A preliminary comparison of five assays for detecting past exposure to <em>Coxiella burnetii</em> for use prior to human Q fever vaccination — ASN Events
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  3. A preliminary comparison of five assays for detecting past exposure to Coxiella burnetii for use prior to human Q fever vaccination

A preliminary comparison of five assays for detecting past exposure to Coxiella burnetii for use prior to human Q fever vaccination (#240)

Stephen R. Graves 1 , Paul Ross 2 , Chelsea Nguyen 3 , Meg Jeppesen 2 , John Stenos 3 , Jenny Robson 2
  1. Australian Rickettsial Reference Laboratory, New Lambton, NSW, Australia
  2. Sullivan Nicolaides Pathology (SNP), Brisbane
  3. Australian Rickettsial Reference Laboratory, Geelong, VIC, Australia

Background

Vaccination against Q Fever (Coxiella burnetii infection) is performed in Australia using Q-VAX, a formalin-killed whole cell vaccine. Adverse reactions occur in those persons with prior exposure to C.burnetii. To prevent this adverse reaction pre-vaccination screening is performed and persons found to be positive are excluded from vaccination. Currently a skin test (to detect T-cell immunity) and an antibody assay (to detect B-cell immunity) are undertaken on each person prior to vaccination. However the assay that "best" correlates with prior exposure to C.burnetii and thus adverse reactions to the vaccine is not known.

A new interferon-gamma release assay (IGRS), "Q-Detect", has recently become available. This new assay and 4 current assays were compared.

 

Material/Methods

A small group (n=25) of attendees at an Australian scientific conference were offered Q-VAX vaccination. As part of their pre-vaccination testing, 5 different assays were performed on them to detect their possible prior exposure to C.burnetii. The assays were:

  1. intradermal skin test inoculation
  2. serology by immunofluorescence (IF)
  3. serology by enzyme immunoassay (EIA)
  4. serology by complement fixation test (CFT)
  5. IGRA ( the new assay)

Results

Of the 25 participants in the study, 7 had prior exposure to C.burnetii due to vaccination against Q Fever and 1 had prior Q Fever infection. The remaining 17 persons had no known prior exposure to C.burnetii.

The results from the 5 assays were compared in the 2 groups and the sensitivity and specificity of the assays calculated, as under:

  Assay                              Sensitivity            Specificity    Conclusion   

 1 skin test                          37%                     76%             Poor

 2 serology IF                       62%                   100%             Poor

 3 serology EIA                     25%                   100%             Poor

 4 serology CFT                     12%                   100%             Poor

 5 IGRA                              100%                     82%            Good

Conclusion

The new IGRA "Q-Detect" is superior to the 4 currently used assays for detecting prior exposure to C.burnetii in persons seeking vaccination against Q Fever in Australia.

#2018ASM