Clinical evaluation of flourescent in- situ hybridization (Fish) assay for malaria diagnosis

Abstract

Giemsa microscopy has played a major role in malaria control as a standard or reference method in diagnosis. However, this technique has varied performance characteristics while other techniques are more expensive. As a result, there is continued need for new and! or improved techniques that will increase ease of use and lower the cost of diagnosis. Fluorescent In-Situ Hybridization (FISH~ is a technique that uses fluorescent-labeled oligonucleotide probes that are specific to a region in Plasmodium species ribosomal (lSS) ribonucleic acid (rRNA) thus aiding detection of malaria parasites present in a blood sample. The aim of this study was to evaluate Fluorescent In-Situ Hybridization technique for diagnosis of uncomplicated malaria. Two hundred and sixteen patients visiting Tiwi Health Center, Coastal Kenya, suspected of having uncomplicated malaria were included in the study. Finger-prick blood samples were collected from the participants to be tested for malaria using Giemsa microscopy and Plasmodium genus ID-FIS~ test. The results were then used to determine the diagnostic performance of Plasmodium genus ID-FIS~ test against the Giemsa microscopy gold standard. The limit of detection of FISH® test was determined using cultured Plasmodium falciparum strain 06. Sensitivity and specificity were found to be 93% and 84% respectively giving a positive predictive value of 72% and a negative predictive value of 96%. The limit of detection provided additional evidence (higher detection rate of two logs) that Plasmodium genus FIS~ test is more sensitive than Giemsa microscopy. Plasmodium genus FISH® was found to be fast and easy to perform as well as more sensitive and specific than Giemsa microscopy. However, it is recommended that Plasmodium genus ID-FISH® is evaluated using a more sensitive and specific gold standard, like peR than Giemsa microscopy due to the high discrepancy observed in this study. Evaluation of Plasmodium genus ID-FISH® in malaria non-endemic sittings and its effect on the accuracy of anti-malaria drug efficacy studies are vital especially when the rate of low parasitemia cases have increased en route to malaria elimination in Kenya .