Dados do Trabalho

Título

Performance and Pitfalls of Immunochromatographic Test for Chagas Disease Screening

Objetivo (s)

To evaluate two immunochromatographic tests (IC): SD Bioline Chagas AB® (Abbott, USA) and WL Check Chagas® (Wiener Lab, Rosario, Argentina) as alternatives for Chagas disease diagnosis and to determine whether the type of material (serum or whole blood) and storage conditions affect the results.

Material e Métodos

Frozen serum samples from 155 individuals (94 seropositives and 61 seronegatives) obtained during the diagnosis of patients with the indeterminate form of the disease, and fresh samples (serum and whole blood obtained from finger prick) from 50 individuals (42 seropositives and 8 seronegatives) during the confirmation of the diagnosis.

Resultados e Conclusão

The results showed a high agreement (Kappa coefficient) between the two kits, with fresh samples (k = 0.89 and k = 0.96 for samples obtained by finger prick and serum, respectively) and with frozen samples (k = 0.92). Sensitivity was better with fresh serum compared to frozen serum (100% vs 79.8% for Abbott and 97.6% vs 80.6% for Wiener IC tests, respectively). Thawing cycles may interfere with the amount of antibodies for immunochromatographic detection. For the fresh samples, the use of serum samples was slightly advantageous in relation to finger prick with Abbott IC (sensitivity of 93.3%), but better than Wiener (sensitivity of 80.6%). This difference could be due to the quantity of whole blood obtained by finger prick and migration of the sample from capillary to the solid support. However, the false-negative results observed with the two IC tests corresponded to samples with ELISA results with an absorbance/cutoff (A/C) ratio < 3, indicating that they are not the most reliable for disease detection, as high antibody levels (A/C > 5) seem to be correlated with disease progression. Conclusions: These tests are easy to manipulate, have short execution time and do not require apparatus for incubation, centrifugation, or mechanical reading, being usefull especially in remote areas with limited resources. Performing two tests for diagnosis seems unnecessary, as the correlation between the kits was high and the Abbott IC kit had better sensitivity. Despite finger prick samples showing slightly lower sensitivity compared to serum, they are a good alternative due to the ease of collection and the absence of the need for specialized personnel. However, the costs of IC are similar to or higher than serology, and this should be considered when evaluating the advantages of their use.

Palavras-chave

Chagas Disease, Diagnosis. Rapid tests, pitfalls

Agradecimentos

NIH