Karamat Ahmed Karamat, Masood Anwar, Muhammad Ashraf.
Evaluation of a new diagnostic method for malarial parasites in peripheral blood
Pak J Pathol Apr - Jun 2000;11(2):22-6.
Department of Haematology, Armed Forces Institute of Pathology, Rawalpindi

Malaria is considered as one of the most widely spread and prevalent disease of mankind. It is endemic in South-East Asia, Africa and many parts of the world. To diagnose acute malaria, demonstration of malarial parasite in blood film is mandatory. The thick film preparation has always been considered a gold standard but it has disadvantage of being time consuming and requires lot of experience. At the same time it is not helpful in the identification of the species of malaria parasite most of the time. Although Standard QBC technique is a reliable method for diagnosis of Malaria, it needs expensive equipment. The modified buffy coat preparation involves the examination of smear made from buffy coat and stained by Romanowsky stain. Centrifugation of EDTA mixed blood in microhaematocrit capillary tube concentrates infected red blood cells in buffy coat due to change in the density with an added advantage of identifying the species of the parasite. A study was carried out from July 97 to Aug 99 in hematology department of AFIP to compare modified buffy coat technique with traditional methods of thin and thick film examination. Initially, 42 samples of patients, reported negative for malaria parasite by lab technician on routine thin film examination, were processed for thin, thick and modified buffy coat analysis. Thick film and buffy coat preparation detected malaria parasite in 7 cases improving the positivity by 16.7% as compared to thin film examination which detected malaria parasite in 4 cases with improvement of only 9.52%. The species identification was in-conclusive in thick film but it was easily identifiable in both buffy coat and thin smears. Next 20 positive samples were analysed by serial doubling dilution with compatible non-infected blood. Thick film examination showed a consistent superiority over thin film for detection of malaria parasite by a factor of +2.5. However this method was not helpful in identification of species of malaria parasite. Modified Buffy coat technique, on the other hand, was four times more superior to thin film in detecting malaria parasite and this method was also helpful in identifying species of malaria parasite. However this method was somewhat inferior to thick film examination. This difference might be due to the cases of P. falciparum infection in which malaria parasite, especially gametocytes were not concentrated in buffy coat. Buffy coat method has definite advantage over the thick film preparation, but further work is needed to see whether its results can approach those of thick film in detecting malaria parasite.

Category: Parasitology
Keywords: Malaria. Plasmodium.

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