WHAT IT IS ?
The Weil-Felix test is a serological agglutination test performed on serum. It detects antibodies against Proteus species (OX2, OX19, OXK antigens), which cross-react with rickettsial antigens. It is an older, non-specific test used to help diagnose rickettsial infections (e.g., typhus, spotted fever, scrub typhus).
Uses
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Aid in the diagnosis of rickettsial infections when more specific tests (e.g., IFA, ELISA) are unavailable
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Provide epidemiological support in resource-limited settings
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Support clinical suspicion in patients with fever and rash in endemic areas
Symptoms That May Lead to the Test
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High fever with chills
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Severe headache
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Rash (spotted or maculopapular)
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Enlarged lymph nodes
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History of exposure to lice, fleas, ticks, or mites
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Travel or residence in rickettsia-endemic areas
Abnormal Results
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Positive test (agglutination with Proteus antigens):
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Suggests possible rickettsial infection (type may vary with antigen involved):
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OX19: Typhus group
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OX2: Spotted fever group
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OXK: Scrub typhus
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More reliable if there is a fourfold rise in titer on paired samples
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False positives:
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Can occur with unrelated infections or prior exposure
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Cross-reactivity limits specificity
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Negative test:
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Does not rule out rickettsial infection (low sensitivity in early stages)
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Risks
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Minimal, limited to standard blood draw risks (mild pain, bruising, or dizziness).



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