Natural history of sensitization, symptoms and occupational diseases in apprentices exposed to laboratory animals

Table 1—

Time-course of work-related symptoms and occupational diseases in apprentices exposed to laboratory animals

Data presented as n (%) or incidence (%)
Total number of participants=417 except for the assessment of occupational asthma (n=373) because 44 students refused the methacholine inhalation test
number of cases/person-yrs in the programme

Table 2—

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	Absent
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