Analysis of gout remission definitions in a randomised controlled trial of colchicine prophylaxis for people with gout initiating allopurinol.

OBJECTIVE: To investigate the effect of colchicine prophylaxis on gout remission when commencing urate lowering therapy (ULT), and illness perceptions of people in remission, using two definitions of gout remission. METHODS: Data from a 12-month double-blind placebo-controlled trial of 200 people with gout commencing allopurinol were analyzed. Participants were randomly assigned to prophylaxis with 0.5mg daily colchicine or placebo for six months, followed by six months of additional follow-up. Gout remission was assessed using the 2016 preliminary definition or simplified definition without patient reported outcomes. Illness perceptions were assessed using a gout-specific brief illness perception questionnaire (BIPQ). RESULTS: In the first six months, few participants were in remission according to either the 2016 preliminary definition (3% for colchicine and 4% for placebo) or the simplified definition (7% for colchicine and 12% for placebo). In the second six months, after study drug (colchicine or placebo) discontinuation, fewer participants in the colchicine group than in the placebo group were in remission according to the 2016 preliminary definition (4% vs. 14%, p=0.03), and the simplified definition (14% vs 28%, p=0.02). Participants fulfilling remission using either definition had more favorable perceptions about their gout symptoms and illness concerns, as well as consequences, when using the simplified definition. CONCLUSION: Using either definition, six months of colchicine prophylaxis when initiating ULT does not provide an advantage in the fulfilment of gout remission. People fulfilling either definition report fewer symptoms, lower concern about their gout, and when using the simplified definition, are less affected by gout.

Predicting Gout Flares in People Starting Allopurinol Using the Start-Low Go-Slow Dose Escalation Strategy.

OBJECTIVE: The study objective was to determine predictors of gout flare when commencing allopurinol using the "start-low go-slow" dose escalation strategy. METHODS: A post hoc analysis of a 12-month double-blind placebo-controlled noninferiority trial with participants randomized 1:1 to colchicine 0.5 mg daily or placebo for the first six months was undertaken. Multivariate logistic regression models were used to identify independent predictors of gout flares in the first and last six months of the trial. RESULTS: Multivariable analysis revealed a significant association between risk of a gout flare in the first six months and flare in the month before starting allopurinol (odds ratio [OR] 2.65, 95% confidence interval [CI] 1.36-5.17) and allopurinol 100 mg starting dose (OR 3.21, 95% CI 1.41-7.27). The predictors of any gout flares in the last six months of the trial, after stopping colchicine or placebo, were having received colchicine (OR 2.95, 95% CI 1.48-5.86), at least one flare in the month before stopping study drug (OR 5.39, 95% CI 2.21-13.15), and serum urate ≥0.36 mmol/L at month 6 (OR 2.85, 95% CI 1.14-7.12). CONCLUSION: Anti-inflammatory prophylaxis when starting allopurinol using the "start-low go-slow" dose escalation strategy may be best targeted at those who have had a gout flare in the month before starting allopurinol and are commencing allopurinol 100 mg daily. For those with ongoing gout flares during the first six months of starting allopurinol who have not yet achieved serum urate target, a longer period of prophylaxis may be required.

The development and evaluation of dose-prediction tools for allopurinol therapy (Easy-Allo tools).

AIMS: Dose escalation at the initiation of allopurinol therapy can be protracted and resource intensive. Tools to predict the allopurinol doses required to achieve target serum urate concentrations would facilitate the implementation of more efficient dose-escalation strategies. The aim of this research was to develop and externally evaluate allopurinol dosing tools, one for use when the pre-urate-lowering therapy serum urate is known (Easy-Allo1) and one for when it is not known (Easy-Allo2). METHODS: A revised population pharmacokinetic-pharmacodynamic model was developed using data from 653 people with gout. Maintenance doses to achieve the serum urate target of <0.36 mmol L-1 in >80% of individuals were simulated and evaluated against external data. The predicted and observed allopurinol doses were compared using the mean prediction error (MPE) and root mean square error (RMSE). The proportion of Easy-Allo predicted doses within 100 mg of the observed was quantified. RESULTS: Allopurinol doses were predicted by total body weight, baseline urate, ethnicity and creatinine clearance. Easy-Allo1 produced unbiased and suitably precise dose predictions (MPE 2 mg day-1 95% confidence interval [CI] -13-17, RMSE 91%, 90% within 100 mg of the observed dose). Easy-Allo2 was positively biased by about 70 mg day-1 and slightly less precise (MPE 70 mg day-1 95% CI 52-88, RMSE 131%, 71% within 100 mg of the observed dose). CONCLUSIONS: The Easy-Allo tools provide a guide to the allopurinol maintenance dose requirement to achieve the serum urate target of <0.36 mmol L-1 and will aid in the development of novel dose-escalation strategies for allopurinol therapy.