Diagnosis
Malaria should not be diagnosed based on symptoms alone, because the symptoms are not sufficiently specific and an alternative cause could easily be missed, with potentially severe consequences for the patient. If at all possible malaria should be diagnosed based on the identification of parasites in the patient’s blood either by examination of a blood smear by a skilled microscopist or by testing a drop of blood using an appropriate rapid diagnostic test (RDT).Microscopy takes longer than an RDT because the blood slide must be stained and dried before it can be examined under a microscope. Malaria microscopy is however the most reliable way of diagnosing a malaria infection as it can detect lower parasite concentrations than RDTs, provided that the slide is well stained and examined by a skilled microscopist. However, if the technician’s skills are not of the highest quality, RDTs may be much more reliable than microscopy for detecting malaria.
An RDT is around the size of a home pregnancy test and works in a similar way, though it tests a drop of blood rather than urine. A drop of blood drawn from a pricked finger is dotted onto the test strip with some diluent and after a few minutes the strip shows whether the blood is positive or negative for malaria. Some tests show whether the malaria is falciparum, or another of the malaria types.
Many types of RDTs are available with varying levels of performance. The tests which are able to differentiate between falciparum and non-falciparum malaria infections are less reliable and more expensive than the falciparum only tests; this is a critical problem in the Asia-Pacific region where falciparum and vivax malaria are both widely distributed. Microscopy is therefore the recommended diagnostic approach throughout the region. In rare instances test results may be falsely negative (usually when infections are light or patients have already received some antimalarial treatment). Therefore a clinical diagnosis of malaria can be made by a skilled clinician based on a detailed assessment after ruling out alternative causes of disease.
ADDITIONAL RESOURCES
on malaria diagnosis, treatment and drug resistance