Table 2.

Covariate model for allopurinol and post-hoc analyses based on data collection site [29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63].

Reference Collection Site	Middle East			Multi-National			North America
	β	SE	p	β	SE	p	β	SE	p
Intercept	−46.36	20.18	0.051	−109.20	32.54	0.010	−102.39	32.47	0.014
Dose	0.36	0.07	0.001	0.36	0.07	0.001	0.36	0.07	0.001
Chronic kidney disease (CKD) diagnosis	27.62	12.71	0.062	27.62	12.71	0.062	27.62	12.71	0.062
Sample size	0.002	0.01	0.771	0.002	0.01	0.771	0.002	0.01	0.771
Follow-up (days)	0.03	0.02	0.090	0.03	0.02	0.090	0.03	0.02	0.090
Region
China	−26.39	4.91	0.001	36.45	11.98	0.016	29.65	10.99	0.027
Europe	−109.98	23.92	0.002	−47.14	14.28	0.011	−53.95	11.84	0.002
Japan	15.91	5.61	0.022	78.75	18.55	0.003	71.95	17.57	0.003
Middle Eastern	-	-	-	62.84	14.10	0.002	56.03	12.83	0.002
Multi-National	−62.84	14.10	0.002	-	-	-	-6.81	6.21	0.305
North America	−56.03	12.83	0.002	6.84	6.21	0.305	-	-	-
Proportion of males	−8.42	6.49	0.231	−8.42	6.49	0.231	−8.42	6.49	0.231

Legend. The covariate model used each clinical trial location as a reference group: n = 19, τ² = 7.32, I² residual (%) = 76.74, adjusted R² = 0.91. The dose-dependent serum uric acid-lowering effect was estimated while accounting for CKD status, sample size, length of follow-up, data collection site, and proportion of male participants. CKD was defined as eGFR < 60 mL/min/1.73 m², CrCl < 50 mL/min/1.73 m², or serum creatinine > 1.5 mg/dL. The proportion of male participants was categorized by the median score for all arms: 0 for less male-dominant arms and 1 for more male-dominant arms. Region refers to the site where clinical trials were conducted. Follow-up refers to the duration of the clinical trial.