The three patients who met the criteria for having probable occupational asthma worked in different industries. The industry with the largest percentage of patients with probable or possible occupational asthma was the manufacturing of transportation equipment, which includes the automobile parts industry.
From this study, if patients were classified only on the basis of whether they attribute the cause of their asthma to work exposure, the percentage of patients with occupational asthma would be 25.5 percent. This compares with the result of 15 percent in a national study that asked the same question. Of the patients who self-reported an association with work, only 11 (45.8 percent) met the criteria outlined in this study for having probable or possible occupational asthma. Conversely, 55 percent of the patients we classified as having probable or possible occupational asthma did not attribute their asthma to work exposure. Given the absence of confirmatory testing for occupational asthma, one cannot actually determine if the selfreported percentage of 25.5 percent of patients who thought their asthma was caused by poor working conditions is a more accurate percentage than the percentage obtained by using the NIOSH criteria. my canadian pharmacy online
The study had a number of limitations. The first limitation was that the primary hospital discharge diagnosis of asthma was not standardized. No attempt was made to determine the criteria used by individual physicians to make the diagnosis of asthma. We accepted the hospital discharge diagnosis to be adequate to meet criterion A. The fact that 12.9 percent of the patients reported having emphysema highlights our concern about the criteria used by physicians to diagnose asthma. Other limitations included the small sample size, the response rate (46.5 percent), and the selection of patients from only three hospitals. Although the response rate was low, there was no difference in gender and age between the responders and nonresponders. We adjusted for the difference in response by hospital. If we assumed that none of the patients who were not interviewed had probable or possible occupational asthma, then our estimated prevalence rate would be 9.9 percent. This rate is still higher than some national estimates. Finally, definitive tests were not performed to confirm the diagnosis of occupational asthma. None of the three probable occupational asthma cases was confirmed and there could be alternative explanations for their symptoms. Formaldehyde sensitivity occurs in a minority of patients with symptoms from exposure to formaldehyde. There is limited evidence of oil mist sensitivity and the firefighter who by history had RADS was a smoker whose symptoms increased over time.
Further studies with a larger sample size and a wider selection of patients from other hospitals are necessary to determine an exact estimate of the prevalence of occupational asthma. Additional tests, such as the use of peak flow meters, are needed to confirm the questionnaire data on the relationship between symptoms and work exposure. Actual characterization of the work exposure should also be included in these future studies.