Validation of a particle gel immunoassay for Trypanosoma cruzi antibody detection using plasma samples collected with capillary tubes.

INTRODUCTION The Chagas disease particle gel immunoassay (PaGIA-Chagas) is a simple, fast and practical test used for the diagnosis of the chronic Chagas disease and is based on anti-Trypanosoma cruzi antibody detection in serum. This study aimed to validate the PaGIA-Chagas on plasma collected with capillary tubes. METHODOLOGY Serum samples from 74 T. cruzi-infected and 26 non-infected individuals were tested by conventional indirect immunofluorescence and PaGIA-Chagas. Later, plasma specimens collected with capillary tubes from these same individuals were tested by PaGIA-Chagas. Results from serum samples tested by IFA and PAGIA- Chagas were considered as the reference standard to determine the accuracy parameters of the particle gel tested on plasma samples. The inter-test agreement of T. cruzi antibody detection by PaGIA-Chagas on serum and plasma was calculated using Kappa index. RESULTS The PaGIA-Chagas performed on plasma collected with capillary tubes had sensitivity and specificity of 99% and 100%, respectively. The crude agreement observed with the results of the PaGIA-Chagas on plasma and serum was 99% and the Kappa index was 0.975 (CI95%: 0.782 - 1.000). CONCLUSION PaGIA-Chagas for anti-T. cruzi detection on plasma collected with capillary tubes is accurate and might be indicated to reduce fieldwork time and materials in epidemiological screening of chronic Chagas disease.