Specimen Requirements

Alternate Specimen Requirements

Minimum Specimen Requirements

Stability

Days Performed

7 days a week

Turnaround Time

1 - 2 days

Methodology

Special Info

Malaria is a potentially life-threatening condition, and testing for this infection should be conducted as quickly as possible. Consequently, this test is not recommended as the primary screening method when specimens can be delivered within a few hours of collection. Laboratories that cannot ensure prompt specimen delivery should first conduct an initial screening for malaria and other blood parasites, such as a malaria antigen test, before sending the specimen for further analysis. This test is used to confirm a presumptive malaria diagnosis, identify the infecting Plasmodium and Babesia species, and determine the percent parasitemia. A percent parasitemia calculated more than 8 hours after blood collection may not accurately reflect the patient's current state of parasitemia. Additionally, if malaria parasites have degraded or their morphology has altered due to specimen age or suboptimal transportation conditions, the calculation of percent parasitemia may be either impossible or inaccurate.

Clinical Info

Malaria is a mosquito-borne disease caused by Plasmodium parasites, which are a major cause of illness and death globally. Malaria can also affect travelers from non-endemic areas. The primary Plasmodium species responsible for malaria are P. falciparum, P. vivax, P. malariae, and P. ovale. P. knowlesi, a simian parasite, has also been known to infect humans in parts of Southeast Asia and is significant due to its potential to cause severe illness. P. falciparum is particularly concerning due to its resistance to many antimalarial drugs. In the U.S., Babesia microti is the main cause of human cases, with notable outbreaks in the Northeast and Midwest. Other species like Babesia duncani and Babesia divergens have also been reported in certain areas. Babesia microti is nationally notifiable. Babesia microti shares its tick vector with Borrelia burgdorferi (Lyme disease) and Anaplasma phagocytophilum (human granulocytic anaplasmosis), making concurrent testing for these diseases advisable in endemic regions. Additionally, babesiosis can be transmitted via blood transfusion, prompting the FDA to mandate donor screening for this parasite in 2018. While most cases of babesiosis are mild or asymptomatic, severe cases can occur, particularly in asplenic individuals. Thick film microscopy, is used for screening, while thin films help determine percent parasitemia, which indicates the severity and helps monitor treatment response. Percent parasitemia is calculated from microscopic fields on the thin blood film. Percent parasitemia exclude malarial gametocytes as they are not infectious and are not targeted by most antimalarial treatments and will be reported out within the comments. Microfilaria, Trypanosomes if seen will be reported but alternate molecular or serological testing is recommended.

Clinical Limitation

A single negative result does not exclude the possibility of parasitic infection. If there is strong suspicion testing should be conducted at least three times using samples collected at different times throughout the fever cycle. Delay in sample processing or transport can impact quality of smears thus the sensitivity and specificity of blood parasite detection. Testing can not be performed on grossly hemolysed, or clotted blood specimens.

Clinical Reference

1. Centers for Disease Control (CDC). Evaluation and diagnosis of Malaria, June 24, 2024. https://www.cdc.gov/malaria/hcp/clinical-guidance/evaluation-diagnosis.html 2. Bobbi S. Pritt, 2023. Plasmodium and Babesia, p.13-20. Manual of Clinical Microbiology, 13th Edition. ASM Press, Washington, DC. 3. Mathison BA, Pritt BS. Update on malaria diagnostics and test utilization. J Clin Microbiol. 2017;55(7):2009-2017