Suissa S, Suissa K, Hudson M, et al. - The results demonstrated a significantly decreased mortality with allopurinol treatment cannot be applied as evidence, nevertheless, mainly due to time-related biases that tend to greatly exaggerate the potential benefit of treatments. The ALL-HEART randomized trial, which is currently underway and assesses the effect of adding allopurinol to usual care (compared to no added treatment), will offer reliable data on mortality.

• Researchers distinguished 12 observational studies, of which 3 were affected by immortal time bias and 3 by immeasurable time bias, while the remaining 6 studies avoided these time-related biases.

• They observed reductions in all-cause mortality with allopurinol use among the studies with immortal time bias, with a pooled hazard ratio (HR) of death correlated with allopurinol of 0.71 (95% confidence interval [95% CI] 0.50–1.01), as well as in those with immeasurable time bias (pooled HR 0.62 [95% CI 0.56–0.67]).

• In this research, the 6 studies that avoided these biases showed a null effect of allopurinol on mortality (pooled HR 0.99 [95% CI 0.87–1.11]), though the lack of an analysis based on treatment adherence may have attenuated the effect.