Table 5.
Serological follow-up of cases and controls
| Possible chronic Q fever | Possible chronic Q fever | ||||
|---|---|---|---|---|---|
| Antibody titers on the 24 thmonth after acute Q fever diagnosis | IgG phase I | IgG phase II | Antibody titers on the 36 thmonth after acute Q fever diagnosis | IgG phase I | IgG phase II |
| <1:32 | 0 (0.0%) | 0 (0.0%) | <1:32 | 0 (0.0%) | 0 (0.0%) |
| 1:32 - 1:128 | 2 (7.4%) | 0 (0.0%) | 1:32 - 1:128 | 1 (4.8%) | 0 (0.0%) |
| 1:256 - 1:512 | 7 (25.9%) | 2 (7.4%) | 1:256 - 1:512 | 7 (33.3%) | 3 (14.3%) |
| 1:1,024 - 1:2,048 | 12 (44.4%) | 13 (48.1%) | 1:1,024 - 1:2,048 | 10 (47.6%) | 12 (57.1%) |
| ≥1:4,096 | 6 (22.2%) | 12 (44.4%) | ≥1:4,096 | 3 (14.3%) | 6 (28.6%) |
| IgG phase I | IgG phase II | ||||
| Antibody titers on the 48 th month after acute Q fever diagnosis | Possible chronic Q fever | No chronic Q fever † | Antibody titers on the 48 th month after acute Q fever diagnosis | Possible chronic Q fever | No chronic Q fever † |
| <1:32 | 1 (2.9%) | 55 (51.0%) | <1:32 | 0 (0.0%) | 3 (2.8%) |
| 1:32 - 1:128 | 6 (17.6%) | 47 (43.9%) | 1:32 - 1:128 | 0 (0.0%) | 31 (29.0%) |
| 1:256 - 1:512 | 11 (32.4%) | 5 (4.7%) | 1:256 - 1:512 | 5 (14.7%) | 51 (47.7%) |
| 1:1,024 - 1:2,048 | 10 (29.4%) | 0 (0.0%) | 1:1,024 - 1:2,048 | 19 (55.9%) | 19 (17.8%) |
| ≥1:4,096 | 6 (17.6%) | 0 (0.0%) | ≥1:4,096 | 10 (29.4%) | 3 (2.8%) |
| p-value =0.001* | p-value =0.001* | ||||
*Chi-square test is used to calculate the p-value.
†There were three patients without chronic Q fever of which serological data of four years after acute Q fever diagnosis was missing.