Comparison of capillary microsampling and venous blood for multi-pathogen serosurveillance.

Serosurveillance for vaccine-preventable diseases (VPDs) can inform public health strategies by identifying gaps in immunization programs. However, venous blood sampling, though reliable and sensitive for serosurveillance, presents logistical challenges in resource-limited settings. Capillary microsampling using dried blood spots (DBS) offers a simpler, less invasive alternative that reduces cold-chain and personnel requirements. This study evaluated the performance and stability of DBS collected on filter paper and Mitra microsamplers compared with venous plasma. IgG antibody levels against diphtheria, tetanus, pertussis, measles, mumps, rubella, and varicella were quantified using a validated fluorescent bead-based multiplex immunoassay. At baseline, strong agreement was observed between DBS and plasma, with ≥ 93% of observations within the 95% limits of agreement. Sensitivity was high (≥ 95.8%) for all pathogens except pertussis (72.2-77.8%). For DBS stored at - 20 °C with desiccants, agreement remained high at 90 days, with gradual declines observed beyond one year. At room temperature, IgG levels declined, with sensitivity ≥ 91.2% at 7 and 30 days but dropping below 90% by 90 days for several analytes. Beyond one year, IgG recovery was minimal, with sensitivity < 50% for most pathogens. These findings support DBS utility for VPD serosurveillance, with stability up to 90 days at - 20 °C and 30 days at room temperature.