Weil-Felix is a nonspecific agglutination test which detects anti-rickettsial antibodies in patient’s serum based on cross-reactions with antigens of OX (OX 19, OX 2, and OXK) strains of Proteus species.
The Weil–Felix test has an overall sensitivity of 33% and specificity of 46%. So, it has largely been replaced by other methods of serology, including indirect immunofluorescence antibody (IFA) testing, which is the gold standard or the PCR test.
However, in resource-limited settings, it still remains an important tool in the diagnosis.
Results of a Weil Felix are interpreted as follows-
|Typhus group rickettsiae||OX19|
|Spotted fever group rickettsiae||OX2 & OX19|