Almost of quarter of antibiotic prescriptions claimed by privately insured outpatients in the US are inappropriate, reveals a study of over 19 million patients published in The BMJ today.
Inappropriate prescribing was more common among adults than children, and the three most common reasons for inappropriate prescriptions were colds, chest infections and coughs.
Previous studies have shown widespread inappropriate prescribing of antibiotics to outpatients (patients not required to stay overnight at the hospital) in the US. But these studies used the older ICD-9-CM diagnosis codes and pre-2015 data, and they mainly focused on specific conditions, such as the common cold.
ICD-10-CM coding is the newest system used by doctors in the US to classify all diagnoses, symptoms and procedures recorded as part of hospital care.
So researchers in the US developed a comprehensive classification scheme which looked at whether each of the nearly 100,000 ICD-10-CM diagnosis codes justified the use of antibiotics in the treatment of 19.2 million US children and non-elderly adults in 2016.
They decided whether the codes "always", "sometimes" or "never" justified antibiotics in order to assess whether prescriptions were "appropriate", "potentially appropriate", "inappropriate" or "not associated with a recent diagnosis code".
Participants included both children and adults under 65 who were covered by private employer health care insurance, and records of their prescriptions were provided by the Truven Marketscan Commercial Claims and Encounters database.
Among the participants, three quarters were adults (75.9%) and over half were female (51.7%).
Of all prescriptions, nearly a quarter (23.2%) were inappropriate because they were only associated with illnesses such as the common cold and cough, which almost never require antibiotics.
And approximately 1 in 7 participants got at least one inappropriate antibiotic prescription in 2016.
Over a third (35.5%) of prescriptions were potentially appropriate, but the researchers say that many of these could have been inappropriate because illnesses such as sinusitis and sore throats have high rates of antibiotic prescriptions, even though many cases are not bacterial.
And among prescriptions not associated with a recent diagnosis code (28.5%), many could have been inappropriate if they were written based on phone or online consultations.
The authors highlight the limitations of the study, acknowledging that they relied on doctors to assign the correct codes and that other researchers may have made different classification decisions.
They also note that their findings "may not generalize to publicly insured US patients" or to all people who are privately insured.
However, they say that the study "provides the most recent and comprehensive estimates of outpatient antibiotic appropriateness in the US privately insured population to date."
And with many countries now investing in resources to combat the development of antibiotic resistance, the scheme could be "a valuable tool for policymakers and researchers" if adapted for use worldwide, they conclude.