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Establish the diagnosis of Plasmodium or other parasitic infection; diagnose malarial parasitic infestation of blood; evaluate febrile disease of unknown origin.
One negative result does not rule out the possibility of parasitic infestation. If protozoal, filarial, or trypanosomal infection is strongly suspected, test should be performed at least three times with samples obtained at different times in the fever cycle.
Proper therapy depends on identification of the specific variety of malaria parasite. Release of trophozoites and RBC debris results in a febrile response. Periodicity of fever correlates with type of malaria (see table). Organisms are most likely to be detected just before onset of fever, which is predictable in many cases. Sampling immediately upon onset of fever is the most desirable time to obtain blood. Alternatively, in cases negative by these means but with a strong clinical history, multiple sampling at different times in the fever cycle may prove successful.
Changes in Infected RBCs Useful to Identify Malaria Species
|
Plasmodium Species |
Infected RBC Enlarged |
Presence of Schüffner Dots |
Presence of Maurer Dots |
Multiple Parasites per RBC |
Parasite With Double Chromatin Dots |
Parasite With Sausage- Shaped Gametocytes |
|---|---|---|---|---|---|---|
|
P vivax |
+ |
+ |
— |
Rare |
Rare |
— |
|
P falciparum |
— |
— |
+ |
+ |
+ |
+ |
|
P ovale |
± |
+ |
— |
— |
— |
— |
|
P malariae |
— |
— |
+ |
— |
— |
— |
Friedman MJ, Trager W. The biochemistry of resistance to malaria. Sci Am. 1981 Mar, 244(3):154-155,158-164. PubMed 6163210
Henry JB, Nelson DA, Tomar RH, et al. Clinical Diagnosis and Management by Laboratory Methods. 18th ed. Philadelphia, Pa: WB Saunders Co;1991:1168-1172.
Makler MT, Gibbins B. Laboratory diagnosis of malaria. Clin Lab Med. 1991 Dec; 11(4):941-956. PubMed 1802530
