Work-exacerbated asthma and occupational asthma: do they really differ?

BACKGROUND: Although work-exacerbated asthma (WEA) is a prevalent condition likely to have an important societal burden, there are limited data on this condition. OBJECTIVES: The aims of this study were (1) to compare the clinical, functional, and inflammatory characteristics of workers with WEA and occupational asthma (OA) and (2) compare health care use and related costs between workers with WEA and OA, as well as between workers with work-related asthma (WRA; ie, WEA plus OA) and those with non-work-related asthma (NWRA) in a prospective study. METHODS: We performed a prospective observational study of workers with and without WRA with a 2-year follow-up. The diagnosis of OA and WEA was based on the positivity and negativity of results on specific inhalation challenges, respectively. RESULTS: One hundred fifty-four subjects were enrolled: 53 with WEA, 68 with OA, and 33 control asthmatic subjects (NWRA). WEA was associated with more frequent prescriptions of inhaled corticosteroids (odds ratio [OR], 4.4; 95% CI, 1.4-13.6; P = .009), a noneosinophilic phenotype (OR, 0.3; 95% CI, 0.1-0.9; P = .04), a trend toward a lower FEV1 (OR, 0.9; 95% CI, 0.9-1.0; P = .06), and a higher proportion of smokers (OR, 2.5; 95% CI, 0.96-9.7; P = .06) than the diagnosis of OA. The health care use of WRA and related costs were 10-fold higher than those of NWRA. CONCLUSION: Workers with WEA appeared to have features of greater asthma severity than workers with OA. In contrast with OA, WEA was associated with a noneosinophilic phenotype. Both OA and WEA were associated with greater health care use and 10-fold higher direct costs than NWRA.

Frequency of work-related respiratory symptoms in workers without asthma.

BACKGROUND: Clinicians are faced with subjects complaining of work-related respiratory symptoms (WRS) without any evidence of asthma. We sought to assess the prevalence of subjects with WRS without asthma in a cohort of workers referred for possible work-related asthma (WRA) as well as compare the characteristics and the work environment of subjects with WRS to subjects with WRA. METHODS: A prospective observational study of workers referred for possible WRA over a 1-year period. Detailed medical and occupational questionnaires were administered. Pulmonary function tests as well as specific-inhalation challenges were performed. RESULTS: One hundred twenty workers were investigated. Fifty-one had WRA while 69 had WRS. The type and the severity of the respiratory symptoms were similar in both groups, except for wheezing which was more frequently reported in subjects with WRA (32 (62.7%)) than in subjects with WRS (16 (23.2%)) (P < 0.01). Both the workers with WRS and WRA were mainly employed in the manufacturing sector (64.7% (WRA) and 71% (WRS)). At the time of the first assessment 64.7% of subjects with WRA and 56.5% with WRS had left their workplace because of their bothersome respiratory symptoms. CONCLUSIONS: Subjects with WRS without asthma represent a large proportion of the subjects assessed in clinics specialized in the field of WRA. Like subjects with WRA, the population with WRS is likely to represent a significant medical burden. The similarity of the symptoms between the WRA and the WRS groups emphasizes the need to perform a thorough and objective investigation to diagnose WRA.

Comparison of peak expiratory flow variability between workers with work-exacerbated asthma and occupational asthma.

BACKGROUND: Peak expiratory flow (PEF) monitoring is frequently used to diagnose occupational asthma (OA). The variability of PEF between periods at work and away from work has not been described in workers with work-exacerbated asthma (WEA). We sought to assess and compare the diurnal variability of PEF during periods at and away from work between subjects with OA and WEA. METHODS: Workers referred for work-related asthma underwent PEF monitoring for 2 weeks at and away from work. The diagnostic of OA or WEA was subsequently made according to the respective positivity or negativity of the specific inhalation challenges. PEF mean diurnal variability was calculated during periods at and away from work. PEF graphs were also interpreted using direct visual analysis by five observers and using a computer program (Oasys-2, Expert System ) [available at: http://www.occupationalasthma.com]. RESULTS: Thirty-four subjects were investigated (WEA, n = 15; OA, n = 19). There was a greater variability of PEF at work than away from work in both OA (19.8 +/- 8.7% vs 10.7 +/- 6.3%, p < 0.001) and WEA (14.2 +/- 4.8% vs 10.6 +/- 5.6%, p = 0.02). However, the magnitude of the variability was higher in OA than in WEA (p = 0.02). The visual interpretation of PEF or the Oasys-2 program failed to distinguish WEA from OA. CONCLUSION: Although workers with OA showed a higher PEF variability than workers with WEA when at work, clinicians were unable to reliably differentiate OA from WEA using the visual interpretation of PEF graphs or the computerized analysis.

Investigation of occupational asthma: sputum cell counts or exhaled nitric oxide?

BACKGROUND: The measure of sputum eosinophil counts is a useful tool in the investigation of occupational asthma (OA), but processing sputum is time consuming. Measuring the fractional concentration of exhaled nitric oxide (FENO) may be an alternative in clinical practice. The aim of this study was to assess the respective changes of sputum eosinophil counts and FENO following exposure to occupational agents in the routine practice of two tertiary centers in North America and Europe. METHODS: Workers undergoing specific inhalation challenges (SICs) for possible OA in tertiary clinics in both Canada and Belgium were enrolled. Sputum cell counts and FENO were collected at the end of the control day and at 7 and 24 h after exposure to the offending agent. RESULTS: Forty-one subjects had a negative SIC; 26 subjects had OA proven by a positive SIC. In subjects with positive SIC, there was a significant increase in sputum eosinophils at 7 h (9.0 [9.9]%) and 24 h (11.9 [14.9]%) after exposure compared with the baseline (2.8 [4.2]%), whereas there was a significant increase in FENO only 24 h after exposure (26.0 [30.5] ppb) compared with the baseline (16.6 [18.5] ppb). A 2.2% change in sputum eosinophil counts achieved a much higher sensitivity and positive predictive value than a 10-ppb change in FENO with similar specificity and negative predictive value for predicting a 20% decrease in FEV(1) during SICs. CONCLUSIONS: Sputum eosinophil counts constitute a more reliable tool than FENO to discriminate positive and negative SICs.