[Concordance between thick blood smear, immunochromatography and polymerase chain reaction for malaria diagnosis]

Abstract

Introduction: The rapid and effective diagnosis of malaria is the determining condition for an appropriate treatment and control of the disease.

Objective: The sensitivity, specificity and the positive and negative predictive values were evaluated in cases of suspected malaria in Colombia in a comparison of a rapid diagnostic test. the PCR test and the thick blood smear-the traditional gold standard.

Materials and methods: A group of 100 patients with symptoms compatible with malaria, were included in the study. They were selected from the following Colombian regions: Urabá, Córdoba, lower Cauca, and relatively fewer from other malaria endemic areas of Colombia including the provinces of Valle, Chocó in the central west of Colombia and Vichada to the east. To each patient the following three tests were performed: the rapid OptiMAL test, the PCR identification and the thick blood smear. The PCR amplified specific DNA sequences with primers designed to identify the genus Plasmodium, and the two species present in Colombia, P. falciparum and P. vivax.

Results: The sensitivity of the rapid test versus the thick smear, for the diagnosis of both species of Plasmodium was 93.9% (95% CI: 87-100%) and the specificity was 94.3% (95% CI:.253 85-100%). The PCR compared with the thick smear showed a sensitivity of 100% (95% CI: 99-100%) and a specificity of 97.1% (95% CI: 90-100%).

Conclusions: The sensitivity and specificity of the three tests did not present statistically significant differences. However, the thick blood smear was recommended as the standard test, mainly due to its low cost.