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Recall of a lead-contaminated vitamin and mineral supplement in a clinical trial
W J Rogan1, N B Ragan, A I Damokosh
1National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
Insights
Vitamin and mineral supplements given to children in the Treatment of Lead-exposed Children (TLC) trial were contaminated with lead. Blood lead levels were not detectably affected by this contamination.
Area of Science:
- Environmental Health
- Pediatric Toxicology
- Clinical Trials
Background:
- The Treatment of Lead-exposed Children (TLC) trial investigated developmental outcomes in children treated for lead poisoning.
- A critical incident occurred when vitamin and mineral supplements provided to all participants were found to be contaminated with lead.
Purpose of the Study:
- To assess the impact of lead-contaminated supplements on blood lead concentrations in children participating in the TLC trial.
- To determine if the contamination would affect the trial's primary objective regarding succimer treatment for lead poisoning.
Main Methods:
- Recalled contaminated supplements from participants.
- Measured children's blood lead levels after supplement distribution.
- Analyzed blood lead data to assess the effect of contamination and supplement consumption.
Main Results:
- The mean increase in blood lead was minimal in children who received contaminated supplements (0.06+/-0.01 micromol/L) compared to those who did not (0.09+/-0.03 micromol/L).
- No dose-response relationship was found between estimated supplement consumption and increased blood lead levels.
- Blood lead concentrations in the children were not detectably altered by the supplement contamination.
Conclusions:
- The lead contamination of supplements did not significantly impact children's blood lead concentrations.
- The TLC trial's findings on the efficacy of drug therapy for lead-induced cognitive delay remain valid.
- This incident highlights the importance of rigorous quality control in clinical trial supplies.
Purpose:
The Treatment of Lead-exposed Children (TLC) trial tested whether developmental outcome differed between children treated for lead poisoning with succimer or placebo. On 7 July 1997, TLC was informed that the vitamin and mineral supplements it gave to all children were contaminated with about 35 microg of lead per tablet.
Methods:
TLC recalled the contaminated supplements and measured the children's exposure.
Results:
The families of 96% of the children were contacted with 30 days. Among the 571 children to whom the contaminated supplements were dispensed, the mean increase in blood lead was 0.06+/-0.01 micromol/L (1.2+/-0.2 microg/dL); among 78 children to whom they were not, it was 0.09+/-0.03 micromol/L (1.8+/-0.7 microg/dL). There was no evidence of a dose-response relation between estimated supplement consumption and increase in blood lead concentration.
Conclusions:
The children's blood lead concentrations were not detectably affected by the contamination. Since the association of cognitive delay with lead exposure is best described for blood lead, we believe that the trial's inference about the effect of drug therapy on lead induced cognitive delay should be unaffected.
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