Evaluation of volumetric DBS for lead analysis using ICP-MS/MS: addressing matrix effects and hematocrit variability.

BACKGROUND: Lead testing in dried blood spots (DBS) offer a convenient alternative to venous blood draw; however, its adoption has been limited by variable extraction efficiency, matrix effects, and hematocrit-dependent recovery. To mitigate these challenges, we explored the utility of volumetric DBS (vDBS) cards, which are known to deposit a fixed volume of blood that gets analyzed. MATERIALS AND METHODS: Samples (quality control, proficiency testing, lead spiked, and patient samples that were positive for lead) were pipetted onto the backs of vDBS cards. Extracts were analyzed using Inductively Coupled Plasma-Tandem Mass Spectrometry in collision/reaction cell mode with oxygen gas. Deming regression analyses evaluated whole blood and vDBS analyzed with aqueous calibrators; vDBS analyzed with aqueous and DBS calibrators. Samples with varying hematocrit were assessed for impact on recovery. RESULTS: A comparison of vDBS cards (n = 119) prepared from previously tested and lead spiked samples, analyzed against aqueous calibrators and vDBS calibrators, showed linear results: slope 1.024 (95% CI: 0.998 to 1.051) and y-intercept -0.0204 (95% CI: -0.4287 to 0.3879). Bias noted between whole blood lead and vDBS lead samples with varying hematocrit levels was not statistically significant. CONCLUSION: vDBS can be analyzed without matrix-matched calibrators to simplify routine assessment.