A comparison between Venables standardized respiratory questionnaire and pre-shift spirometry in screening of occupational asthma in a steel industry.

BACKGROUND Occupational asthma (OA) is the most common occupational lung disease in developed countries. One of the causative agents is metal fume that may be encountered in steel industries. Screening for the OA is mainly performed by questionnaire but in our country spirometry is used more commonly. OBJECTIVE To compare the diagnostic value of the Venables standardized respiratory questionnaire and pre-shift spirometry as screening tools for OA. METHODS In a cross-sectional study, we investigated 450 workers of a steel industry by the Venables standardized questionnaire. We also performed a pre-shift spirometry as the screening spirometry and a post-shift spirometry. A person with 10% drop in post-shift FEV1 compared with the pre-shift value was considered as asthmatic (our gold-standard). The results of the questionnaire and the pre-shift spirometry were then examined against the gold-standard test results. For each test, sensitivity, specificity, positive and negative predictive values were calculated. RESULTS The overall prevalence of OA among our studied workers was 3.9% (95% CI: 1.9%-5.9%). The highest rate was seen in those working in catering (25%) and welding (10%) units. Pre-shift spirometry and the questionnaire had low sensitivity (42.9% and 28.6%, respectively) and positive predictive values (16.7% and 3.6%, respectively); moderate specificity (92.4% and 71.6%, respectively) and high negative predictive values (97.9% and 96.5%, respectively). CONCLUSION Taking into account the ease of use of the questionnaire, it seems that it is more feasible to use questionnaire as the primary screening tool for the diagnosis of OA.