To diagnose malaria involves identifying the parasites (or the parasites antigen) in the victim’s blood. Diagnosis of malaria is subject to factors like
- The different malaria species which have different forms.
- The malaria parasites have different stages of erythrocytic schizogony.
- Each parasites with their own endemicity.
- Population movement.
- The problem of recurrent malaria.
- Resistance to drugs.
Type of Tests
Both Microscopic and non-microscopic tests are carried out to identify, confirm, diagnose malaria, monitor relapses and to determine drug effect on the parasite
Thick and thin blood smears
Prognosis of malaria entails performing blood smears where a drop of blood is applied to and spread onto a glass slide. It is then treated with a special stain and examined under a microscope for the morphology of infected blood cells and the parasite. Generally, thick smears and two thin smears are prepared. Those tests are currently the standard for malaria detection and identification. These examination is done by a trained and experienced laboratorian.
Thick smears are a greater sensitive test for malaria infection. A greater quantity of blood is examined under the microscope and the parasites are therefore much more likely to be seen. Thin smears have fewer blood cells present and allow identification of the type of Plasmodium species causing the infection. The number of infected red blood cells also can be calculated to determine the degree to which someone is infected (parasite load). This information is essential for proper treatment.
Rapid Diagnostic Tests (antigen testing) -RDT
when microscopy is not effectively available, rapid diagnostic tests can be used rather than blood smears. These tests detect malaria antigens (proteins) in a sample of someone’s blood (typically taken with a fingerstick) and indicate a positive result by a color change on the testing strip. Also known as “dipstick” tests.
There are different RDT’s available with varying capabilities in detecting the parasites. A test may detect P. falciparum, P. vivax, P. ovale, P. malariae but would not be able to distinguish between them. Some test may detect all species but tries to identify if a particular specie is present.
Molecular tests (Polymerase Chain Reaction (PCR))
The polymerase chain reaction is a laboratory approach that amplifies the parasite’s DNA and allows detection and identification of the Plasmodium species. This test can be used to confirm the diagnosis in laboratories where there may be a lack of training and experience in the microscopic examination for malaria. It can also be used to decide the Plasmodium species if the results of a blood smear are unclear. Likewise, it is useful for instances wherein the number of malaria parasites within the blood is low or whilst there are different types causing the infection (mixed) and examination the use of a microscope may be much less accurate. The cost of those molecular testing techniques limits their use in lots of areas in which malaria is endemic.
Antibody tests (serology).
Serology checks detect antibodies inside the blood which might be produced by the body in reaction to a malaria infection. They can’t diagnose an acute infection but assist determine if a person was previously exposed.
Some malarial parasites have become resistant to the drugs generally used to treat the infections. A few specialized laboratories can test the parasites from an infected individual to determine their drug susceptibility. This will be performed either by way of growing the parasites inside the presence of increasing amounts of the drug and observing the effect of the drug on the parasite
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