Analysis of a novel field dilution method for testing samples that exceed the analytic range of point-of-care blood lead analyzers.

Investigators developed and evaluated a dilution method for the LeadCare II analyzer (LCII) for blood lead levels >65 μg/dL, the analyzer’s maximum reporting value. Venous blood samples from lead-poisoned children were initially analyzed in the field using the dilution method. Split samples were analyzed at the US Centers for Disease Control and Prevention (CDC) laboratory using both the dilution method and inductively coupled plasma-mass spectrometry (ICP-MS). The concordance correlation coefficient of CDC LCII vs. ICP-MS values (N = 211) was 0.976 (95 % confidence interval (CI) 0.970–0.981); of Field LCII vs. ICP-MS (N = 68) was 0.910 (95% CI 0.861–0.942), and CDC LCII vs. Field LCII (N = 53) was 0.721 (95% CI 0.565–0.827). Sixty percent of CDC and 54% of Field LCII values were within ±10% of the ICP-MS value. Results from the dilution method approximated ICP-MS values and were useful for field-based decision-making. Specific recommendations for additional evaluation are provided.