Health & body · 2021
Could a rapid test backed up by dried blood samples make community screening for more practical?
The findings support a proposed approach: use the easier-to-use rapid test first, then check negative results with dried-blood E-CLIA. The rapid test had 89.6% , compared with 97% for dried-blood E-CLIA; both had 100% .
Details
Chagas disease is a public health problem in Latin America and, because of migration, in other regions including Spain. Conventional serological diagnosis requires an invasive sample—plasma or serum—and a well-equipped laboratory. Blood dried on filter paper, known as dried blood spots (DBS), or a rapid diagnostic test (RDT) could offer practical alternatives to the reference protocol for serological screening in epidemiological studies. The researchers evaluated dried blood sampling and the Trypanosoma Detect™ rapid diagnostic test for detecting antibodies against T. cruzi in community-based screening.
This retrospective diagnostic evaluation included 162 stored paired whole-blood and serum samples from Latin American migrants, along with 25 negative-control blood samples. Chronic Chagas disease was diagnosed using serum according to WHO algorithms. Blood samples were retrospectively collected as dried spots and analyzed using two serological techniques: enzyme-linked immunosorbent assay (ELISA) and electrochemiluminescence immunoassay (E-CLIA). Whole-blood samples were also used to evaluate a rapid diagnostic test based on immunochromatography.
Dried-blood eluates showed better agreement with conventional serum testing when analyzed using E-CLIA rather than ELISA, with sensitivities of 97% and 77%, respectively. Both assays had 100% specificity. Median E-CLIA cut-off index values were significantly lower for dried blood than for serum: 138.1 versus 243.3 (P<0.05). Trypanosoma Detect™ had a sensitivity of 89.6% and a specificity of 100%.
The researchers concluded that E-CLIA detects antibodies against T. cruzi in dried blood with higher sensitivity than ELISA. Trypanosoma Detect™ is easier to use but has lower sensitivity than dried-blood E-CLIA. They therefore proposed a sequential strategy for community Chagas disease screening programs: perform the rapid test first, then check negative results with DBS-ECLIA.
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