WEIL- FELIX TEST, SERUM

      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

• Aid in the diagnosis of rickettsial infections when more specific tests (e.g., IFA, ELISA) are unavailable

• Provide epidemiological support in resource-limited settings

• Support clinical suspicion in patients with fever and rash in endemic areas

Symptoms That May Lead to the Test

• High fever with chills

• Severe headache

• Rash (spotted or maculopapular)

• Enlarged lymph nodes

• History of exposure to lice, fleas, ticks, or mites

• Travel or residence in rickettsia-endemic areas

Abnormal Results

• Positive test (agglutination with Proteus antigens):

  • Suggests possible rickettsial infection (type may vary with antigen involved):

    • OX19: Typhus group

    • OX2: Spotted fever group

    • OXK: Scrub typhus

  • More reliable if there is a fourfold rise in titer on paired samples

• False positives:

  • Can occur with unrelated infections or prior exposure

  • Cross-reactivity limits specificity

• Negative test:

  • Does not rule out rickettsial infection (low sensitivity in early stages)

Risks

• Minimal, limited to standard blood draw risks (mild pain, bruising, or dizziness).