Objective: The objective was to compare the diagnostic performance of two antigen capture tests, ParaSight-F test and Immunochromatographic test (ICT), for the diagnosis of Plasmodium falciparum malaria.
Design: A comparative study.
Setting: Burma Valley, Mutare District, Manicaland in Zimbabwe.
Subjects: Patients attending the local clinic with clinical signs and symptoms associated with malaria infection. A blood film was collected from the patient and at the same time blood for the ParaSight-F test and the ICT was collected too. A total of 123 patients were diagnosed using the ICT test, the ParaSight-F test and microscopy which was used as a "gold" standard.
Main outcome measures: True positives and negatives, false positives and negatives with reference to microscopy.
Results: The results indicate that ICT had a higher sensitivity (100%) than the ParaSight-F test (93.94%) but showing a lower specificity. The specificity for ICT (75%) is lower than the ParaSight-F test (81.2%) because of the presence of circulating P. falciparum histidine-rich protein-2 (PfHRP-2) in blood even after two weeks post treatment. Two slides that were negative for ParaSight-F tests showed positive on microscopy. However, 21 and 12 slides which were negative on microscopy, showed positive with ICT and ParaSight-F respectively. The fact that ICT detects very low quantities of PfHRP-2 puts it at a comparative advantage because it detects positives even at very low parasite rates.
Conclusion: The availability of these two antigen capture tests, which are easy to perform, will reduce the number of severe cases by providing early diagnosis. The tests will also reduce the number of unnecessary treatments and irrational use of antimalarials.