A probiotic did not improve psoriatic arthritis activity

Design

Single-centre, double-blind, placebo-controlled RCT

Population

66 adults with moderately active psoriatic arthritis on stable therapy

Primary outcome

PASDAS ≤3.2 at week 12 without treatment change

Effect

43% vs 65%; OR 0.4 (0.13–1.18)

In this single-centre, double-blind, placebo-controlled trial, 66 patients with moderately active psoriatic arthritis on stable treatment were randomised to a multispecies Lactobacillus and Bifidobacterium probiotic or placebo for 12 weeks.

Low disease activity or remission without treatment change was reached by 43% on probiotic and 65% on placebo (OR 0.4, 95% CI 0.13–1.18; p = 0.17). There were no differences in gut permeability markers, immune cells or stool microbiome composition, and no serious product-related adverse events.

The trial was small, but the direction did not favour the probiotic and the proposed mechanism did not move. Patients frequently ask about probiotics for inflammatory arthritis; this gives clinicians evidence to discuss.

• Probiotics did not improve psoriatic arthritis activity in this trial.
• Gut permeability and microbiome composition did not change with the probiotic.
• Advise patients that probiotics are not a substitute for, or add-on to, disease-modifying treatment on current evidence.
• The probiotic was well tolerated.

Why it matters

The gut–joint axis is a popular idea with patients; this is a direct test of one product.

Don't overread it

Small, single-centre and 12 weeks; other probiotic formulations were not tested.

The statistics, in plain English

An odds ratio of 0.4 with an interval from 0.13 to 1.18 crosses 1, so the difference could be chance — but if anything, it pointed away from the probiotic.

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