Yates’ corrected values were used in x2 analyses, and Mantel-Haenzel method and Fisher’s Exact Test were used to test and to explore associations. Odds ratios and the Cornfield 95% confidence limit for the odds ratios were calculated. Relative risks with Taylor series 95% confidence limits for relative risk were estimated and Student’s t tests compared group differences.
The final study population consisted of 86 subjects. The group demographics, atopic/allergic status, FEV1%, and provocative concentration causing a 20% fall in FEVX (PC20) values are summarized in Table 1. Of 86 asthmatic subjects, 54 (63%) suffered asthma from an irritant exposure while 11 (13%) were diagnosed as having asthma caused by a sensitizer. There were 21 subjects (24%) determined not to suffer occupational/environmental exposure-related asthma. There was excellent consistency of the diagnoses made by the three different investigators; a discordance usually centered on whether there was sufficient information to include a subject in the final study population. No case was excluded because of a disagreement with the diagnosis.
The age distribution of the 86 subjects ranged between 17 and 71 years; there were 40 men and 46 women. Forty-six of the 86 (53%) were current or former cigarette smokers. Most nonsmokers appeared among the irritant-induced asthma group (73% of total). Subjects with asthma caused by an allergic sensitizer exhibited lower lung function values. The 16 subjects presumed to have new-onset irritant-induced asthma but who were suffering from an exacerbation of preexisting asthma in remission showed higher results of lung function tests than the 38 new-onset asthma patients; findings of both of the latter two groups were statistically significantly different as shown in Table 1. There were no statistically significant differences in PC20 values among the four groups (Table 1).
Types of Irritant-Induced Asthma
Two clinical presentations were appreciated. Among the 54 persons with irritant-induced asthma, 38 (70%) were specified as having new-onset irritant-induced asthma; a preexisting asthmatic disorder, occurring before the exposure event, could not be substantiated for this group.
Table 1—Demographics of Study Population
|Age, yr, mean±SE||Sex||Smoking||Atopy, No. (%)||FEV,%,(±SE)||PC2mg/mL,mean±SE|
|Allergicoccupational Irritant induced||11||43.4 ±2.3||7||4||6||5||1||71.2 (6.8)||2.4±1.0|
|New onset||38||39.2±1.7||17||21||20||18||25||80.3 (3.1)||3.1±0.7|
|Not occupational/ environmental exposed||21||41.2±2.9||11||10||15||6||8||81.0 (4.2)||2.0±0.5|