Comparison of Cobas Plasma Separation Cards and Whatman filter paper cards versus conventional serum samples for anti-Trypansoma cruzi antibody detection

BACKGROUND: Diagnosis of chronic Trypanosoma cruzi infection relies on serological techniques using invasive blood samples (serum or plasma), which can be impractical in remote areas. Dried blood spot (DBS) sampling offer advantages over invasive samples in terms of ease of collection (finger prick), transport and storage. This study aimed to compare the performance of anti-T. cruzi antibody detection from DBS samples collected on two different devices: Whatman cards and Cobas Plasma Separation Cards (PSC). METHODOLOGY/PRINCIPAL FINDINGS: A prospective study using 382 paired serum and whole blood samples was conducted. Whole blood were used to obtain DBS collected on Whatman and PSC cards. All samples were tested for IgG anti-T. cruzi using the Elecsys Chagas assay, with serum serving as the gold standard. Both DBS collection systems showed high concordance with serum samples (>96%). However, antibody index values detected in DBS samples were lower than those detected in serum samples (p < 0.05). Qualitative results from DBS were highly concordant between the collection systems, with only two discrepancies (2/382), both positive on Whatman and negative on PSC. Antibody index values from Whatman-collected samples were higher than those from PSC-collected samples (median 96.45 vs. 63.33; p < 0.05). CONCLUSIONS/SIGNIFICANCE: DBS sampling is a feasible alternative to invasive blood collection, particularly in settings with limited access to health systems. Both DBS-collection devices showed high diagnostic accuracy; however, the lower antibody index values from PSC-collected samples may compromise the sensitivity of the technique in samples with a low antibody index.