Abstract
Detection of Plasmodium species by microscopy has been the gold standard for diagnosis of malaria for more than a century. Despite the fact that there is a significant decline in the number of positive cases reported from microscopy, antimalarial drugs prescriptions are on continuous increase as patients present with symptoms of malaria. This makes it difficult to establish accuracy, sensitivity and specificity of light microscopy in diagnosis of malaria in epidemic areas. This study was designed to compare microscopy with polymerase chain reaction as diagnostic methods for malaria in three epidemic areas in Kenya. A total of 356 patients presenting with malaria symptoms were diagnosed by microscopy and dried blood filter paper spots were collected from patient in Kisii, West Pokot and Narok districts. Plasmodium falciparum DNA was extracted from the dried blood filter samples. Primers specific for the Plasmodium Species were designed and used in a two step amplification of the Pfmdr gene. The PCR products were analyzed in ethidium bromide stained 1.5% agarose gel. It was found that 72 out of 350 specimens diagnosed as negative were positive for P. falciparum by nested PCR, while 6 which were microscopy positive were confirmed so by nested PCR. This study demonstrates that there is a high level of misdiagnosis which may either lead to denial for deserved treatment or undeserved treatment. Nested PCR detection of malaria parasites is a very useful complement to microscopy although it is expensive and takes long time. Additionally, smear negative patients suspected to have malaria should be subjected to PCR diagnosis to improve rational drug use. The economic burden of misdiagnosis and mistreatment of malaria outweighs that of PCR diagnosis, hence this diagnostic mode could be tenable in the long run even in rural areas.
Highlights
Malaria, a tropical disease caused by protozoan parasites of the genus Plasmodium is one of the most important infectious diseases in the world (Breman, 2001)
Examination of the thick and thin blood smear is the 'gold standard' for diagnosing malaria, important advances have been made in diagnostic testing, including fluorescence microscopy of parasite nuclei stained with acridine orange, rapid dipstick immunoassay, and polymerase chain reaction (PCR) assays
It was found that 350 patients were P. falciparum negative and 6 positive by microscopy
Summary
A tropical disease caused by protozoan parasites of the genus Plasmodium is one of the most important infectious diseases in the world (Breman, 2001). Accurate and specific methods of diagnosis are important in proper treatment. Examination of the thick and thin blood smear is the 'gold standard' for diagnosing malaria, important advances have been made in diagnostic testing, including fluorescence microscopy of parasite nuclei stained with acridine orange, rapid dipstick immunoassay, and polymerase chain reaction (PCR) assays. Diagnosis based on polymerase chain reaction for species-specific Plasmodium genome are the most accurate, sensitive and specific compared to diagnostic methods, and are capable of detecting as few as 10 parasites/μl of blood (Hanschield, and Grobusch, 2002). In developing world where malaria is highly prevalent, the resources to aid in proper diagnosis are lacking (Rafael et al, 2006) This lack of resources to aid proper and accurate diagnosis of P. falciparum has lead to improper administration of anti-malarials
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