Success and safety of sputum induction in the clinical setting

Abstract

It has previously been reported that sputum induction is successful and safe in the clinical research setting. The authors examined the success and safety of sputum induction in routine clinical practice in patients with asthma or chronic airflow limitation of varying severity. Records of 304 patients with asthma and 25 with smoking related chronic airflow limitation were examined retrospectively. All had sputum induced as part of their routine clinical evaluation. When the baseline post salbutamol forced expiratory volume in one second (FEV1) was ≥70% predicted, the inductions consisted of inhalation of an aerosol of 3%, 4% and 5% saline, each given for 7 min. If the FEV1 was <70%, or there were other reasons for concern, the inductions were initiated with normal saline for shorter periods. Inhalations were discontinued when sputum was obtained or when there was a fall in FEV1 ≥20%. Success was identified by obtaining nonsquamous total and differential cell counts containing macrophages, and safety by the fall in FEV1. The overall success was 93%. The procedure was safe even amongst patients with an FEV1 of <60% and <1 L. Of 77 patients with an FEV1 between 40-59%, 8% fell by ≥20% and of 35 patients with an FEV1 <40%, 6% fell by 20%. Carefully standardized sputum induction can be successful and safe in patients with asthma or chronic airflow limitation in clinical practice, even when moderate or severe airflow limitation is present.