Relation of sputum colour to bacterial load in acute exacerbations of COPD

When COPD patients present with an exacerbation, one cannot verify a bacterial cause of an exacerbation without time-consuming laboratory analyses. This makes it difficult to decide up front if antibiotic treatment is needed. Therefore, in clinical practice sputum colour and purulence are often used.

To determine whether sputum colour and purulence, assessed by the Stockley colour chart, correlated with overall bacterial load in COPD patients admitted for an exacerbation. To check the robustness of the colour and purulence assessment, we correlated the changes in these parameters and the corresponding change in bacterial load in sputum over the first seven days of hospitalisation.

Twenty-two COPD patients admitted to the hospital for an exacerbation were included. During the first seven days daily sputum samples were collected.

A very weak association between bacterial load and sputum colour was found. There was no difference in bacterial load between patients with purulent sputum or not. Also, no consistent relationship between change in sputum colour and change in bacterial load during admission was found.

The very weak association between bacterial load and sputum colour confirms concerns over the usefulness of the colour chart. The distinction between purulent and mucoid sputum at exacerbation is insufficient for distinction between patients who are likely to benefit from antibiotic therapy and those who are not. Complementary studies are needed to determine which other, easily measurable factors can be used as predictors for an indication for use of antibiotics; sputum colour is not the one.