Federica Braga and coworkers [1] stated recently that hyperuricemia shows to be an independent predictor of coronary heart disease (CHD) risk (RR CHD = 1.206 [1.066-1.364]; RR CHD death = 1.209 [1.003-1.457]), mainly for the results found in women. That message seems to be of great importance: if it is true, the treatment of hyperuricemia should be included in the landscape of the therapeutic strategies to reduce the coronary risk. To ascertain the methodologic validity and robustness of that work, we considered it as a critical appraisal of some methodological aspects.In our approach, (a) we evaluated the overall quality of that systematic review through the AMSTAR checklist [2]; (b) we recovered the nine studies selected by Braga and colleagues [1] in order to repeat the meta-analysis and quantified the heterogeneity through I 2 statistic [3]; (c) we launched new subgroup and sensitivity and metaregression analyses in order to better explore the heterogeneity, considering the following as potential effect modifiers: gender, number of CHD covariates used in the adjustment models (i.e. age, BMI, total cholesterol or LDL-cholesterol or presence of dyslipidemia, blood pressure values or presence of hypertension, smoke, glucose values or presence of diabetes) and lack of nutritional information; (d) we estimated the prevalence of metabolic syndrome in single-trial samples using an Italian epidemiological research as reference sample [4]; (e) we investigated the quality of included trials and their risk of bias through the ACROBAT Cochrane checklist [5]; and (f) we used a generalized least-squares regression model to inspect some dose-response effect [6] both at trial level and with a doseresponse meta-analysis; the goodness of fit was explored with a χ 2 -test [7]. We restricted all our described analyses to the end point 'CHD incidence'; their methodological details are available in the online Supplementary material.
What were our results?1. The quality of the meta-analysis assessed with the AMSTAR checklist [2] appears to be medium/low: only 4/11 items were fully satisfied, 3/11 not satisfied and 4/11 uncertain. 2. The metaregression (Figure 1) demonstrates that the number of confounders could be an important cause of heterogeneity, with the risk ratio of CHD associated to hyperuricemia decreasing by 13% for each covariate added to the model (p = 0.056). The subgroup analysis using the number of covariates as effect modifier coherently indicates that the role of hyperuricemia tends to disappear in the best adjusted models (test of interaction, p = 0.056). Notably, the trials that were not adjusted for nutritional status [8][9][10]