Despite efforts to reduce the number of inappropriate antibiotic prescriptions for outpatients, evidence suggests that many unnecessary prescriptions are still being written. Previous studies of this problem used diagnosis codes in ICD-9-CM (International Classification of Diseases, Ninth Revision, Clinical Modification), which was replaced by ICD-10-CM in the United States in 2015. To comprehensively measure the appropriateness of outpatient antibiotic prescriptions using more up-to-date information, researchers developed a novel classification scheme of diagnosis codes in ICD-10-CM. Using this classification scheme and a 2016 national claims database, they studied a large cohort of privately insured children and adults.
Pharmacy prescription fills were classified as "appropriate" (associated with at least one "always" diagnosis code), "potentially appropriate" (associated with at least one "sometimes" code but no "always" codes), "inappropriate" (associated with only "never" codes), and "not associated with a recent diagnosis code." The study cohort included more than 19.2 million children and adults, who filled more than 15 million outpatient antibiotic prescriptions in one year. Of these, the researchers deemed 12.8% appropriate, 35.5% potentially appropriate, and 23.2% inappropriate; 28.5% weren't associated with a recent diagnosis code. They found that 14.1% of enrollees filled at least one inappropriate prescription in 2016.
The authors caution that inaccurate or incomplete coding can lead to misclassification. They also note that their classification decisions may have differed from those of other researchers. In addition, this study was based on privately insured patients, didn't include prescriptions paid for out of pocket, and didn't consider choice of agent or duration of treatment. The researchers suggest that their classification scheme can be used by others to measure the appropriateness of antibiotic prescribing in the United States and can also be adapted for use by researchers in other countries.
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