The diagnostic value of routine spirometry in occupational health practice for early detection of silicosis: a retrospective Belgian study among silica-exposed workers

Objective Silicosis is a pneumoconiosis caused by respirable crystalline silica (RCS). As current surveillance methods have low sensitivity for early detection we evaluated the value of pre-diagnostic occupational spirometry monitoring. Methods To investigate the possibility of detecting disease we assessed 58 RCS-exposed cases by linking lung function abnormalities to CT readings. Univariate, stepwise logistic regression and ROC analysis were performed. Results Of 31 workers with RCS-related CT abnormalities, 25 were classified as silicosis. Fixed cut-off predicted values (FCO) for FEV1 and FVC of < 80% and FEV1/FVC of < 0.7, FEV1% predicted decline > 15%, and FEV1 decline > 60 mL/year were significantly associated with pathological outcome. Combining FCO (p = 0.001) and percentage predicted method (PPM) (p = 0.023) best predicted silicosis (AUCROC = 0.84). Conclusions To identify RCS-exposed workers requiring diagnostic referral priority should be given to those with FCO, PPM and annual FEV1 decline abnormalities.