Diagnostic tests in enzyme allergy.

BACKGROUND

Allergies to enzymes occur frequently in enzyme manufacturing plants. In epidemiologic studies the number of exposed subjects with symptoms is considerably higher than the number of sensitizations as assessed by skin tests or RAST. It was the aim of this study to evaluate the sensitivity and specificity of skin prick tests, enzyme allergosorbent test, and immunoprint with enzymes by using the results of bronchial provocation tests as the "gold standard."

METHODS

We performed 82 bronchial provocation tests with nine different enzymes in 42 chemical plant workers, all of whom had reported work-related symptoms. All tests with the exception of bronchial provocation tests were also performed in 10 atopic and 10 healthy control subjects.

RESULTS

Thirteen workers showed positive results to bronchial provocation tests (50% or greater fall in specific airway conductance) with an enzyme at a maximal concentration of 10 mg/ml. Equivocal test results, that is, tests with a 30% or greater and less than 50% fall in specific airway conductance were seldom. Skin prick tests with nondialyzed aqueous enzyme extracts at a concentration of 10 mg/ml yielded a sensitivity of 100% and a specificity of 93%. Control subjects had no cutaneous reactions to enzymes. Discrepancies between skin tests and bronchial provocation tests occurred in 5 of 82 tests, all with a positive skin test and a negative bronchial provocation test. False-positive skin tests were considered more likely in four subjects and a false-negative bronchial challenge more likely in one case. Enzyme allergosorbent test was 62% sensitive and 96% specific, and atopic control subjects showed positive results in two cases. Results of immunoprint with amylase showed one main band at pH 3.4; this band was also found in exposed subjects without further signs of sensitization, but was not found in control subjects. All but one person with positive results to bronchial provocation tests with enzymes showed bronchial hyperresponsiveness. We identified 13 subjects with bronchial hyperresponsiveness, but without occupational allergy: five of these had sensitizations to nonoccupational allergens and the remainder showed bronchial hyperresponsiveness without any detectable cause.

CONCLUSIONS

Occupation-related symptoms were not indicative of occupational allergy. Bronchial provocation tests and skin prick tests with nondialyzed aqueous enzyme extracts were appropriate techniques for the diagnosis of enzyme allergy.