that those not on bDMARDs were twice as likely to have any enthesitis.

In contrast to PBS criteria, international guidelines for PsA from groups such as EULAR and GRAPPA  support the use of bDMARDs early in the disease phase (prior to use of csDMARDs) in patients with severe peripheral arthritis with features of poor prognosis such as high joint counts and high inflammatory markers.

“With the current Australian PBS bDMARD prescribing criteria, those at the greatest disadvantage are patients with severe enthesitis. There is an argument therefore, for considering making bDMARDs available for this indication, if it is resistant to other therapies and impairing function,” they suggested.

“Enthesitis radiological biomarkers are under development and validation, and could assist in assessment of severity and treatment response. This would bring Australian treatment options in line with expert guidelines, and offer relief to the small number of PsA patients for whom this is a big issue,” they concluded.

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