A study of more than 13,000 patients with bronchiectasis has found that the colour of the phlegm they cough up is linked to the severity of their disease.
The information could be used to monitor patients’ health in a non-invasive way, allowing for earlier treatment when symptoms worsen.
The research, which isn’t yet peer-reviewed, was presented at the European Respiratory Society International Congress in Italy.
Bronchiectasis is a chronic and incurable lung condition where an infection like pneumonia or whooping cough causes airways in the lungs to become widened, allowing mucus to build up and making lungs more vulnerable to infection.
It is one of the most common lung conditions in the world and one of its main characteristics is coughing up phlegm, also called sputum.
According to Dr Megan Crichton, a postdoctoral researcher at the University of Dundee, UK, who presented the research, nearly three quarters of bronchiectasis patients produce sputum every day.
“When patients develop chest infections, their sputum colour darkens, and this colour change is due to a protein called myeloperoxidase, which is released from the inflamed cells; hence sputum colour can be used as a biomarker for inflammation,” says Crichton.
“We know that the level of lung inflammation is important for long term health in bronchiectasis, so we wanted to know whether the sputum colour, when assessed when the patient is healthy with no chest infection, had any relationship to long-term outcomes such as lung function and frequency and severity of exacerbations.”
Crichton and colleagues drew on data from the pan-European bronchiectasis registry, a long-term study which collects clinical data on bronchiectasis patients.
The researchers analysed the records of 13,484 patients from 31 countries. They compared sputum colour with the number of exacerbations (flare-ups), severity of those exacerbations, and deaths.
There are four types of sputum: mucoid, which is clear, frothy and greyish; mucopurulent, which is creamy and yellowish; purulent, which is thicker and darker yellow or green; and severe purulent, which is darker green or brown and sometimes contains blood.
“We found an increased risk of exacerbations, hospitalisations and death with more purulent sputum. For each 1-point increase in sputum purulence, there was a 12% increased risk of death,” says Crichton.
“As this is a large study conducted across multiple countries and with five years of follow-up data, it provides the evidence that sputum colour reflects prognosis.”
Crichton says that phlegm colour could be useful for both patients and clinicians to monitor health.
“Sputum sampling is non-invasive for patients, and they are actively encouraged to cough up sputum whenever possible to improve their lung function,” she says.
“Knowing that by looking at their sputum colour as a means of self-monitoring and self-management can empower patients and gives them some control over their condition, which we know is important for improving patient quality of life.”
The researchers are hoping to introduce a sputum colour chart into clinical practice.
“The findings from this study offer doctors and patients an easy, non-invasive way of monitoring their symptoms,” says Professor Carlos Robalo Cordeiro, president of the European Respiratory Society, and dean of the faculty of medicine at the University of Coimbra, Portugal, who was not involved with the research.
“If this is rolled out into clinical practice, it could make a real difference to managing this disease, and allow clinicians to intervene at an earlier stage if it becomes clear from the change in sputum colour that patients’ symptoms are worsening.”