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Test ID: LCMAL Malaria, Molecular Detection, PCR, Varies

Reporting Name

Malaria PCR

Useful For

Detection of Plasmodium DNA and identification of the infecting species

 

An adjunct to conventional microscopy of Giemsa-stained films, particularly in cases of low percent parasitemia or suboptimal parasite morphology

 

Detection and confirmatory identification of Plasmodium species: P falciparum, P vivax, P ovale, P malariae, and P knowlesi

 

This test should not be used to screen asymptomatic patients.

Clinical Information

Malaria is a mosquito-transmitted disease caused by apicomplexan parasites in the genus Plasmodium. It is an important cause of morbidity and mortality worldwide, with the World Health Organization (WHO) estimating 219 million cases and 435,000 malaria-related deaths in 2017. Malaria disproportionately affects individuals living in Africa (90% of cases), with individuals living in southeast Asia and the eastern Mediterranean regions next most affected. Malaria is also encountered outside of endemic regions such as the United States, usually in returning travelers.

 

Malaria is caused primarily by 4 species of the protozoa Plasmodium: P falciparum, P vivax, P malariae, and P ovale. A fifth Plasmodium species, P knowlesi, is a simian parasite that may be an important source of human infection in some regions of Southeast Asia. Differentiating P falciparum and P knowlesi from other species is important since both can cause life-threatening infections. In addition, P falciparum is typically resistant to many commonly used antimalarial agents such as chloroquine.

 

Microscopy of Giemsa-stained thick and thin blood films is the standard laboratory method for diagnosis and differentiation of malaria parasites. Under optimal conditions, the sensitivity of the thick film microscopy is estimated to be 10 to 30 parasites per microliter of blood. However, microscopic diagnosis requires considerable expertise and may be insensitive or nonspecific when inadequate training and facilities are available. Furthermore, prolonged exposure to EDTA, transportation conditions, and prior use of antimalarial drugs may alter parasite morphology and negatively impact the ability to perform species identification by microscopy. Finally, Babesia parasites have a similar appearance to P falciparum ring forms (early trophozoites) on peripheral blood films, resulting in potential diagnostic confusion.

 

PCR is an alternative method of malaria diagnosis that allows for sensitive and specific detection of Plasmodium species DNA from peripheral blood. PCR may be more sensitive than conventional microscopy in very low parasitemias, and is more specific for species identification. It may be particularly useful when subjective microscopy does not permit certain identification of the species present. Malaria PCR can be used in conjunction with a traditional blood film or Babesia PCR when the clinical or morphologic differential includes both babesiosis and malaria. Examination of the thin film also allows for calculation of percent parasitemia, which can be used to predict prognosis and monitor response to treatment. This test does not include blood smear examination or calculation of parasitemia.

Interpretation

A positive result indicates the presence of Plasmodium nucleic acid and melting curve analysis indicates the infecting species.

Testing Algorithm

See Malaria Laboratory Testing Algorithm in Special Instructions.

Analytic Time

Same day/1 day

Day(s) and Time(s) Performed

Monday through Sunday; Varies

Clinical Reference

1. Mathison BA, Pritt BS: Update on Malaria Diagnostics and Test Utilization. J Clin Microbiol. 2017 Jul;55(7):2009-2017

2. Swan H, Sloan L, Muyombwe A, et al: Evaluation of a real-time polymerase chain reaction assay for the diagnosis of malaria in patients from Thailand. Am J Trop Med Hyg 2005 Nov;73(5):850-854

3. World Health Organization Malaria Page: www.who.int/topics/malaria/en/

4. Cox-Singh J, Davis T, Lee K, et al: Plasmodium knowlesi malaria in humans is widely distributed and potentially life-threatening. Clin Infect Dis 2008 January 15;46(2):165-171

Method Name

Real-Time Polymerase Chain Reaction (PCR)/DNA Probe Hybridization

Specimen Type

Varies


Advisory Information


1. This test is not performed on a STAT basis and, therefore, should not be used as a primary screening test for malaria.

2. This test is used primarily for confirmation of a presumptive malaria diagnosis and determination of infecting Plasmodium species-particularly when the parasite morphology on traditional blood films is suboptimal.

3. Clients in the Rochester, MN area who are seeking a primary test for malaria and who can deliver the specimen within 4 hours of collection should order the MAL / Rapid Malaria/Babesia Smear, Varies.

4. Laboratories that are unable to deliver a specimen within 4 hours of collection should perform an initial screen for malaria and other blood parasites in their laboratory prior to sending a specimen to Mayo Clinic Laboratories.

5. This test does not include blood smear examination/calculation of parasitemia. If calculation of percent parasitemia is also desired for cases that are PCR positive for Plasmodium species, clients should order LMALP / Malaria PCR with Parasitemia Reflex, Varies.



Specimen Required


Both blood and slides are required.

 

Specimen Type: Blood

Container/Tube: Lavender top (EDTA)

Specimen Volume: 4 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Do not transfer blood to other containers. Send specimen in original tube.

 

Specimen Type: Blood films

Container/Tube: Clean, grease-free slides in plastic slide container

Specimen Volume: 2 thin blood films and 2 thick blood films

Collection Instructions:

1. Ideally, blood films should be made directly from uncoagulated blood acquired via fingerstick. However, EDTA anticoagulated blood is also acceptable.

2. Prepare thin blood films as follows:

a. Prepare a thin film with a "feathered edge" that is no more than a single cell thick.

b. Allow the film to thoroughly air dry and then fix by briefly immersing in either absolute or 95% methyl alcohol.

c. Allow to air dry after fixation.

3. Prepare thick blood films as follows:

a. Place a large drop of blood (approximately the size of a dime and preferably from a fingerstick) on a slide.

b. Using a corner of a second slide, spread the drop in a circular motion while applying firm pressure to literally scratch the blood onto the carrier slide. This technique allows the blood to dry quickly and adhere well to the slide. Use approximately 20 circular sweeps with the second slide. The drop of blood should be about the size of a quarter when finished.

c. Do not fix. Air dry thoroughly (approximately 45 minutes) before placing in transport container.


Specimen Minimum Volume

Blood: 1 mL
Slides: See Specimen Required.

Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Refrigerated (preferred) 7 days
  Ambient  7 days

Reference Values

Negative

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

87798

LOINC Code Information

Test ID Test Order Name Order LOINC Value
LCMAL Malaria PCR 47260-5

 

Result ID Test Result Name Result LOINC Value
87860 Malaria PCR 47260-5

Forms

If not ordering electronically, complete, print, and send a Microbiology Test Request (T244) with the specimen.

Mayo Clinic Laboratories | Neurology Catalog Additional Information:

mml-CNS-Infections, mml-Pediatric