A new analysis of antibiotics doled out during US ambulatory care visits in 2015 indicates that more than 40% were inappropriate, and nearly 1 in 5 prescriptions had no documented reason for being written.
In a study published yesterday in the British Medical Journal (BMJ), researchers looking at survey data on more than 28,000 sample visits to office-based healthcare providers in 2015—a sampling that represents 990.9 million visits nationwide—found that antibiotics were prescribed in 13.2% of visits. Of the 130.5 million antibiotic prescriptions given out during these visits, only 57% were for a bacterial infection or other condition for which antibiotics are commonly, and appropriately, prescribed.
Twenty-five percent of the antibiotic prescriptions analyzed were deemed inappropriate because they were written for conditions, like upper respiratory infection, for which antibiotics aren't indicated but are commonly prescribed. But 18%—representing roughly 24 million prescriptions—lacked either an appropriate or inappropriate indication.
"When there's no indication documented, it's reasonable to think that at least some of the time, the prescription was written without an appropriate indication present," lead study author Michael J. Ray, MPH, a researcher at Oregon State University's College of Pharmacy, said in a university press release.
The problem of undercoding
To determine whether the prescriptions were appropriate or inappropriate, Ray and his colleagues looked at the ICD-9-CM codes associated with each visit in which an antibiotic was prescribed. Only five of these codes, which are used by physicians to classify a diagnosis in a patient's medical record for billing purposes, were included in the data from the 2015 National Ambulatory Medical Care Survey (NAMCS), a survey describing a sample of patients' visits.
The researchers note that even if more ICD-9-CM codes had been available to analyze, at best, 15% of the visits would have still lacked a documented indication for an antibiotic.
The most common diagnoses reported among the "no indication" group were unspecified essential hypertension (11%), diabetes mellitus without mention of complication (8%), and other specified aftercare (7%).
In analyzing additional patient data from the NAMCS records, the researchers determined that adult men (adjusted odds ratio [aOR], 2.3; 95% confidence interval [CI], 1.02 to 5.3), patients who spent more than 17 minutes with providers (aOR, 1.6; 95% CI, 1.1 to 2.5), and patients who saw non-primary care specialists (aOR, 2.1; 95% CI, 1.2 to 3.7) were more likely to receive an antibiotic without an indication.
The analysis also found that sulfanomides (aOR, 4.9; 95% CI, 1.5 to 15.7) and urinary anti-infectives (aOR, 3.1; 95% CI, 1.3 to 7.6) were the antibiotics most likely to be prescribed without an indication.
The study adds to a well-established body of research illustrating the problem of inappropriate outpatient antibiotic prescribing in the United States. The most widely cited study is a 2016 paper in JAMA that found that 30% of oral antibiotics prescribed for outpatients were inappropriate. Subsequent studies have indicated the proportion of outpatient prescriptions considered inappropriate may be even higher.
But as Ray and his co-authors note, the previous estimates have typically relied on documented diagnosis codes to classify the prescriptions as appropriate or inappropriate. As a result, they believe those studies may underestimate the problem.
"The primary objective of this study was to highlight the potential degree of misclassification that may occur due to under-coding," they write. "Our work complements previous work in this area by assessing the potential effect that prescribing without a documented indication may have on the estimated burden of unnecessary antibiotic use."
They add that the identification of risk factors associated with antibiotic prescribing without a documented indication may be useful for antibiotic stewardship efforts.
See also:
Dec 11 BMJ study
Dec 11 Oregon State University press release
