Incidence of work-related symptoms in relation to the time of occurrence of skin reactivity to laboratory animal-derived antigens
| Skin reactivity | PPV | |||||
| Present | Absent | |||||
| Before symptoms | Same time as symptoms | After symptoms | No symptoms | |||
| Cutaneous symptoms | 21 | 22 | 7 | 67 | 31 | 32/117 28 (19–35) |
| Work-related RC symptoms | ||||||
| Nasal | 18 | 17 | 13 | 42 | 44 | 27/90 30 (21–41) |
| Ocular | 14 | 16 | 17 | 59 | 31 | 22/106 21 (14–30) |
| Nasal and/or ocular | 17 | 19 | 17 | 26 | 46 | 27/90 30 (21–41) |
| Work-related respiratory symptoms | ||||||
| Dyspnoea | 7 | 1 | 5 | 110 | 8 | 8/123 6.5 (3–13) |
| Wheezing | 8 | 4 | 6 | 111 | 3 | 10/129 8.0 (4–14) |
| Dyspnoea and/or wheezing | 9 | 4 | 6 | 103 | 3 | 11/22 9.0 (5–16) |
Data are presented as n except for positive predictive values (PPV) which show incidence calculated as described below as % (95% confidence interval (CI))
The numerator is the total of (all incident cases of symptoms detected after the occurrence of skin reactivity)+(half of incident cases of symptoms detected at the same time as skin reactivity) (see text for rationale)
the denominator is the number of subjects with skin reactivity at baseline or at follow-up and without the pertinent symptom at baseline
CI values are computed under the naive assumption that PPV is a simple proportion