Finding | Observations | [Refs.] | |
Clinical | Presence of the three cardinal symptomsr | May be a predictor of response to antibiotics | 19 |
Sputum purulence | Correlateds with MPO concentration and bacterial load | 9, 35, 43 | |
Fever | Might be unusual in bacterial AECBs, but frequent during viral infections | 45 | |
Inflammatory | Blood leukocytosis (neutrophilia) | Not or poorly documented; interference of oral steroids | 12 |
Sputum neutrophilia | Increases during AECBs, not validated in longitudinal studies | 10 | |
Increased sputum neutrophil elastase | Possibly biased via its correlation with the severity of AECBs | 22 | |
Microbiological | Sputum bacteriology (Gram stain, culture) | Positive in half of stable COPD patients (colonization); bacterial load>106 cfu·mL−1 (or >105 for Streptococcus pneumoniae); protected brush specimens more accurate but less feasible in routine practice | 38, 46–50 |
Serology (strongly positive or ≥ 4-fold titre increase) | Mainly ′retrospective′ diagnosis; chronic carriage may also be associated with high antibody titres | 31–51 |
MPO: myeloperoxidase
COPD: chronic obstructive pulmonary disease
cfu: colony-forming units