NEW YORK (Reuters Health) – Doctors shouldn’t rely on sputum color when deciding whether to prescribe antibiotics to cough patients, according to a new study in the European Respiratory Journal.

Researchers led by Dr. Christopher Butler of Cardiff University in the UK found that patients with yellow or green sputum were prescribed antibiotics more than three times as often as patients not producing sputum. But antibiotic treatment did not help those patients recover any faster.

The research, part of the Genomics to combat Resistance against Antibiotics in Community-acquired LRTI in Europe (GRACE) study, took place in 13 European countries and included 3,402 adults with acute cough or lower respiratory tract infection.

Primary care providers who participated in the study recorded patients’ symptoms and medical histories along with their own management of each case, including whether or not they prescribed antibiotics. Patients also kept a diary where they rated daily symptoms including cough, fever, and how unwell they felt.

Enough data was provided for 2,419 patients who were included in the final analysis.

When patients were first seen by their primary care doctor, 26.4% were producing yellow sputum and 18.6% were producing green sputum; 80.2% of them reported feeling generally unwell.

Doctors were more likely to prescribe antibiotics to patients who were producing discolored sputum – but not patients producing white or clear sputum – compared to those who didn’t produce any sputum (OR = 3.2, 95% CI: 2.1-5.0). They prescribed antibiotics to patients who reported feeling generally unwell and those who did not report feeling unwell at the same rate.

Sputum color was not linked with the severity of each patient’s symptoms, and antibiotic treatment in patients with discolored sputum did not speed improvement of symptoms.

Patients with yellow or green sputum feeling mildly unwell reported initial symptom scores of 23.3 out of 100 (patients not prescribed antibiotics) and 21.3 (patients prescribed antibiotics). After 7 days, those not taking antibiotics recorded an average symptom score of 4.3, compared to 3.9 in those taking antibiotics. There was also not a noticeable difference in symptom improvement with antibiotics for patients producing green or yellow sputum, or for those producing any discolored sputum and feeling moderately or severely unwell.

A separate analysis including only patients with asthma, chronic obstructive pulmonary disease, or those over 65 also found that antibiotic treatment didn’t improve recovery in patients with discolored sputum and who were feeling unwell.

The authors cite recommendations from the European Respiratory Society and the U.S. Centers for Disease Control and Prevention about the need to selectively decide which patients might benefit from antibiotic treatment. They conclude that it is essential for doctors to follow those recommendations more closely to address the pressing threat of antibiotic resistance.

“The findings suggest that physicians should not rely on sputum colour, either on its own or in conjunction with patients feeling generally unwell, when deciding whether or not to prescribe an antibiotic for such patients,” Butler and his colleagues write.

“Implementing this evidence is likely to reduce antibiotic prescribing for those with acute cough who are unlikely to benefit from antibiotic treatment and thus contribute to containing antibiotic resistance.”

Euro Resp J