Parasight-F dipstick antigen test in the diagnosis of falciparum malaria in Ethiopia

Abstract

Objective: To determine the shelf life, rapidity and diagnostic performance of ParaSight-F.

Design: Prospective randomised study.

Settings: Malaria diagnostic and treatment posts and health centres in central-southern part of the Ethiopian Rift Valley.

Subjects: Three hundred and eighty two subjects randomly selected.

Main outcome measures: Double blind evaluation of the sensitivity, specificity and predictive values of PFT versus CBF.

Results: The point prevalence was found to be 29.7% with species dominance of P. falciparum to P. vivax in the ratio of 4:1. The ParaSight-F test showed, considering P. falciparum only, a sensitivity of 92.5% and specificity of 93%. A remarkably high positive predictive value (PPV) of 82% as well as a negative predictive value (NPV) of 99% was obtained. Considering all species of Plasmodium, sensitivity was 78.6% and specificity 93%, with PPV and NPV of 82% and 91% respectively. Moreover, PFT was found to be rapid with a batch of ten-strips--a rack completed in 30 to 50 minutes, which was five to six times faster than CBF reading. In shelf-life studies, after one year of storage at room temperature, results were found similar to the original readings, indicating the stability and long durability of the test strips.

Conclusion: In their durability and high diagnostic performances, both the microscopic slide readings and PFT were found comparable and interchangeable, and advantage in endemic areas where laboratory facilities are not available. The rapidity of PFT may be of greater value during malaria epidemics. But during non-epidemic seasons, the inability of PFT not to detect all forms of malaria remains a draw back.