Reproducibility of serological tests for the diagnosis of Trypanosoma cruzi infection in pregnant women in an endemic area of Santander, Colombia

Abstract

Introduction: The diagnosis of chronic Trypanosoma cruzi infection is supported by serological tests whose reproducibility has not been well documented.

Objective: To evaluate the reproducibility of the serological tests ELISA, IFAT and IHAT for the diagnosis of T. cruzi infection in pregnant women in an endemic zone in Santander.

Materials and methods: Through an evaluation study of diagnostic technologies, the reproducibility of the serological tests ELISA, IFAT and IHAT was determined in serum and eluted blood from pregnant women living in an endemic area for Chagas’ disease in Santander. The samples were selected by cross sectional sampling. The software Stata™ version 10.0 was used for statistical analysis. By means of the comparison of the highest kappa coefficient of each technique, the test with the best reproducibility was determined.

Results: A total of 777 samples were tested. In serum, ELISA (cutoff point: 0.3), IFAT (cutoff point: 1/32) and IHAT (cutoff point: 1/16) had kappa coefficients greater than 0.8 (0.98, 95% CI: 0.93-1.00; 0.98, 95% CI: 0.92-1.00 and 0.88, 95% CI: 0.74-0.97, respectively); no statistically significant differences among the three tests were found (p> 0.05). For the blood eluates, kappa coefficients were below 0.8 (highest kappa: 0.55, 95% CI: 0.41-0.68).

Conclusions: For the three serological tests using serum, the reproducibility determined by the kappa coefficient was perfect. Selecting any of them is useful for the diagnosis of T. cruzi infection. Given its simplicity and cost, the ELISA test is recommended for screening for this infection.