Background: Little is known about the exposure profiles of melamine in children. We evaluated the association of clinical findings, exposure patterns, and biomarkers with nephrolithiasis in children with potential exposure to melamine.
Methods: A case control study was conducted in children aged 0 to 16 years with potential exposure to contaminated dairy products. Cases were defined as nephrolithiasis detected by renal ultrasonography. On the basis of different brands of contaminated dairy products consumed, subjects were classified into high exposure, low exposure, and control groups with estimated melamine exposure levels of higher than 2.5ppm, 0.05-2.5ppm, and lower than detection limits <0.05ppm. We measured urine melamine for those with nephrolithiasis and age- and gender-matched controls within the subset of the study population.
Results: The duration of contaminated products consumption was longer in children with nephrolithiasis in the high exposure group than controls [median (IQR) 12.0 (3.3-24.0) vs. 6.0 (4.0-7.0) months; p=0.048]. High melamine exposure levels were significantly associated with nephrolithiasis [OR: 61.04 (95%CI: 12.73-292.84)]. The risk was found to increase with estimate melamine exposure levels (p for trend <0.001). Two among ten affected subjects with nephrolithiasis showed elevated urine melamine levels .In comparison, levels of all twenty controls were lower than the detection limit.
Conclusions: The risk of melamine associated nephrolithiasis was related with duration of contaminated products consumption and estimate melamine exposure levels. Though urine melamine was not a sensitive test, it might serve as an exposure biomarker in melamine associated nephrolithiasis.