Exploring patients' profiles associated with the resolution of acute calcium pyrophosphate arthritis treatedwith colchicine and prednisone: post hoc analysis of a randomized controlled trial.

Objective: The objective was to identify factors determining acute arthritis resolution and safety with colchicine and prednisone in acute calcium pyrophosphate (CPP) crystal arthritis.

Methods: We conducted a post hoc analysis of the COLCHICORT trial, which compared colchicine and prednisone for the treatment of acute CPP crystal arthritis, using a composite outcome of secondary endpoints of the primary analysis. Factors associated with the sustained arthritis resolution with prednisone or colchicine treatment on day 3, and the occurrence of gastrointestinal adverse events (AEs) with colchicine, were examined. Two different machine-learning approaches were used to identify independent factors associated with the efficacy outcome: multiple logistic regressions and a decision tree were used.

Results: In total, 43/89 (48.3%) of participants were considered definite responders. In univariable analysis, definitive responders were more often hospitalised for stroke (9/43) (p=0.04), had an age ≥ 80 years old (39/43)(p=0.045) and were dyslipidemic (25/43) (p=0.03), while poor responders were more commonly hospitalised to manage the acute arthritis episode (22/43) (p<0.001) In multiple logistic regression, acute arthritides of the wrists (OR 4.06 95%CI [1.21; 15.50.85]) were associated with arthritis resolution on day 3, while randomisation in the colchicine arm (OR 0.31 95%CI [0.11; 0.83]) and diuretic use (OR 0.23 95%CI [0.097; 0.95]), were associated with a poor treatment response. Hospital admission for acute arthritis, CRP levels and eGFR were decision tree nodes selected as crucial for predicting definitive flare resolution. Three candidate variables were identified in the multiple logistic regression model explaining the occurrence of gastrointestinal adverse events with colchicine: male sex (OR 0.33 95% CI (0.07; 1.29) and diabetes (OR 0.24 95%CI (0.030; 1.24)) seemed protective while statin use (OR 3.54 95%CI (0.83; 18.82) seemed associated with their occurrence.

Conclusion: This study identified factors associated with the definitive response to colchicine and prednisone treatment in acute CPP crystal arthritis. Colchicine was associated with poorer efficacy,and was impacted by a dual effect on its safety and efficacy by medications and associated conditions..