05 February 2013

How is malaria diagnosed?

Identifying the parasite in a blood sample confirms the diagnosis.

 Malaria should be suspected in the following circumstances:

•    when a person has periodic attacks of chills and fever with no apparent cause
•    if within the previous year the person had visited an area where malaria is prevalent. Any person who has a fever and who has been to a malaria area recently should be screened for malaria.
•    if the spleen is enlarged, or there is jaundice or anaemia without an obvious cause.

Identifying the parasite in a blood sample confirms the diagnosis. Blood is taken, smeared onto a slide, stained, and examined under a microscope. More than one sample may be needed to make the diagnosis because the level of parasites in the blood varies over time. The laboratory will (whenever possible) identify the species of Plasmodium, because the treatment, complications, and prognosis vary depending on the species involved.

Recently, new diagnostic tests have become available. The most commonly used of these is a test that detects one of the malarial proteins in the blood. The advantage of this test is that it can be done in clinics with relatively little training. However, it is probably not as sensitive as the examination of smears, and it cannot identify the different forms of malaria.

(Dr Andrew Whitelaw, MBBCh (Witwatersrand), MSc (UCT), FCPath (Micro) (SA) Pathologist, Department of Microbiology, University of Cape Town/National Laboratory Services)


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