Parasite Examination, Whole Blood

Smears made from fresh whole capillary (fingerstick) blood and/or capillary blood in EDTA (Microtainer™), or 3 to 5 mL fresh whole venous blood in EDTA

Films (two thin and two thick) or 3 to 5 mL fresh whole venous blood in EDTA

Glass slide, lavender-top (EDTA) tube

Prepare sterile venipuncture site

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.

Wright stain; microscopic examination of thick and thin peripheral blood smears stained with Romanovsky dye (in particular Giemsa). Thick films are more difficult to interpret but greatly increase sensitivity (by concentrating cells and organisms). Thick smears require considerable experience with malaria, as they increase the number of cells examined in a given time period by a factor of about 12.¹

No organisms identified

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.