Background A higher risk of urolithiasis has been reported in gout patients. However, whether urate-lowering treatments, including both xanthine oxidase inhibotors and uricosuric agents, are beneficial to reduce the risk or urolithiasis in gout patients has not been examined.

Objectives To investigate the independent associations between urate-lowering treatment (ULT) and the risk of urolithiasis in incident gout patients.

Methods We conducted a nested case-control study based on the Taiwan National Health Insurance Research Database (NHIRD), which was used to identify 473,858 newly diagnosis gout patients during the period from January 1, 2000 through December 31, 2004. All these patients were followed until December 31, 2013. We considered patients who first diagnose incident urolithiasis after the date of entry cohort (gout onset) as cases and the diagnostic date was defined as index date. Each case was matched up to five eligible controls whose follow-up period included the case's index date by sex, birth of year and gout diagnosis year. And the index date of case was assigned to the matched controls. Odds ratios (ORs) and 95% confidence interval (CI) of urolithiasis associated with cumulative defined daily dose (cDDD) of xanthine oxidase inhibitor and uricosuric agents were main ourcome measures.

Results Gout patients with incident urolithiasis (n=32,654) occurring after the initial diagnosis of gout aged 20–79 were age- and sex-matched 1:5 to 163,270 gout patients without urolithiasis. After adjusting for age, sex, urbanization status, income, occupation, and pertinent drugs and comorbidities, the OR of urolithiasis associated with use of ULT among gout patients were 1.04 (95% CI 1.00 to 1.07) for those with 28–90 cDDD, 0.95 (95% confidence interval 0.91–0.99) for 91–365 cDDD and 0.77 (95% confidence interval 0.73–0.82) for >365 cDDD, compared with those with a cDDD <28. The OR (95% CI) for urolithiasis associated with xanthine oxidase inhibitor use was 0.94 (0.89–0.99) for 28–90 cDDD, 0.90 (0.84–0.97) for 91–365 cDDD and 0.73 (0.63–0.83) for >365 cDDD. For uriscouric agents, the OR (95% CI) for urolithiasis among those with 28–91, 91–365 and <365 cDDD were 1.04 (1.01, 1.08), 0.94 (0.90–0.98) and 0.78 (0.73–0.84), respectively.

Conclusions Higher ULT consumption was associated with a lower risk of urolithiasis. Xanthine oxidase inhibitors associated with reduced urolithiasis risk consistently across the range of consumption studied but for uricosuric agents inadequate cumulative dose results in a higher risk despite the risk reduced gradually with a higher cumulative dose.

Disclosure of Interest None declared