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Rapid Responses: Rapid Responses published:
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Who should receive renal screening?
- I-Jen Wang, Tien-Jen Lin, Pau-Chung Chen (23 December 2008)
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Authors' reply
- Hugh S. Lam, Pak C. Ng (30 December 2008)
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Melamine tainted formula in Hong Kong
- Sam P Lau, FUNG K.P. (8 April 2009)
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I-Jen Wang, Visiting staff of Department of Pediatrics,Taipei Hospital, Department of Health Department of Health Risk Management, China Medical University, Taiwan, Tien-Jen Lin, Pau-Chung Chen
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In the context of renal screening,1 we are curious about the reason why the author mainly focused on children with low dose melamine exposure. It is thought that children with high dose exposure or history of residence in China might be excluded in this study. The author mentioned that it was almost impossible to accurately quantify patients' exposure to melamine, so their definition of children with low dose melamine exposure based on individual daily intake seems to be questionable. In addition, the incidence of nephrolithiasis cases might be underestimated in this study. Since most children were assessed some time after last notice of melamine exposure, some cases might have spontaneously passed out their stones already. Many more of the children might be affected with nephrolithiasis if evaluation was done while receiving contaminated formula. The author thought that renal screening in children with a history of exposure to low dose melamine is not necessary. But in our experience, we did find nephrolithiasis in the low dose exposure group. Furthermore, performing screening test seems to be crucial for early detection because most children with nephrolithiasis were symptomless. Although the screening test could not be considered as cost-effective because the low prevalence rate and the patientsˇ¦ symptoms were not so severe as in China, it did relieve parents from anxiety. In conclusion, we suggest both urinalysis and renal ultrasonography should be performed in all high risk children with history of having resided in China and consuming contaminated dairy products. I-Jen Wang,1 Tien-Jen Lin,2 Pau-Chung Chen3 1Taipei Hospital, Department of Health; China Medical University
Competing interests: None declared |
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Hugh S. Lam, Assistant Professor Department of Paediatrics, 6/F Clinical Sciences Building, Prince of Wales Hospital, N.T., Hong Kong, Pak C. Ng
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In response to Wang et al, we would like to restate that we recognize the limitations of our study in terms of melamine exposure estimation and timing of renal assessments. However, we were obviously not in control of how soon the children were assessed after cessation of melamine tainted product consumption. Although recall bias and possible overestimation of tainted milk consumption history by concerned parents is possible, we believe that as a population the children screened were genuinely exposed to melamine and as such the overall results do reflect the results of similarly affected populations outside of the Mainland of China. We did not restrict our focus to investigating children with low dose melamine exposure. In Hong Kong, any child with a history of continuous melamine tainted product consumption was eligible for screening if she or he was a Hong Kong resident, even those who may have been living in the Mainland. Our paper focused on reporting our short-term findings. We fully appreciate the limitations of such data, but as published data in human subjects is sparse, we believe that sharing our experience would help build some basis upon which public health decisions could be made in the long-term with regard to this catastrophe. We were very careful not to overinterpret our data. Further, our study has shown that urgent and large-scale renal assessments in Hong Kong have not resulted in any health benefits to the assessed children. We therefore postulate that urgent and large-scale screening of children exposed to low doses of melamine may not be cost-effective or informative. We believe that reporting the results of our cohort should help relieve parental anxiety. In contrast, we believe that providing and encouraging urgent screening for children with low dose melamine exposure may increase parental anxiety. Competing interests: None declared |
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Sam P Lau, private practitioner paediatrician Hong Kong, FUNG K.P.
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Dear Sir, Melamine related stone screening: An overlooked inference on tolerated daily intake We refer to the paper ‘Renal screening in children after exposure to low dose melamine in Hong Kong: cross sectional study’ published in the 18 Dec 2008 issue. Two important findings emerge from this study. A significantly high incidence of haematuria, lightly dismissed by the authors as insignificant, which alternatively may be an indication of minimal renal damage due to subclinical tubular damage or interstitial nephritis. The other more alarming aspect is the detection of stone formation with ‘safe’ consumption level (0.01-0.21 mg/kg/day); figures that are far below the so called tolerated daily intake (TDI) of 0.63mg/kg/day.1 The human renal stones are friable complexes of melamine and uric acids2 while those from animals are crystal precipitates of melamine and cyanurate.3 Thus the experience in Hong Kong suggests the TDI for infants could not be safely extrapolated from animal models. Since the exact mechanism of renal damage is still unclear, the logical conclusion as made obvious by this study is that any amount of melamine in infant food beyond environmental contamination is deemed unsafe for consumption and hence must be take off the shelves by legislation, as has been done in the US, EU and UK. Melamine simply should not be allowed in any infant formula. Unfortunately, our health authorities still regard infant formulae with melamine content of less than 1mg/kg as safe5; and hope that the magic figure of 0.63 is good enough to prevent a repeat of this tragic saga. This paper is a timely reminder for decision makers to seriously rethink their healthy policy. Sam P. Lau1, Kam Pui Fung2 1 Past-president of the Hong Kong Paediatric Society,708 Nan Fung Centre, Castle Peak Road, Hong Kong SAR, China, 2 Paediatrician, City Garden Paediatric Clinic, City Garden, Electric Road, Hong Kong SAR, China. References: 1. Interim melamine and analogues safety/risk assessment. U.S. Food and Drug Administration; 2007 May 25 Report. 2. Sun N, Shen Y, Sun Q, et al. Diagnosis and treatment of melamine- associated urinary calculus complicated with acute renal failure in infants and young children. Chin Med J 2009; 122:245-51. 3. Dobson RLM, Motlagh S, Quijano M, et al. Identification and characterization of toxicity of contaminants in pet food leading to an outbreak of renal toxicity in cats and dog. Toxicol Sci 2008;106:251-62. 4. Update interim safety and risk assessment of melamine and its analogues in food for humans. U.S. Food and Drug Administration; 2008 November 28. 5. Ho YY. Update on recent melamine-tainted milk/milk products incidents and its regulation. Hong Kong: Centre for Food Safety; 2008 September 24. Competing interests: None declared |
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