Relationship of sputum color to nature and outpatient management of acute exacerbations of COPD

Study objectives: To stratify COPD patients presenting with an acute exacer bation on the basis of sputum color and to relate this to the isolation and viable numbers of bacteria recovered on culture. Design: Open, longitudinal study of sputum characteristics and acute-phase proteins. Setting: Patients presenting to primary-care physicians in the United Kingd om. Patients were followed up as outpatients in specialist clinic. Patients: One hundred twenty-one patients with acute exacerbations of COPD were assessed together with a single sputum sample on the day of presentati on (89 of whom produced a satisfactory sputum sample for analysis). One hun dred nine patients were assessed 2 months later when they had returned to t heir stable clinical state. Interventions: The expectoration of green, purulent sputum was taken as the primary indication for antibiotic therapy, whereas white or clear sputum w as not considered representative of a bacterial episode and the need for an tibiotic therapy. Results: A positive bacterial culture was obtained from 84% of patients spu tum if it was purulent on presentation compared with only 38% if it was muc oid (p < 0.0001). When restudied in the stable clinical state, the incidenc e of a positive bacterial culture was similar for both groups (38% and 41%, respectively). C-reactive protein concentrations were significantly raised (p < 0.0001) if the sputum was purulent (median, 4.5 mg/L; interquartile r ange [IQR], 6.2 to 35.8). In the stable clinical state, sputum color improv ed significantly in the group who presented with purulent sputum from a med ian color number of 4.0 (IQR, 4.0 to 5.0) to 3.0 (IQR, 2.0 to 4.0; p < 0.00 01), and this was associated with a fall in median C-reactive protein level to 2.7 mg/L (IQR, 1.0 to 6.6; p < 0.0001). Conclusions: The presence of green (purulent) sputum was 94.4% sensitive an d 77.0% specific for the yield of a high bacterial load and indicates a cle ar subset of patient episodes identified at presentation that is likely to benefit most from antibiotic therapy. All patients who produced white (muco id) sputum during the acute exacerbation improved without antibiotic therap y, and sputum characteristics remained the same even when the patients had returned to their stable clinical state.