Up to 43% of Antibiotic Prescriptions in the United States May Be Inappropriate

National data from the US Centers for Disease Control and Prevention (CDC) indicate 2.8 million antibiotic resistant infections occur each year, leading to 35,000 deaths annually. The same CDC reporting noted that at least 30% of antibiotics prescribed in US ambulatory care settings are unnecessary.

Programs assessing antibiotic use rely on the presence of a documented indication in patients’ medical records, with frequency of inappropriate use determined by such indications. Documentation is not, however, universally required. Missing indication data may lead to underestimates regarding the actual scope of inappropriate antibiotic use.

The investigators of a new study published in the BMJ sought to identify how frequently antibiotics are prescribed without a documented indication. The study team discovered that 18% of antibiotic prescriptions in a nationally representative sample of ambulatory clinic encounters had no documented indication. It is estimated that on the national level 24 million antibiotic prescriptions do not have a documented indication.

Results were gathered from 28,332 sample visits, representing over 990 million ambulatory care visits nationally. About 130 million of these visits involved an antibiotic prescription.

Investigators gathered information through the National Ambulatory Medical Care Survey, an annual national survey conducted by the National Center for Health Statistics. The National Ambulatory Medical Care Survey reports 5 international classification of disease codes.

On the basis of the codes available for each visit investigators considered an indication “appropriate” if a bacterial infection or other condition for which antibiotics are always or sometimes indicated was documented.

A prescription was considered “inappropriate” if it was related to a condition for which antibiotics may commonly be prescribed, such as upper respiratory tract infections, but for which there is no indication. “No documented indication” referred to those prescriptions for which neither preceding category was applicable.

According to criteria, 57% of antibiotic prescriptions were deemed appropriate, 25% inappropriate, and 18% had neither appropriate nor inappropriate documentation. That leaves up to 43% of prescriptions potentially inappropriate.

Investigators also evaluated risk factors for prescription of antibiotics without a documented indication. Age, provider specialization, time of year, and presence of a chronic condition were identified.

It was discovered that patients were more likely to receive antibiotics if they were male (61%) and non-Hispanic white (58%). Patients above 18 years of age were more likely to receive antibiotics than those younger. Chronic conditions were associated with more prescribing without an indication, with rates at 22% for patients with a chronic condition compared to 14% for those without.

Patients who had longer visits were more frequently (21%) prescribed an antibiotic without indication than those who had shorter visits (15%).

Provider characteristics also were found to play a role in antibiotic prescription. Primary care providers had a lower percentage (12%) of antibiotic prescriptions without indication when compared with other specialists who commonly prescribe antibiotics (24%) or those in all other specialties (29%).

When antibiotics are prescribed without an indication, the appropriateness of prescriptions cannot be determined. This impedes efforts at antimicrobial stewardship, which need an accurate sense of the scope of the problem to even begin addressing it.

“Our study identified several independent risk factors for antibiotic prescribing without a documented indication; these may be useful in directing initiatives aimed at improving documentation. With 60% of antibiotic expenditure and up to 90% of antibiotic use originating in ambulatory care settings, more focus is needed to support well informed stewardship efforts beyond the hospital,” study authors wrote.