Table 3. Course of IgG phase I and phase II antibody titers (increase, constant, decrease) in veterinarians (n = 76) and Q fever patients (n = 98) in two samples taken in a three-year time period.a .
| Course | IgG phase I titer | IgG phase II titer | |||
|---|---|---|---|---|---|
| Veterinarians (n = 76) | Patients (n = 98) | Veterinarians (n = 76) | Patients (n = 98) | ||
| n (%) | n (%) | n (%) | n (%) | ||
| Increase | Total increase | 28 (36.8) | 6 (6.1) | 23 (30.3) | 6 (6.1) |
| 2-fold | 21 (27.6) | 4 (4.1) | 17 (22.4) | 4 (4.1) | |
| 4-fold | 7 (9.2) | 0 (0.0) | 6 (7.9) | 0 (0.0) | |
| 8-fold | 0 (0.0) | 1 (1.0) | 0 (0.0) | 0 (0.0) | |
| ≥16-fold | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | |
| Undeterminedb | 0 (0.0) | 1 (1.0) | 0 (0.0) | 2 (2.0) | |
| Constant | 23 (30.3) | 10 (10.2) | 30 (39.5) | 16 (16.3) | |
| Decrease | Total decrease | 24 (31.6) | 82 (83.7) | 23 (30.2) | 75 (76.5) |
| 2-fold | 18 (23.7) | 17 (17.3) | 19 (25.0) | 27 (27.6) | |
| 4-fold | 5 (6.6) | 29 (29.6) | 2 (2.6) | 17 (17.3) | |
| 8-fold | 1 (1.3) | 12 (12.2) | 1 (1.3) | 10 (10.2) | |
| ≥16-fold | 0 (0.0) | 24 (24.5) | 0 (0.0) | 7 (7.1) | |
| Undeterminedb | 0 (0.0) | 0 (0.0) | 1 (1.3) | 14 (14.3) | |
| No end titration, not specifiedb | 1 (1.3) | 0 (0.0) | 0 (0.0) | 1 (1.0) | |
a First serum sample: veterinarians in 2009 or 2010; patients in 2008 or 2009 (twelve months after acute Q fever diagnosis in 2007 or 2008). Follow-up sample: veterinarians in 2013 (three to four years after first sample); patients in 2011 or 2012 (four years after acute Q fever diagnosis in 2007 or 2008).
b Because some samples did not have and end titration (e.g., >1:4,096), the number of decreased dilutions could not be established.