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 ~  Abstract
 ~  Materials and Me...
 ~  Results
 ~  Discussion
 ~  References

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BRIEF COMMUNICATION
Year : 2004  |  Volume : 22  |  Issue : 2  |  Page : 104-106
 

Comparison of parasite lactate dehydrogenase based immunochromatographic antigen detection assay (optimal) with microscopy for detection of malaria parasites


Apex Diagnostics and Research Centre, Jobra Road, Cuttack - 753 003, Orissa, India

Correspondence Address:
Apex Diagnostics and Research Centre, Jobra Road, Cuttack - 753 003, Orissa, India

 ~ Abstract 

This study was done to compare the ability of a newly developed rapid malaria test OPtiMAL, an immunochromatographic antigen detection assay for the diagnosis of malaria using parasite lactate dehydrogenase, against standard microscopy. Blood samples were obtained from 232 patients suspected of having malaria. A total of 122 samples (52.5%) were positive by blood films while 118 (50.8%) were positive by OPtiMAL test. The blood film indicated that 21.4% (26 of 122) of the patients were positive for P. falciparum and 78.6% (96 of 122) were infected with P. vivax. OPtiMAL test showed that 21.2% (25 of 118) were positive for P.falciparum and 78.8% (93 of 118) were infected with P. vivax. This assay had sensitivities of 88.4% and 96.8% compared to traditional blood films for detection of P.falciparum and P.vivax malaria respectively. Thus OPtiMAL test can be used with or without traditional blood film examination for detection of both P. vivax and P. falciparum malaria and can be effectively used for the rapid diagnosis of malaria.

How to cite this article:
Chayani N, Das B, Sur M, Bajoria S. Comparison of parasite lactate dehydrogenase based immunochromatographic antigen detection assay (optimal) with microscopy for detection of malaria parasites. Indian J Med Microbiol 2004;22:104-6


How to cite this URL:
Chayani N, Das B, Sur M, Bajoria S. Comparison of parasite lactate dehydrogenase based immunochromatographic antigen detection assay (optimal) with microscopy for detection of malaria parasites. Indian J Med Microbiol [serial online] 2004 [cited 2019 Sep 22];22:104-6. Available from: http://www.ijmm.org/text.asp?2004/22/2/104/8081


Microscopic examination of blood smears is the widely used routine method for detection of malaria parasite and remains the gold standard for malaria diagnosis.[1] But microscopic examination is laborious and requires considerable expertise for its interpretation, particularly at low levels of parasitaemia. In addition, in patients with plasmodium falciparum malaria, sometimes the parasites can be sequestered and are not present in peripheral blood. Thus a P. falciparum infection could be missed due to absence of the parasite in a blood film. Besides these, majority of malaria cases occur in rural areas where there is little or no access to reference laboratories and in many areas microscopy is not available. Keeping all these in mind a study was done to compare microscopic examination of blood film with newly developed simple dipstick antigen-capture assay which detects the presence of parasite lactate dehydrogenase (PLDH) antigen of malaria parasite in lysed whole blood sample. The PLDH first binds to a gold labeled antibody particle. This complex then migrates up the test strip where it is captured by an immobilized second antibody. A visual ab-ag-ab complex is then formed at the reaction site.

 ~ Materials and Methods Top

This study included 232 patients attending Apex Diagnostics and Research Centre from the month of February 2002 to June 2002. The patients were referred to us for investigation of malaria by different clinicians. Sixty percent of patients had history suggestive of malaria i.e., rigor, chill, rise of high temperature with profuse sweating. Another 40% gave the history of irregular fever, joint pain and Jaundice. From each patient venous blood was collected into a sterile tube containing potassium EDTA. Thin and thick smear blood films were made on site at the time of specimen collection. Thin and thick smear blood films were stained with Giemsa stain and were examined for malaria parasite by light microscopy. All the slides were examined independently by two microscopists. When there was a difference of opinion a third microscopist's opinion was taken into account. According to standard practice, a thin blood smear was examined for 15 minutes and for a thick blood film 200 fields were visualized. All whole blood samples were tested with the OPtiMAL test (parasite lactate dehydrogenase based immunochromato-graphic antigen detection assay) according to manufacturer's instructions. Interpretation of the assay test srip results was done as below.
i) When one control band and two test bands appeared the test was considered to be positive for P. falciparum.
ii) When one control band and one test band appeared the test was considered positive for P.vivax.
iii) When only control band appeared at the top of the test strip without test band the test was considered to be negative.

