A closer analysis of antibiotic prescription practices leads to better prescribing for sore throats

Across general practice in New Zealand, it is common for people with pharyngitis (a sore throat) to be treated with a course of antibiotics.

“Laboratories in New Zealand and worldwide have a responsibility to provide clear guidance to GPs on the most appropriate use of antibiotics, and this continues to be an important part of our scientific work at Awanui,” says Microbiologist Dr Max Bloomfield.

Max and his team recently published research on the Oxford Academic website titled ‘Effect of directive laboratory comments on prescribing response to positive throat swab cultures’. In the article, they examined the effect of updated guidance provided by Awanui to Wellington and Hutt based GPs on antibiotic prescribing for sore throats.

The team includes Awanui microbiologists Michelle Balm and Tim Blackmore, Head of Department Koen Van Der Werff, and Wellington-based GP Sue Todd. The research builds on their previous work aimed at improving antimicrobial stewardship and reducing the risk of overprescription, or antibiotics being prescribed when not required, and patient care.

Identifying the risk of over-prescription

“The District Health Boards updated their HealthPathways guidance to GPs in 2021 to recommend shorter antibiotic treatment for patients without risk factors for acute rheumatic fever (ARF) and positive throat swab cultures for group A strep (GAS) or Streptococcus dysgalactiae,” says Max.

“Unfortunately, our own audit data had shown most low-risk patients across Wellington and Hutt who returned a positive throat swab result were still being given the longer treatment course of ten days antibiotics, instead of the shorter recommended course of five to seven days.

“To try to improve practice, we altered the comments that attached to positive throat swab cultures to give clear guidance on the recommended treatment durations. Having taken this step, the team needed to understand whether it had been effective, and if the research could demonstrate change in prescription behaviour.”  

Changes to the lab comments

The updated comments from Awanui came into effect in September 2022. They recommended antibiotics be prescribed for only five days to patients with low ARF risk and only if symptoms are severe. For patients without severe symptoms, antibiotics were not recommended at all and for Māori and Pasifika patients and others at risk of ARF, the recommendation remained ten days.

The comments made clear Streptococcus dysgalactiae is not a cause of ARF and the benefit of antibiotic treatment is uncertain. For patients with severe symptoms, only five days treatment is required.

Methodology and results

Max and the team assessed test results for patients in the Wellington region who had returned a positive throat swab culture from October 2021 to March 2023.

The data was split into two groups. The first cohort of over 14,000 test results were reported before the changes to the guidance, with around 7600 results reported after the update had been made. The National Pharmaceutical Collection, which records community dispensing of antibiotics, was also used to determine which antibiotic treatments had been prescribed and for how long.

“The research focused on patients who had not already been started on antibiotics when the culture result was reported by the lab,” says Max.

“Our analysis showed the updated comments had an immediate effect on prescribing following positive throat swab cultures. The average treatment duration for GAS positive throat swabs dropped from ten to seven days. Importantly, for Māori and Pasifika patients, the treatment durations remained at the recommended ten days.

“The research also found the percentage of patients receiving a ten day course of antibiotics for GAS dropped from 63 percent to 37 percent, while those receiving a five day treatment increased to just under 15 percent, from around 2 percent.”

Max says for patients who tested positive for Streptococcus dysgalactiae, the average course of treatment dropped from seven days to zero after the guidance change. The percentage of those receiving a ten day treatment course dropped from almost 42 percent to 14.6 percent and the change for a five day course increased from 3.4 percent to just over 24 percent.

Research outcomes

“We were very impressed by the response we saw from prescribers to the updated comments.” says Max.

“Our latest research demonstrated the new guidance resulted in GPs changing their approach to prescribing antibiotics for patients not at risk of ARF and who had returned a positive throat swab culture. It was particularly pleasing, because this was an intervention which required almost no resource to implement but has led to a significant positive effect on our community in terms of reducing unnecessary antibiotic use.”

Max says the updated recommendations build on the changes happening at Awanui on reporting patient results.

“By providing clear and direct instructions to GPs, we are adding credibility to our treatment guidelines. The research into improving and enhancing antimicrobial stewardship will continue at Awanui, including capturing more data, addressing gaps in the knowledge, with the potential to be applied to other regions and types of microbiology results and delivering benefits to patients across New Zealand.”   

You can read the full article in the Journal of Antimicrobial Chemotherapy

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