In a new study, researchers found that as much as two fifths (43%) of antibiotic prescriptions in the United States could be inappropriate.
Such a high degree of potentially unnecessary prescribing has important implications for antibiotic stewardship—efforts to reduce antibiotic use in response to the growing threat of antimicrobial resistance.
The research was conducted by a team of scientists based in Oregon.
Inappropriate antibiotic prescribing is a major public health problem.
Studies examining the appropriateness of antibiotic prescribing rely on a “documented indication” in patients’ medical records.
But these are not always required, leading to missing data and underestimates of antibiotic use.
In the study, the team estimated how often antibiotics are prescribed without a documented indication in non-hospital (ambulatory) care settings in the United States, and what factors are associated with a lack of documentation.
Using data from the National Ambulatory Medical Care Survey (NAMCS), they analyzed 28,332 visits (representing over 990 million visits across the United States) to office-based healthcare providers in 2015.
Of these visits, around 130 million (13%) involved an antibiotic prescription and were included in the study.
The researchers then used official diagnostic codes to identify whether each antibiotic prescription was accompanied by appropriate, inappropriate, or no documented indication.
According to their criteria, 57% (around 74 million) antibiotic prescriptions were deemed appropriate, while 25% (around 32 million) was considered inappropriate, and 18% (around 24 million) lacked either an appropriate or inappropriate documented indication.
This means that as much as 43% of prescriptions in this analysis could be potentially inappropriate.
When they looked at the data in more detail, they found that 20% of adults aged 18-64 and 22% of adults aged 65 years and older received antibiotics without a documented indication compared with 8% of patients under 18 years.
Patients who spent more time with a physician were more likely to receive an antibiotic without indication (15% for those with shorter visits vs 21% with longer visits).
Patients with chronic conditions were also more likely to receive an antibiotic without indication (22% for those with a chronic condition vs 14% for those without).
Primary care providers had a significantly lower percentage of antibiotic prescriptions without an indication documented (12%) compared with other specialists who commonly prescribe antibiotics (24%) as well as those in all other specialties (29%).
The team says the results are based on nationally representative survey data, so they are highly generalizable to the US population.
A comprehensive coding system is central to effective antibiotic stewardship. This should involve ensuring that diagnostic code is recorded every time an antibiotic is prescribed and that all infections are coded (not just those for which an antibiotic is being prescribed).
The study is published in The BMJ.
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