Method Comparison of Dried Blood Spot and Plasma Apolipoprotein B Measurement on a Semi-Automated Analyser: Toward...

Apolipoprotein B (ApoB) is a key marker of atherogenic lipoprotein burden, but conventional plasma-based testing requires venous sampling and centralized laboratory infrastructure. Dried blood spot (DBS) sampling offers a minimally invasive alternative suitable for decentralized settings. This study evaluated the analytical performance of a DBS-based ApoB assay on the Chem7 semi-automated analyser and compared it with the Abbott ARCHITECT ci4100 plasma reference method. DBS samples prepared from 50 de-identified EDTA whole-blood specimens were extracted in saline and analysed using an immunoturbidimetric ApoB assay on the Chem7 analyser with a correction factor of 2 applied for haematocrit dilution. Paired plasma specimens were analysed on the ARCHITECT ci4100. Method comparison included Passing-Bablok and Deming regression and Bland-Altman analysis. Potential outliers were assessed using Grubbs' test (α = 0.05). Precision verification followed CLSI EP15-A3. Corrected DBS ApoB showed strong correlation with plasma values (r = 0.97; R ² = 0.94). Passing-Bablok regression showed a slope of 0.872 and intercept of 14.29 mg/dL, consistent with Deming regression. Bland-Altman analysis demonstrated a mean bias of -1.5 mg/dL with acceptable limits of agreement. Eighty percent of results were within ±10% of plasma values. No statistically significant outliers were identified, and precision estimates (within-day and between-day coefficients of variations (CVs) of 4.6% and 9.2%) met CLSI criteria. DBS-based ApoB measurement on the Chem7 analyser provides reliable, reproducible and clinically acceptable agreement with plasma testing, supporting its applicability in decentralized and resource-limited settings.