QUANTITATIVE BRONCHIAL CHALLENGE TESTS WITH WHEAT-FLOUR DUST ADMINISTERED BY SPINHALER - COMPARISON WITH AQUEOUS WHEAT-FLOUR EXTRACT INHALATION

Background: quantitative bronchial challenge tests with flour dust for the diagnosis of bakers' asthma may be performed by inhalation of flo ur delivered to the patient's respiratory tract by sophisticated equip ment. Objective: This study was carried out to assess the diagnostic v alue of bronchial challenge tests with hour dust inhalation from capsu les administered by a Spinhaler (Fisons Inc., Loughborough, U.K.) and to compare this method quantitatively with bronchial challenge tests w ith a commercially available wheat Flour extract. Methods: A highly se lected group of 36 bakers with work-related symptoms of rhinitis or as thma were referred to our department, a tertiary referral center, from 1992 to 1995. Thirty-four of the subjects and 10 atopic control subje cts were included in this study, After the assessment of bronchial hyp erresponsiveness on day 1, subjects were randomized to inhale an aqueo us 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 flou r 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 batt ery of environmental and occupational allergens, Total serum IgE and s pecific IgE to wheat hour were measured by standard pocedures. Results : Seventeen bakers and two control subjects demonstrated a positive sk in test response to wheat hour (wheal greater than or equal to 3 mm), Fifteen bakers demonstrated a fall of 50% or more in specific airway c onductance after inhalation of the commercial wheat hour extract, and II demonstrated such a fall in specific airway conductance after inhal ation of wheat dust. Three control subjects had a positive bronchial c hallenge 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 extrac t 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 t est response to wheat flour were considered, sensitivity of both tests was 0.65. With more stringent criteria for the gold standard, there w as a trend for a higher sensitivity but a lower specificity of the ext ract inhalation, Both methods were safe. Conclusion: The validity of b ronchial challenge tests with wheat hour dust inhaled from Spinhaler c apsules was superior to that of tests done with a commercially availab le aqueous wheat hour extract, The higher specificity of the Spinhaler method might be an advantage if bronchial challenge tests are used as confirmation tests.