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Malaria: Differential Diagnoses & Workup
Updated: May 29, 2009
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
- Multimedia
Differential Diagnoses
Other Problems to Be Considered
African trypanosomiasis
Amebiasis and amebic liver abscess
Brucellosis
Cholera
Collagen vascular disease
Enteric fever
Epidemic or louse-borne typhus
Food-borne illness or toxin
Hodgkin disease
Relapsing fever
Poliomyelitis
Schistosomiasis (acute Katayama fever)
Seizure disorder
HIV infection
Workup
Laboratory Studies
- Helpful studies include a CBC, electrolyte panel, renal function tests, pregnancy test, urinalysis, free serum haptoglobin, urine and blood cultures, and thick and thin blood smears. For those patients who may receive quinine or primaquine, a G-6-PD test should be ordered. Lumbar puncture may be indicated in patients who have encephalopathy in which the diagnosis is not clear. Rapid HIV testing may also be indicated in select cases.
- Laboratory diagnosis in the ED may be limited in hospitals that do not have personnel who are well acquainted with malaria or special tests for rapid detection of the disease.
- The British Committee for Standards in Haematology has guidelines on the laboratory diagnosis of malaria.3
Imaging Studies
- A chest radiography may be helpful if respiratory symptoms are present.
- If CNS symptoms are present, a CT scan of the head may be obtained once the patient is stable to evaluate evidence of cerebral edema or hemorrhage.
Other Tests
- Microhematocrit centrifugation
- Using this method with the CBC tube is a more sensitive method of detection of malaria infection.
- However, microhematocrit centrifugation does not allow the identification of the species of Plasmodium. To determine that species, a peripheral blood smear must be examined.
- Giemsa-stained thick and thin peripheral blood smears
- These smears are the criterion standard for malaria detection and should be sent to the laboratory immediately, since malaria is a potentially life-threatening infection.
- When reading the smear, 200-300 oil-immersion fields should be examined (more if the patient recently has taken prophylactic medication, because this temporarily may decrease parasitemia).
- One negative smear does not exclude malaria as a diagnosis; several more smears should be examined over a 36-hour period.
- Fluorescent dyes/ultraviolet indicator tests: Several different dyes allow laboratory results to be obtained more quickly. These methods require the use of a fluorescent microscope (QBC II System, Becton-Dickinson's Quantitative Buffy Coat [QBC] method). Fluorescent /ultraviolet tests may not yield speciation information.
- Polymerase chain reaction
- Polymerase chain reaction (PCR) is a very specific and sensitive test for determining if the species of Plasmodium are present in the blood of an infected individual. PCR is not usually available in most clinical situations.
- PCR is also very effective at detecting the Plasmodium species present in patients with parasitemias as low as 10 parasites/mL of blood.
- Rapid diagnostic tests (RDTs) examples include Para Sight-F test (Becton Dickinson Advanced Diagnostics), ICT Malaria P.f/P.v (Binax Inc), OptiMAL pLDH (DiaMed USA, LLC), Kat-Quick (Katmedical CC), and Rapimal MT Pf Dipstick (Cellabs Pty Ltd) (dipstick tests). Note: This list is not all-inclusive; research individual tests for comparative efficacy and cost.
- These tests are useful in detecting P falciparum infections, while some also may detect other plasmodia antigens. RDTs are based on antibody recognition of the histidine rich protein 2 (HRP-2) antigen of P falciparum and, in most cases, it has been found to be as specific as microscopy studies.4 A false-positive result may occur up to 2 weeks or more after treatment due to persistence of circulating antigens.
- Some RDTs may be able to detect P falciparum in parasitemias that are below the threshold of reliable microscopic species identification.
- RDTs are not as effective when parasite levels are below 100 parasites/mL of blood, and the test rarely is negative in those with high parasitemias. For these reasons, always confirm RDT test results with a second type of screening test when possible.
- RDTs may not be available in the United States due to lack of FDA approval. The World Health Organization's Regional Office for the Western Pacific (WHO/WPRO) provides technical information, including a list of commercially available malaria RDTs, at Malaria Rapid Diagnostic Tests.
- In one study, RDTs were found to perform better than microscopy under routine conditions. RDTs performed by the health facility staff were 91.7% (95% confidence interval [CI], 80.8-100%) sensitive and 96.7% (95% CI, 92.8-100%) specific. Microscopy was 52.5% (95% CI, 33.2-71.9%) sensitive and 77% (95% CI, 67.9-86.2%) specific.5
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References
Centers for Disease Control and Prevention. Malaria. Topic Home. Last updated May 21, 2009. Available at http://www.cdc.gov/malaria/index.htm.
Cox-Singh J, Davis TM, Lee KS, et al. Plasmodium knowlesi malaria in humans is widely distributed and potentially life threatening. Clin Infect Dis. Jan 15 2008;46(2):165-71. [Medline].
[Guideline] Bailey JW, Williams J, Bain BJ, Parker-Williams J, Chiodini P. General Haematology Task Force. Guideline for laboratory diagnosis of malaria. London (UK): British Committee for Standards in Haematology. 2007;19. [Full Text].
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Further Reading
Keywords
malaria, paludism, paludismo, black water fever, blackwater fever, mosquito vector, plasmodia, species, mosquito, mosquito bite
