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 0–16 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 2.5 ppm, 0.05–2.5 ppm and lower than detection limits <0.05 ppm. We measured urine melamine for those with nephrolithiasis and age-matched and gender-matched controls within the subset of the study population.
Results: The duration of consumption of contaminated products was longer in children with nephrolithiasis in the high exposure group than in 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 to 292.84)). The risk was found to increase with estimate melamine exposure levels (p for trend <0.001). Two among 10 affected subjects with nephrolithiasis showed elevated urine melamine levels. In comparison, levels of all 20 controls were lower than the detection limit.
Conclusions: The risk of melamine-associated nephrolithiasis was related to duration of consumption of contaminated products and estimated melamine exposure levels. Though urine melamine was not a sensitive test, it might serve as an exposure biomarker in melamine-associated nephrolithiasis.
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Funding This study was supported by grants from the National Science Council (NSC 97-2314-B-192-001-MY2) of Taiwan. The funding source had no role in the design or analysis of the study or in the decision to submit the manuscript for publication.
Competing interests None declared.
Provenance and Peer review Not commissioned; externally peer reviewed.
Ethics approval The study protocol was approved by the ethics review board in Taipei Hospital, Department of Health (No TH-IRB-08-07).
Contributors IJW drafted the manuscript and made substantial revisions. PCC, GL, KYW and CCC helped the study design and revise the manuscript. WCW and YNW designed the ultrasound follow-up service and provided the clinical and ultrasonography data. YJS, CLW and CFK coordinated the screening service. SLL designed the screening programme. WCC and TJL performed laboratory and statistical analysis. All authors read and critically commented on the paper. SLL is guarantor.