Occupational asthma in symptomatic workers exposed to natural rubber latex: Evaluation of diagnostic procedures

Abstract

Background: Natural rubber latex (NRL) has been increasingly identified as a cause of occupational asthma (OA). Objective: We sought to examine the accuracy of the clinical history, immunologic tests, and assessment of nonspecific bronchial hyperresponsiveness in diagnosing OA caused by latex compared with that of the specific inhalation challenge (SIC). Methods: Forty-five consecutive patients referred for investigation of possible OA caused by latex underwent a diagnostic protocol, including an open medical questionnaire, skin prick testing against latex, measurement of bronchial responsiveness to histamine, and inhalation challenge with latex gloves. Recorded clinical history was judged retrospectively by 4 physicians who were blinded for the results of other objective tests. Results: The clinical history, skin prick testing against NRL, and assessment of nonspecific bronchial hyperresponsiveness showed a high sensitivity (87%, 100%, and 90%, respectively) but a low specificity (14%, 21%, and 7%, respectively) when compared with the results of the SIC. Logistic regression analysis showed that combining the results of skin prick tests against latex with the clinical history enhanced the negative predictive value from 50% to 71%, whereas the positive predictive value remained virtually unchanged (75 % vs 76 %). Conclusion: The clinical history and immunologic tests were the most useful procedures in diagnosing NRL-induced asthma, although combining the 2 procedures remained less accurate than SIC. Further examination of the predictive values of available tests is warranted to recommend diagnostic strategies that are specific to the various agents causing OA.