Weil-Felix test is based on cross-reactions which occur between antibodies produced in acute rickettsial infections with antigens of OX (OX 19, OX 2, and OXK) strains of Proteus species. Dilution of patient’s serum are tested against suspensions of the different Proteus strains.

Weil-Felix reaction is a test used to diagnose rickettsial infections.

Negative test: Antibody titer ≤ 1:80 (varies between laboratories).

Positive test: A titer of ≥1:160 is considered suggestive of rickettsial infection, but confirmation is needed with additional tests.

Interpretation of Results:

• Positive result: A significant rise in antibody titers (fourfold increase) between acute and convalescent samples suggests a rickettsial infection.
• False positives: Can occur in typhoid fever, leptospirosis, tuberculosis, brucellosis, viral infections, or autoimmune diseases.
• False negatives: May occur in early infection stages when antibodies are not yet detectable.

Blood