B-274 Leveraging Dried Blood Spots (DBS) for Universal Lead Screening in Children

Abstract Background In 2016, nearly 600,000 children in the United States, aged 1 to 5 years, had whole blood (WB) lead levels of 3.5 µg/dL or higher. Since no level of lead exposure is considered safe — particularly in children — several states have implemented universal blood lead screening for this age group. Currently, the most common specimen types for lead testing are capillary and venous whole blood, both of which require a visit to a phlebotomy facility. At home sample collection could significantly improve compliance and success of universal screening programs. The study objective was to develop and validate a method for lead analysis using Inductively Coupled Plasma -Tandem Mass Spectrometry (ICP-MS/MS) in dried blood spot (DBS) samples, offering a convenient and accessible alternative to traditional specimen collection. Methods Pooled-negative lead spiked samples, quality control (QC) samples, proficiency testing (PT) samples from the College of American Pathologists (CAP), and remnant positive and negative patient WB samples were used to prepare DBS. 20 µL samples were applied to dried blood spot (DBS) cassettes and allowed to dry overnight. Each DBS was placed in a metal-free tube and 200 µL of extraction solvent consisting of 1% ethanol, 5% ammonium hydroxide, .02% triton x, and .01% nitric acid was added. The samples were vortexed for 1 minute and centrifuged at 3000 rpm for 5 minutes. Following centrifugation, 2.8 mL of 0.5% nitric acid were added to the samples and analyzed using ICP-MS/MS (Agilent 8900). The analysis was performed in collision/reaction cell (CRC) mode with oxygen gas. All study samples were quantified using matrix-matched calibrators with Iridium (Ir) as internal standard to minimize matrix effects and ensure accuracy. Results DBS from 30 different spiked samples were tested in duplicates. Average percent recovery of samples at 0.5 µg/dL, samples between 2.3 and 7.3 µg/dL, and between 28 and 35 µg/dL, were 34% (range: 20% to 68%), 113% (range: 95% to 127%), and 111% (range: 47%-141%), respectively. Average percent recovery of DBS with blood lead CAP PT samples with peer mean values of 4.643, 9.729, 24.587, and 49.311 µg/dL was 102% (range 89-112%) across 3 independent analyses done in duplicates. Between day precision of QCs (average: 2.568, 13.470, and 35.590 µg/dL) were less than 10%. The Deming regression analysis of 30 patients’ WB samples and DBS created from the remnant samples revealed a slope of 1.324; intercept of 0.212; R of 0.8486, with Deming standard error estimate of 2.0263. The DBS method was linear from 0.5-35 µ g/dL, with slope of 0.978 and intercept of 0.2430, when analyzed by EP Evaluator, with allowable total error of 2 mcg/dL or 10%. Conclusion Lead analysis of DBS offers a promising alternative to traditional blood collection, with good accuracy, precision, and recovery at concentrations near the blood lead reference value of 3.5 ug/dL. Ultimately, enabling at-home sample collection could enhance early detection, and contribute to better health outcomes, especially for young children, who are disproportionately vulnerable to the harmful effects of lead exposure.