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

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 19000/-) and ultra-violet microscope (Rs 115000) were used instead of parafuge (Rs 108000) and paralens (Rs 293625/-). 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.

Age-dependent sex bias in clinical malarial disease in hypoendemic regions.

BACKGROUND AND OBJECTIVES: Experimental models show a male bias in murine malaria; however, extant literature on biases in human clinical malaria is inconclusive. Studies in hyperendemic areas document an absence of sexual dimorphism in clinical malaria. Data on sex bias in clinical malaria in hypoendemic areas is ambiguous--some reports note a male bias but do not investigate the role of differential mosquito exposure in that bias. Moreover, these studies do not examine whether the bias is age related. This study investigates whether clinical malaria in hypoendemic regions exhibits a sex bias and whether this bias is age-dependent. We also consider the role of vector exposure in this bias. METHODS: Retrospective passive clinical malaria datasets (2002-2007) and active surveillance datasets (2000-2009) were captured for the hypoendemic Mumbai region in Western India. To validate findings, passive retrospective data was captured from a primary malaria clinic (2006-2007) in hypoendemic Rourkela (Eastern India). Data was normalized by determining percent slide-positivity rates (SPRs) for males and females, and parasite-positivity distributions were established across age groups. The Mann-Whitney test, Wilcoxon Signed Rank test, and Chi-square analysis were used to determine statistical significances. RESULTS: In both the Mumbai and Rourkela regions, clinical malaria exhibited an adult male bias (p<0.01). A sex bias was not observed in children aged ≤10. Post-puberty, male SPRs were significantly greater than females SPRs (p<0.01). This adult male bias was observed for both vivax and falciparum clinical disease. Analysis of active surveillance data did not reveal an age or sex bias in the frequency of parasite positivity. CONCLUSION: This study demonstrates an age-dependent sex bias in clinical malaria in hypoendemic regions and enhanced incidence of clinical malaria in males following puberty. Possible roles of sex hormones, vector exposure, co-infections, and other factors in this enhanced susceptibility are discussed.