Flowchart illustrating the idealised laboratory diagnosis of acute Q fever infection
Return to the
NSW Control Guideline for public health units for Q fever.
Diagnosis
Acute, clinically compatible illness
- PCR test:
- Detected
- Notification and public health follow-up
- Confirmed case
-
Not detected
-
Send for initial (acute) serology
-
Initial (acute) serology:
-
Ab1 detected
-
Notification and public health follow-up
-
Possible case
-
Obtain follow-up (convalescent) sera 2-3 weeks after initial specimens
-
Ab1 not detected
-
Obtain follow-up (convalescent) sera 2-3 weeks after initial specimens
-
Paired sera testing (after obtaining convalescent sera 2-3 weeks after initial specimens)
- Ab1 detected (seroconversion) or 4-fold rise in titre
- Confirmed case (updated from possible)
-
Ab1 not detected or <4-fold rise in titre2
References
-
Serological patterns and the detection of Q fever-specific antibody (Ab) is dependent on the time from onset of illness, assay completed (i.e. IFA, CFT, EIA) and past exposure to the organism. Refer to
section 7 and
Appendix 5 of the NSW Control Guidelines for detail.
-
Significant antibody titres may take 3-4 weeks from illness onset to appear in some cases. In cases not definitively confirmed by other means, a third sample is recommended, which should be collected 3-4 weeks after fever onset.