 ~ Results Top

A total of 232 blood samples were tested for malaria parasites by the OPtiMAL method and the results were compared to those obtained from examination of thin and thick smear blood film. The blood film results indicated that 122 (52.5%) patients were infected with malaria and the rest 110 (47.5%) were malaria negative. Among the positive patients P. vivax was detected in 96 cases (78.6%) and P.falciparum in 26 cases (21.4%). Correspondingly, the OPtiMAL test results indicated that 118 (50.8%) of the patient samples were positive for malaria parasites and 114 (49.2%) were malaria negative. Infection with P. vivax accounted for 78.8% (93 of 118) while infection with P. falciparum accounted for 21.2% (25 of 118). Both methods identified one patient with a mixed infection of P.vivax and P.falciparum.
The blood film examination identified three P.vivax positive samples that were not detected by the OPtiMAL test, however, there was 100% agreement between blood film results and OPtiMAL results for the other 93 samples containing P.vivax. Two cases of P. falciparum detected by OptiMAL were not detected by the blood films and three cases of P. falciparum detected by blood film were not detected by OPtiMAL method. OPtiMAL had sensitivities of 88.4% and 96.8% when compared to traditional blood films for detection of P.falciparum and P.vivax infections [Table].

 ~ Discussion Top

The resurgence of malaria has renewed interest in developing not only preventive measures, but also rapid diagnostic techniques. Several methods have been developed to supplement and replace the conventional microscopic method. The most promising new malaria diagnostics are the serological dipstick tests.[2] OPtiMAL is one amongst them. We employed this test and compared it with conventional smear examination for diagnosis of P.falciparum and P. vivax infection.
The antigen detection test identified 50.8% as malaria positive while the blood film identified 52.5% to be malaria positive. Some malaria infections detected by blood film were not detected by the OptiMAL test. This may be explained by the fact that increased awareness of malaria among the general public has led to a rampant misuse of antimalarial drugs in inadequate doses empirically for any fever. Since OPtiMAL detects PLDH which is produced only by living parasites, the blood samples judged negative by OPtiMAL may have been dead parasites and not yet cleared from the host.[3]
Three cases of P.vivax and P.falciparum detected by blood film were not detected by OPtiMAL. This may be due to insufficient enzyme production which occurs during early malarial infection or the patient blood samples contained parasites at concentration below the OptiMAL test's detection level.[4] Two blood samples in which OPtiMAL detected P.falciparum band were found to be negative in blood smear examination. This may be explained by the fact that P.falciparum can sometimes sequester and may not be present in circulating blood.[5]
In our study the sensitivity of OPtiMAL for P.falciparum and P.vivax was 88.4% and 96.8% respectively. This confirms the observation of Palmer et al in 1998. They had found a sensitivity of 88% for P.falciparum and 94% for P.vivax using OPtiMAL.[5] Cooke et al obtained a sensitivity of 91.3% for P. falciparum with OPtiMAL.[1]
This evaluation has shown that OPtiMAL is a simple, sensitive and effective diagnostic test for P. falciparum and P.vivax in countries where both species are present and where many patient need a 'fever screen'. The sensitivity of this test is very close to microscopic examination of blood smears but does not require highly skilled personnel to perform or interpret results. The test has the added advantage that it can detect all four Plasmodium species and can be used to follow the efficacy of drug therapy since it detects an enzyme produced only by living parasites. Although it has got a number of advantages one needs to keep in mind the cost of the test which may not be affordable by many. The high cost of the test may prevent its regular and routine use in many of the laboratories. However, it is a valuable adjunct at the time of emergency for rapid diagnosis, although microscopy remains the mainstay for the diagnosis of malaria for routine use in countries like India. 

 ~ References Top

1.Cooke AH, Chiodini PL, Doherty T, Moody AH, Rites J, Pinder M. Comparison of a Parasite Lactate Dehydrogenase based Immunochromatographic Antigen detection assay (OPtiMAL) with microscopy for the detection of malaria parasites in human blood samples. American J Trop Med Hyg 1999;60:173-176.  Back to cited text no. 1    
2.Singh N, Valecha N, Sharma VP. Malaria Diagnosis by field workers using an immunochromatographic test. Trans R. Soc Trop Med Hyg 1997;91:396-397.  Back to cited text no. 2    
3.Pinto MJW, Pereira NF, Rodrigues S, Kharangate NV, Verenkar MP. Rapid diagnosis of Falciparum malaria by detection of Plasmodium Falciparum HRP-2 Ag. JAPI 1999;47(11):1076-1078.  Back to cited text no. 3    
4.Moody A, Hunt-Cooke A, Gabbet E, Chiodini P. Performance of the OPtiMAL Malaria Antigen Capture dipstick for malaria diagnosis and treatment monitoring at the Hospital for Tropical diseases, London. British J Haematol 2000;109:891-894.  Back to cited text no. 4    
5.Palmer CL, Lindo JF, Klaskala WI, Quesada JA, Kaminsky R, Baum MK, Aager AL. Evaluation of the Optimal test for rapid diagnosis of Plasmodium vivax and Plasmodium falciparum malaria. J Clin Microbiol 1998;36:203-206.  Back to cited text no. 5    
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2004 - Indian Journal of Medical Microbiology
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