Art and Science of Laboratory Medicine

Art and Science of Laboratory Medicine

Saturday, August 27, 2016

Laboratory Identification of Malaria Parasites

Microscopy

Microscopy (morphologic analysis) continues to be the "gold standard" for malaria diagnosis. Parasites may be visualized on both thick and thin blood smears stained with Giemsa, Wright, or Wright-Giemsa stains. Giemsa is the preferred stain, as it allows for detection of certain morphologic features (e.g. Sch├╝ffner’s dots, Maurer’s clefts, etc.) that may not be seen with the other two. Ideally, the thick smears are used to detect the presence of parasites while the thin smears are used for species-level identification. Quantification may be done on both thick and thin smears.

Molecular diagnosis

Morphologic characteristics of malaria parasites can determine a parasite species, however, microscopists may occasionally fail to differentiate between species in cases where morphologic characteristics overlap (especially Plasmodium vivax and P. ovale), as well as in cases where parasite morphology has been altered by drug treatment or improper storage of the sample. In such cases, the Plasmodium species can be determined by using confirmatory molecular diagnostic tests. In addition, molecular tests such as PCR can detect parasites in specimens where the parasitemia may be below the detectable level of blood film examination.


Antibody detection

Malaria antibody detection for clinical diagnosis is performed using the indirect fluorescent antibody (IFA) test. The IFA procedure can be used as a diagnostic tool to determine if a patient has been infected with Plasmodium. Because of the time required for development of antibody and also the persistence of antibodies, serologic testing is not practical for routine diagnosis of acute malaria. However, antibody detection may be useful for:
screening blood donors involved in cases of transfusion-induced malaria when the donor's parasitemia may be below the detectable level of blood film examination
testing a patient who has been recently treated for malaria but in whom the diagnosis is questioned

Read more:
CDC - DPDx - Malaria - Diagnostic Findings

Source: CDC

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