Quantification of Urinary Melamine Among Urolithiasis in Taiwan by Liquid Chromatography/Tandem Mass Spectrometry

Abstract

PP-29-152 Background/Aims: Recently, the outbreak of melamine-tainted formula for infants result in the adverse renal outcomes in young children had been reported in China. However, there is no report whether ingestion of melamine-tainted milk or other related products can cause adult urolithiasis. Thus, the present study was designed to investigate the association between urinary melamine concentration and the risk of urolithiasis in Taiwan population. Methods: Between 2003 and 2007, we had 11 patients with upper urinary tract uric acid urolithiasis and 22 sex- and age-matched calcium urolithiasis and controls individually from Kaohsiung Medical University Hospital. A triple quadrupole liquid chromatography tandem mass spectrometry (LC-MS/MS) method is presented for the quantitative determination of urinary melamine concentration. Wilcoxon rank sum test was used to compare the urinary melamine concentrations in uric acid urolithiasis with controls as well as in calcium urolithiasis with controls. FDR (false discovery rate) was used to correct the P values for 2 comparisons. Results: Our results show that subjects 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. We also noted a significant increasing trend of risk across controls, calcium and uric acid urolithiasis on urinary melamine concentration (trend test, P = 0.006). 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. Conclusion: This 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. We will further apply to more comprehend study to investigate the potential health effects of urolithiasis contributed by melamine-tainted dairy products.