The success and safety profile of sputum induction in patients with chronic obstructive pulmonary disease: An Indian experience.

Background: Neutrophilic inflammation is common in chronic obstructive pulmonary disease while Asthma COPD overlap syndrome has eosinophilic predominance. Identifying the type of inflammation will aid in better management of COPD, but published studies show that induced sputum examination is more frequently used in asthma than COPD, with safety being the limiting factor. We aimed to determine the success and safety of sputum induction (SI) in COPD patients.

Methods: 116 stable COPD patients underwent SI. Success was defined as adequate sputum sample resulting in a cytospin sufficient to assess differential count while safety by the fall in FEV.

Results: The mean (SD) FEV% predicted post bronchodilator was 58.8 (17.8) and 59 (51.8%) patients had moderate COPD. Success was 98.28%. The procedure was safe with overall fall in FEV of 11.1% (5.1, 15.2). ≥20% fall was noted in 13 (11.4%) patients, 10-20% in 24 (21.0%) patients, and less than 10% in 29 (25.4%) patients while 48 (42.1%) had no fall. There was an inverse correlation between reversibility in FEV and percentage fall in FEV1; r=-0.437 and p=0.001. Stepwise multivariate linear regression showed reversibility as an independent predictor of fall in FEV; R=0.137.

Conclusions: Sputum induction is successful and safe in COPD. Even a fall in FEV>20% is reversible.