Evaluation of the Detection Threshold of Three Immonochromotographic Rapid Diagnostic Test (RDT) Kits for Falciparum Malaria Using Titration Technique

Abstract

The detection threshold of three immunochromatographic Rapid Diagnostic Test (RDT) Kits namely: HEXAGON MALARIA, ACCU-STAT MALARIA and SD-BIOLINE were studied using titration techniques. Parasitaemia values of pooled Plasmodium falciparum-positive specimens from 200 patients were determined. The samples were then prepared in 13 different dilutions and used to titrate the three RDT's in parallel in order to establish their detection threshold using the corresponding parasite density. Results showed that the average parasite density of these samples was 12,800 parasites per microlitre. HEXAGON MALARIA had a detection threshold of 50 matured parasites and 280 small trophozoites per microlitre, while SD-BIOLINE (Pv/Pf) and ACCU-STAT MALARIA recorded detection thresholds of 280 and 400 parasites per microlitre respectively, irrespective of the age and size of the parasites. Five of these patients gave positive results with all the three kits but were negative by microscopy. A mean count of 39 pigments per microlitre was obtained for these five patients. Both HEXAGON MALARIA and SD-BIOLINE had a detection threshold of 4 pigments per microlitre, while ACCU-STAT MALARIA had 20 pigments per microlitre. This suggests that these three kits have good detection thresholds and could therefore be suitable for mass screening for malaria parasites especially in malaria endemic areas where electricity, equipment and highly-skilled microscopists may be inadequate.

Keywords: Rapid Diagnostic kits, falciparum Malaria, Detection Threshold

Journal of Medical Laboratory Science Vol. 13 (2) 2004: pp. 45-50