Comparison of performance characteristics of two immunoassays in the detection of antigenic components of plasmodium falciparum in blood from yemeni patients

Abstract AR

Objectives .: The purpose of the study was to compare the performance characteristics of two immunochromatographic antigen detection systems for the diagnosis of Plasmodium falciparum in an attempt to detect the parasite components in blood samples from Yemeni patients.

Methods: The traditional microscopic examination was performed to identify the cases of malaria and subsequently two immunoassays were compared: OptiMAL (R) detects parasite lactate dehydrogenase (pLDH) and Core ™ detects parasite histidine rich protein-2 (pHRP-2) in blood samples using monoclonal antibodies.

During the study period, blood samples from 518 cases of suspected malaria were collected from hospitals in Taiz (214) and Hodeidah (304) and examined microscopically.

All cases that were found positive for falciparum malaria were subsequently examined by the indicated immunoassays.

In addition, 87 blood samples from healthy individuals and 47 from subjects with heterologous infections were tested by the same immunoassays in order to assess sensitivity and specificity.

Results: Of 518 cases suspected of malaria, 171 (33%) were positive for trophozoites and/or gametocytes in the blood films examined.

Among them, the rate of infection in Taiz was 27% and in Hodeidah 37%, (P= 0.02).

Of 171 positive blood samples, 164 were positive by the OptiMAL immunoassay giving 96% sensitivity.

Specificity of this test was 100% as none of the heterologous infections was positive.

The Core immunoassay was able to detect pHRP-2 in 159 of 171 tested blood samples to give a 93% sensitivity.

This test showed cross reactivity with blood samples from patients with toxoplasmosis giving 94% specificity.

Nineteen of the parasitologically confirmed cases were classified as negative by the two immunoassays (7 with OptiMAL and 12 with Core).

Conclusion: The newer generation antigen detection systems have a high degree of sensitivity and specificity.

This makes such systems a promising tool for diagnosis of falciparum malaria in Yemen.