[Is the severity of occupational asthma related to the molecular weight of the allergen?]. / La sévérité de l'asthme professionnel est-elle liée au poids moléculaire de l'allergène?

INTRODUCTION: The aim of the study was to compare the characteristics of occupational asthma (OA) resulting from sensitisation to allergens of high (HMW) or low (LMW) molecular weight. METHODS: All new cases of allergic OA seen in an occupational health department between January 2001 and March 2004 were included. The patients underwent a standardised assessment including a questionnaire, skin tests, spirometry and measurement of non-specific bronchial reactivity. They were divided into 2 groups depending on the molecular weight of the causal agent (groups HMW and LMW). RESULTS: 77 patients were included, 30 in the HMW group and 47 in the LMW group. No significant difference in severity at the time of diagnosis was found between the two groups (symptoms, spirometry, PD20 methacholine) but the time between the first symptoms and diagnosis was longer in the HMW group (7.1 +/- 7.8 years against 3.2 +/- 4.1 years, p = 0.01). Atopy was more common in the HMW group (57% vs. 27%, p = 0.01). CONCLUSION: The severity of OA at the time of diagnosis does not appear to be influenced by the molecular weight of the causal agent.

Gastro-oesophageal reflux prevalence and relationship with bronchial reactivity in asthma.

The relationship between asthma and gastro-oesophageal reflux (GER) is controversial. In an allergy department, GER prevalence was evaluated in asthmatics, with a view to judging the potential influence of GER on asthma. One hundred and five asthmatics were recruited and co-investigated for GER and lung function. Descriptive analysis was performed, patients with (GER+) and without (GER-) GER were then compared, and finally, stepwise regression analysis was used. GER prevalence was 32%. Lung parameters did not differ between GER+ and GER- patients. When restricting analysis to GER+ patients, bronchial reactivity was closely correlated to the number of reflux episodes (NRE) (r=0.983; p=0.001). When comparing patients with more than 15 reflux episodes x day(-1) (n=50), with those having less (n=43), no differences were found in lung function and GER parameters. However, there was a positive correlation between the provocative dose of methacholine causing forced expiration volume to fall 20% from the baseline and NRE in patients with NRE>15 (r=0.561; p=0.05). In conclusion, gastro-oesophageal reflux was observed in a third of the asthma patients studied. These data do not support a firm aetiological relationship between gastro-oesophageal reflux and asthma, but do suggest an association between the number of reflux episodes and bronchial hyperresponsiveness.