Phlegm color doesn’t matter

Contrary to conventional wisdom, the color of one’s phlegm is not a good indicator of whether one would benefit from taking antibiotics. So says a new study by a European consortium of scientists led by Chris Butler of Cardiff University.

Many patients and physicians believe that coughing up yellow or green sputum is indicative of a bacterial infection that can be successfully treated with antibiotics, whereas coughing up clear or no phlegm might be more diagnostic of an illness that cannot be treated with antibiotics. In this study, two sets of comparisons were made.

First, is colored phlegm associated with feeling ill and/or with antibiotic prescription? In other words, do patients presenting with green phlegm tend to feel worse than patients with clear phlegm? And how often do the two groups receive prescriptions for antibiotics? Not surprisingly, antibiotics were most often given to patients with colored phlegm. However, those patients did not report more severe symptoms than the patients with no sputum (who had not received prescriptions).

Second, the researchers asked whether the antibiotics actually did alleviate symptoms more often in patients with colored sputum (who were presumably suffering from bacterial infections) than in those with clear or no sputum. The answer was ‘no’. Neither the color of the sputum patients coughed up nor the magnitude of their symptoms was predictive of whether they had bacterial infections that could benefit from antibiotic treatment.

I love reading stories that show that I’ve been wrong about something. It highlights exactly why you can’t take things for granted, but must actually study them. And sorry, no pretty pictures with this post.