Urinary melamine and adult urolithiasis in Taiwan

BackgroundThis study aims to investigate the association between urinary melamine concentration and the risk of urolithiasis in adult.MethodsFrom 2003 to 2007, 11 and 22 patients diagnosed with upper urinary tract uric acid urolithiasis and calcium urolithiasis, respectively, were recruited from Kaohsiung Medical University Hospital. For comparison, we randomly collected 22 sex- and age-matched subjects who come to the same hospital for regular health check-up at the same period of time. Urinary melamine concentration was measured by the method of triple-quadrupole liquid chromatography tandem mass spectrometry (LC-MS/MS). Wilcoxon rank sum test was used to compare the urinary melamine concentrations in uric acid urolithiasis patients with controls as well as in calcium urolithiasis patients with controls. FDR (false discovery rate) was used to correct the p-values for two comparisons.ResultsSubjects with uric acid urolithiasis (median: 0.50 vs 0.06 μg/mmol creatinine, Wilcoxon test: FDR_p = 0.024) and with calcium urolithiasis (median: 0.14 vs 0.06, FDR_p = 0.024) had significantly higher urinary melamine concentration than controls. Based on the ROC curves, subjects whose melamine levels were over 0.262 and 0.037 μg/mmol creatinine, respectively, might have significant risks to have uric acid and calcium urolithiasis.ConclusionThis preliminary study suggests that exposure to even low-dose melamine-related products still have the potential to develop both uric acid and calcium urolithiasis in adults.