Table 1. Laboratory case definition of acute Q fever patients included in the study (n = 183).
| No. | Laboratory definition | n (%) |
| 1 | PCR positive and an IgG phase II and/or IgG phase I seroconversion with at least IgG phase II≥1∶64 in follow-up | 46 (25.1) |
| 2 | IgG phase II and/or phase I seroconversion with at least IgG phase II≥1∶64 in follow-up | 59 (32.2) |
| 3 | IgG phase II and/or IgG phase I fourfold increase in antibody titre with at least IgG phase II≥1∶64 in follow-up | 9 (4.9) |
| 4 | IgM phase II “positive” (untitrated)a or ≥1∶64 and IgG phase II “positive” (untitrated) or ≥1∶64 at diagnosis, and IgG phase II≥1∶64 in follow-up (when available)b | 69 (37.7) |
No.: number.
a
Due to the large number of samples that were submitted to our laboratory for Q fever diagnostics (over 18,000 samples in 2009), IFA was sometimes not titrated, but only recorded as “positive”.
b
At least one follow-up sample was available for 177/183 (96.7%) patients.