Study objectives: To stratify COPD patients presenting
with an acute exacerbation on the basis of sputum color and to relate
this to the isolation and viable numbers of bacteria recovered on
Design: Open, longitudinal study of sputum
characteristics and acute-phase proteins.
Patients presenting to primary-care physicians in the United Kingdom.
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 presentation (89 of whom produced a satisfactory
sputum sample for analysis). One hundred nine patients were assessed 2
months later when they had returned to their stable clinical
Interventions: The expectoration of green,
purulent sputum was taken as the primary indication for antibiotic
therapy, whereas white or clear sputum was not considered
representative of a bacterial episode and the need for antibiotic
Results: A positive bacterial culture was
obtained from 84% of patients sputum if it was purulent on
presentation compared with only 38% if it was mucoid (p < 0.0001).
When restudied in the stable clinical state, the incidence 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 range [IQR], 6.2 to 35.8). In the stable
clinical state, sputum color improved significantly in the group who
presented with purulent sputum from a median color number of 4.0 (IQR,
4.0 to 5.0) to 3.0 (IQR, 2.0 to 4.0; p < 0.0001), 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).
presence of green (purulent) sputum was 94.4% sensitive and 77.0%
specific for the yield of a high bacterial load and indicates a clear
subset of patient episodes identified at presentation that is likely to
benefit most from antibiotic therapy. All patients who produced white
(mucoid) sputum during the acute exacerbation improved without
antibiotic therapy, and sputum characteristics remained the same even
when the patients had returned to their stable clinical