Quantitative bronchial challenge tests with wheat flour dust administered by Spinhaler: Comparison with aqueous wheat flour extract inhalation☆☆☆★★★

Abstract 

Background: Quantitative bronchial challenge tests with flour dust for the diagnosis of bakers' asthma may be performed by inhalation of flour delivered to the patient's respiratory tract by sophisticated equipment. Objective: This study was carried out to assess the diagnostic value of bronchial challenge tests with flour dust inhalation from capsules administered by a Spinhaler (Fisons Inc., Loughborough, U.K.) and to compare this method quantitatively with bronchial challenge tests with a commercially available wheat flour extract. Methods: A highly selected group of 36 bakers with work-related symptoms of rhinitis or asthma were referred to our department, a tertiary referral center, from 1992 to 1995. Thirty-four of the subjects and 10 atopic control subjects were included in this study. After the assessment of bronchial hyperresponsiveness on day 1, subjects were randomized to inhale an aqueous wheat flour extract at concentrations of 0.01, 0.1, 1, 10, and 100 mg/ml by tidal volume breathing for 10 minutes or to inhale wheat flour dust filled in capsules on days 2 and 3. One, two, and four capsules (maximum of 7 cumulative capsules) of flour dust were administered by a Spinhaler. In addition, skin prick tests were performed with a battery of environmental and occupational allergens. Total serum IgE and specific IgE to wheat flour were measured by standard procedures. Results: Seventeen bakers and two control subjects demonstrated a positive skin test response to wheat flour (wheal ≥3 mm). Fifteen bakers demonstrated a fall of 50% or more in specific airway conductance after inhalation of the commercial wheat flour extract, and 11 demonstrated such a fall in specific airway conductance after inhalation of wheat dust. Three control subjects had a positive bronchial challenge response to the extract, but dust inhalation from the capsule did not cause positive bronchial reactions in control subjects. When a 50% fall of specific airway conductance was used as criterion for a positive bronchial provocation test result, sensitivity for the extract or dust inhalation was 0.44 and 0.32, respectively, and specificity was 0.7 and 1.0, respectively. If only subjects with a positive skin test response to wheat flour were considered, sensitivity of both tests was 0.65. With more stringent criteria for the gold standard, there was a trend for a higher sensitivity but a lower specificity of the extract inhalation. Both methods were safe. Conclusion: The validity of bronchial challenge tests with wheat flour dust inhaled from Spinhaler capsules was superior to that of tests done with a commercially available aqueous wheat flour extract. The higher specificity of the Spinhaler method might be an advantage if bronchial challenge tests are used as confirmation tests. (J Allergy Clin Immunol 1997;100:199-207.)

Keywords:  Bakers' asthma, wheat flour, bronchial challenge, occupational asthma, diagnosis

Abbreviations:  PD₅₀sGaw , Provocative dose causing a 50% fall in specific airway conductance, ROC , Receiver-operating characteristic, SPT , Skin prick test