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Study finds nearly 25% of antibiotics are unnecessarily prescribed

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January 22, 2019

Kao-Ping Chua, MD
Kao-Ping Chua

In a recent study examining outpatient antibiotic prescriptions filled by privately insured patients, researchers found that overall, 23% of antibiotic prescription fills were unnecessary.

Kao-Ping Chua, MD, assistant professor of Pediatrics, University of Michigan Medical School, C.S. Mott Children’s Hospital, told Infectious Disease News that unlike prior estimates, the proportion of inappropriate antibiotic prescriptions is based on the updated ICD-10-CM codes.

“The most recent national studies on antibiotic overuse in the U.S. used older data from the first half of this decade, “Chua said. “There weren’t any national studies that used more recent data, because our methods of measuring antibiotic overuse were all based on an outdated system of classifying diagnosis codes — ICD-9-CM — which was replaced by ICD-10-CM in the U.S. in October 2015. To address this gap, we developed an ICD-10-CM-based method of measuring antibiotic overuse, then assessed the appropriateness of antibiotic prescriptions among 19.2 million privately insured children and nonelderly adults aged zero to 64 years in 2016 — a population that represented approximately one in eight privately insured Americans.”

According to the study, researchers used a classification scheme to determine whether each of the 91,738 ICD-10-CM diagnosis codes “always,” “sometimes” or “never” justified antibiotics. This scheme was used to classify all diagnosis codes during a look-back period that began 3 days before antibiotic prescription fills and ended on the day fills occurred. Using this, researchers determined the proportion of fills in each of four categories: “appropriate,” “potentially appropriate,” “inappropriate” and “not associated with a recent diagnosis code.”

Results showed that of the 15.2 million antibiotic prescriptions filled by the sample, 23.2% were not medically justified. Additionally, researchers found that 28.5% were not associated with any documented diagnosis.

“Our main finding was that almost a quarter of antibiotic prescriptions were written for diagnoses that would get better on their own without antibiotics,” Chua said. “Because the rate of antibiotic use was so high in our study — more than 800 prescriptions per 1,000 patients — we found that approximately one in seven patients received unnecessary antibiotic prescriptions during 2016.”

Although the proportion appears to be lower than a CDC estimate issued in 2016, Chua said he does not think direct comparisons are useful due to differences in data, populations and measurement.

“First, the CDC’s numbers were based on a 2016 study published in JAMA that analyzed data from emergency departments and office-based visits in 2010 and 2011. In contrast, we used data from privately insured patients in 2016 that captured prescribing across more a broader variety of settings,” Chua said.

Additionally, Chua explained that the 23% they arrived at refers to antibiotics written for conditions that do not justify their use, whereas the figure of 30% from the CDC reflects both these types of antibiotics as well as their best estimate of the rate of unnecessary prescriptions that are written for conditions that only sometimes justify antibiotics — like sinusitis.

“Antibiotic prescribing is a major driver of the development of bacteria that are resistant to antibiotics. These antibiotic-resistant bacteria are one of the greatest threats to health worldwide. The CDC estimates that every year, 2 million people in the U.S. develop infections with antibiotic-resistant bacteria, and 23,000 die,” Chua said. “Given this, it is urgent for providers to eliminate inappropriate antibiotic prescribing, both for the sake of their own patients and for society more broadly. Unfortunately, our finding that one out of seven patients receive unnecessary antibiotics every year demonstrates how widespread the problem still is and how far we need to go.” – by Caitlyn Stulpin

Disclosures: The authors report no relevant financial disclosures.

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