A comparison of induced and expectorated sputum for the microbiological diagnosis of community acquired pneumonia

Background: Sputum induction has proved useful in the diagnosis of Pneumocy stis carinii pneumonia and mycobacterial infections but there are scant dat a on its use in the diagnosis of community-acquired pneumonia (CAP). Object ive: To better define the usage of sputum induction by hypertonic saline in the setting of CAP. Methods: A retrospective review of records of patients admitted to a community teaching hospital in the year 1995 with a diagnosi s of CAP. Results: Of 492 patients admitted with CAP, 71 (14%) had attempte d sputum induction. A group of 66 patients with CAP and attempted sputum co llection by spontaneous expectoration was compared with this group. Sputum induction failed to yield a sample in 22 patients (31%). Forty-five of 49 p atients (92%) with induced sputum had received prior antibiotics as compare d to 23 of 34 patients (68%) with expectorated samples (p < 0.05), due to s putum induction often being attempted later in the hospital course. The dia gnostic yield of sputum induction was 14 of 71 (20%) compared to 16 out of 66 (24%) for attempted spontaneously expectorated samples. Antibiotic thera py was changed for 5 of 34 patients (15%) who spontaneously expectorated sa mples and for 9 of 49 patients (18%) with successful induction. Conclusions : Sputum induction is effective in obtaining sputum in some patients with C AP who fail to expectorate a sample. Attempting induction early, preferably before starting antibiotics, may increase its diagnostic yield. Copyright (C) 2000 S. Karger AG, Basel.