Table 2—

Incidence of work-related symptoms in relation to the time of occurrence of skin reactivity to laboratory animal-derived antigens

Skin reactivityPPV
Before symptomsSame time as symptomsAfter symptomsNo symptoms
Cutaneous symptoms21227673132/117 28 (19–35)
Work-related RC symptoms
 Nasal181713424427/90 30 (21–41)
 Ocular141617593122/106 21 (14–30)
 Nasal and/or ocular171917264627/90 30 (21–41)
Work-related respiratory symptoms
 Dyspnoea71511088/123 6.5 (3–13)
 Wheezing846111310/129 8.0 (4–14)
 Dyspnoea and/or wheezing946103311/22 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