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Indian Journal of Medical Microbiology, (2015) 33(1): 63-67
Original Article
Usefulness of a centrifuged buffy coat smear examination for diagnosis of malaria *S Mohanty, R Sharma, M Deb
Abstract Purpose: Malaria continues to be a global public health challenge. Microscopic examination of peripheral blood smear (PBS) is the standard method for malaria diagnosis, which is easily available and has low cost but its reliability is questionable at low level of parasitaemia. The present study was undertaken to assess the usefulness of a modified centrifuged buffy coat smear (CBCS) technique for diagnosis of malaria and to compare it with conventional PBS examination and antigen detection test. Materials and Methods: The study was carried out over a 6-month period from July to December 2011. Blood samples (2–3 ml per patient) collected in EDTAvials from patients with a clinical suspicion of malaria were subjected to all three tests, that is PBS, CBCS and antigen test and results were compared with antigen test as the gold standard. Result: Of 1655 samples received, 394 (23.8%) samples were positive for infection with malaria parasites. All the three tests detected malaria infection equally in 279 samples, and gave varied results in the remaining 115 samples. Addition of centrifugation (i.e. CBCS) to the conventional method of PBS enabled detection of 80 more cases of plasmodia infection, especially (43, 53.7%) at low levels of parasitaemia (1000 parasites/μl. However, at lower levels of parasitaemia (60 Total
Table 3: Demographic profile of malaria-positive patients (n=394) under study OPD (number of patients) Ward (number of patients) Male Female Male Female Mixed Mixed Mixed Mixed P. v P. f P. v P. f P. v P. f P. v P. f 6 0 0 2 0 0 51 32 0 45 32 1 14 7 0 6 3 1 57 61 2 28 41 2 0 0 0 0 0 0 1 1 0 0 1 0 20 7 0 8 3 1 109 94 2 73 74 3
OPD: Outpatient department, P. v: Plasmodium vivax, P. f: Plasmodium falciparum www.ijmm.org
66
Indian Journal of Medical Microbiology
Table 4: Sensitivity, specificity and validity of PBS and CBCS in comparison to antigen test Test Sensitivity Specificity PPV NPV AUC* (%) (%) (%) (%) PBS 72.9 99.7 98.9 92.4 0.84 CBCS 91.9 99.2 97.2 97.6 0.93 PBS: Peripheral blood smear, CBCS: Centrifuged buffy coat smear, PPV: Positive predictive value, NPV: Negative predictive value, AUC: Area under the curve. *P
Indian Journal of Medical Microbiology, (2015) 33(1): 63-67
Original Article
Usefulness of a centrifuged buffy coat smear examination for diagnosis of malaria *S Mohanty, R Sharma, M Deb
Abstract Purpose: Malaria continues to be a global public health challenge. Microscopic examination of peripheral blood smear (PBS) is the standard method for malaria diagnosis, which is easily available and has low cost but its reliability is questionable at low level of parasitaemia. The present study was undertaken to assess the usefulness of a modified centrifuged buffy coat smear (CBCS) technique for diagnosis of malaria and to compare it with conventional PBS examination and antigen detection test. Materials and Methods: The study was carried out over a 6-month period from July to December 2011. Blood samples (2–3 ml per patient) collected in EDTAvials from patients with a clinical suspicion of malaria were subjected to all three tests, that is PBS, CBCS and antigen test and results were compared with antigen test as the gold standard. Result: Of 1655 samples received, 394 (23.8%) samples were positive for infection with malaria parasites. All the three tests detected malaria infection equally in 279 samples, and gave varied results in the remaining 115 samples. Addition of centrifugation (i.e. CBCS) to the conventional method of PBS enabled detection of 80 more cases of plasmodia infection, especially (43, 53.7%) at low levels of parasitaemia (1000 parasites/μl. However, at lower levels of parasitaemia (60 Total
Table 3: Demographic profile of malaria-positive patients (n=394) under study OPD (number of patients) Ward (number of patients) Male Female Male Female Mixed Mixed Mixed Mixed P. v P. f P. v P. f P. v P. f P. v P. f 6 0 0 2 0 0 51 32 0 45 32 1 14 7 0 6 3 1 57 61 2 28 41 2 0 0 0 0 0 0 1 1 0 0 1 0 20 7 0 8 3 1 109 94 2 73 74 3
OPD: Outpatient department, P. v: Plasmodium vivax, P. f: Plasmodium falciparum www.ijmm.org
66
Indian Journal of Medical Microbiology
Table 4: Sensitivity, specificity and validity of PBS and CBCS in comparison to antigen test Test Sensitivity Specificity PPV NPV AUC* (%) (%) (%) (%) PBS 72.9 99.7 98.9 92.4 0.84 CBCS 91.9 99.2 97.2 97.6 0.93 PBS: Peripheral blood smear, CBCS: Centrifuged buffy coat smear, PPV: Positive predictive value, NPV: Negative predictive value, AUC: Area under the curve. *P
