A preliminary comparative report of quantitative buffy coat and modified quantitative buffy coat with peripheral blood smear in malaria diagnosis

Abstract

The quantitative buffy coat (QBC) technique is a method of diagnosing malarial parasites based on micro-centrifugation, fluorescence, and density gradient of infected red blood cells. The aim of the present study was to modify the QBC technique in order to reduce the cost per test of malaria diagnosis. This was achieved by introducing some modifications to routine QBC wherein REMI centrifuge (cost Rs 19 000/–) and ultra-violet microscope (Rs 115 000) were used instead of parafuge (Rs 108 000) and paralens (Rs 293 625/–). With the above modification, the cost per test for laboratories dealing with high patient load was reduced by 13%, whereas for smaller laboratories with low patient load, the cost per test was reduced by 48%. This is a significant difference in cost. The results of the modified QBC method were compared with the current diagnostic methods: peripheral blood smear (PBS) and routine QBC. Blood samples collected from 96 patients were subjected to the above tests. Considering PBS as the gold standard, routine QBC showed 91% sensitivity and 96% specificity for Plasmodium vivax- and 91% sensitivity and 94% specificity for Plasmodium falciparum-infected patients. It was seen that the modified QBC technique had 91% sensitivity and 98% specificity for P. vivax and 91% sensitivity and 96% specificity for P. falciparum. It was concluded that modification of the QBC technique renders it cheaper without compromising the specificity and sensitivity of the method.

Keywords:

• Malaria
• Plasmodium falciparum
• Plasmodium vivax
• Quantitative buffy coat
• Thick and thin smears

We acknowledge Dr Girish Patwardhan, Director of Liliac Medicare Ltd, for providing QBC tubes and Paraviewer for carrying out the study.