Study: 30% of outpatient antibiotic prescriptions unnecessary

Pill packets

Global Panorama / Flickr cc

Approximately 30% of all oral antibiotics prescribed in US outpatient settings are unnecessary, and antibiotic prescribing rates are higher overall for young children and people living in the South, according to a study yesterday in the Journal of the American Medical Association (JAMA).

The Centers for Disease Control and Prevention (CDC), which was involved in the study, said the findings suggest that 47 million needless prescriptions are written each year. This puts patients at unnecessary risk for allergic reactions or the sometimes deadly diarrhea caused by Clostridium difficile, the agency said in a press release.

The Obama administration's 2015 National Action Plan for Combating Antibiotic-Resistant Bacteria (CARB) set the goal of reducing antibiotic use by half in outpatient clinics by 2020, though antibiotic prescription practices in ambulatory care settings are poorly understood.

To address knowledge gaps and provide baseline estimates of appropriate outpatient antibiotic use, researchers from the CDC and the Pew Charitable Trusts (PCT) evaluated 184,032 visits to outpatient clinics and Emergency Departments (EDs) as captured by the 2010-11 National Ambulatory Medical Care Survey (NAMCS) and the National Hospital Ambulatory Medical Care Survey (NHAMCS).

To the authors' knowledge, the study represents the first national estimate of appropriate outpatient antibiotic use that considers how prescription practices vary between geographic regions and age groups.

Establishing baselines for appropriate use

A variety of methods were used to estimate how many antibiotic prescriptions were appropriate. PCT convened experts to estimate whether some antibiotics were necessary based on national prescribing guidelines, which largely advocate against antibiotic treatment for bronchitis, bronchiolitis, viral upper respiratory infections, asthma, allergies, influenza, viral pneumonia, and nonsuppurative otitis media.

In instances where antibiotic treatment guidelines were ambiguous or dependent on clinical context, such as in diagnoses of sinusitis and suppurative otitis media, the authors used the geographic region with the lowest prescription rate as a baseline for appropriate use.

Baseline rates for appropriate antibiotic prescriptions to treat sinusitis were 59 per 1,000 population for children 0 to 19 years, 27 per 1,000 for people ages 20 to 64, and 37 for people 65 years and older. The authors chose 138 prescriptions per 1,000 population of children and 6 prescriptions per 1,000 adults ages 20-64 as baselines for necessary treatment of suppurative middle ear infections.

Experts chose not to set baselines or goals for conditions in which antibiotics are often overused but also often necessary and appropriate, including urinary tract infections, pneumonia, and miscellaneous bacterial infections, the authors said.

Antibiotics were prescribed in 12.6% of 184,032 outpatient or ED visits from 2010 to 2011. Conditions with the highest prescription rates included sinusitis (56 prescriptions per 1,000 population), suppurative otitis media (47 per 1,000), and pharyngitis (43 per 1,000). In total, 221 prescriptions per 1,000 population were prescribed for acute respiratory infections.

Antibiotic use varied significantly by geographic region, with the lowest rate observed in the West (423 prescriptions per 1,000 population) and the highest in the South (553 per 1,000). Rates were highest in the West and the South for infants ages 0 to 2 (1,071 per 1,000 and 1,492 per 1,000, respectively).

Nationwide, infants ages 0 to 2 had significantly higher rates of antibiotic treatment compared with other age groups, with an average of 1,287 outpatient visits per 1,000 resulting in a prescription, the authors said.

Far too many prescriptions for respiratory illnesses

Overall, the authors estimated that 506 prescriptions were written per 1,000 populaton annually during the study period, but that only 353 (70%) of these were appropriate and necessary. About half of all antibiotics prescribed for acute respiratory conditions (111 of 221 prescriptions per 1,000) were deemed inappropriate, the authors said.

Antibiotic treatment of sore throat, which is warranted only in cases of streptococcal pharyngitis, was far above previously published estimates for strep infections, the authors said. A majority of outpatient visits due to sore throat (56.2% of children and 72.4% of adults) resulted in an antibiotic prescription, though other studies have estimated pediatric and adult rates of strep throat to be around 37% and 18%, respectively.

Antibiotics were prescribed for numerous inappropriate conditions, including during 9% of outpatient visits for asthma or allergy, 26% of visits for viral upper respiratory infections, and 11% of visits for acne, the authors said. Prescription rates for all three diagnoses were highest during visits by patients 0 to 19 years (14% asthma/allergy, 42% viral upper respiratory infection, and 22% acne).

Factors driving inappropriate antibiotic prescribing may include over-diagnosis of common conditions, a need to please patients, and patient race, the authors said. The CDC advocates training and antibiotic stewardship interventions (eg, prescription delay periods, prescribing audits) for clinicians and encourages patients to question antibiotic prescriptions when they appear unnecessary.

Opportunities for 5-year improvement

Though the study refines estimates of appropriate antibiotic use in outpatient settings, the authors identified several limitations that likely caused underestimation of rates of unnecessary prescriptions. The NAMCS and NHAMCS exclude several outpatient environments that prescribe antibiotics, such as urgent care, retail clinics, federal clinics, and telemedicine. Some clinicians with prescribing powers, such as nurse practitioners and physician assistants, were also included only in small, non-representative numbers.

Given the finding that 30% of outpatient antibiotic prescriptions are unnecessary, clinics and EDs need to reduce inappropriate prescribing practices by 15% by 2020 to reach the CARB goal. Geographic variation in antibiotic use and the lack of evidence for poor outcomes in low-prescribing regions demonstrates that this reduction is possible, the authors said.

"This estimate of inappropriate outpatient antibiotic prescriptions can be used to inform antibiotic stewardship programs in ambulatory care by public health and health care delivery systems in the next 5 years," the authors said.

Need for future research

In a commentary yesterday in the same issue of JAMA, Pranita D. Tamma, MD, MHS, and Sara E. Cosgrove, MD, MS, of the Johns Hopkins University School of Medicine discussed the study's contributions to a national understanding of inappropriate prescribing practices.

Because of the diverse methods used to estimate a baseline for appropriate antibiotic use, the study likely underestimates inappropriate prescriptions for pneumonia, urinary tract infection, sinusitis, and suppurative otitis media, they wrote. Additionally, the exclusion of numerous outpatient settings likely results in a substantial underestimate of inappropriate prescriptions, they added, noting that one study estimated that 10% of antibiotics are prescribed by dentists.

Future studies will benefit from obtaining more information on the duration of antibiotic treatment and classes used, as overprescription of cephalosporins and fluoroquinolones in outpatient settings is a contributor to growing antibiotic resistance, Tamma and Cosgrove said.

The two authors recommend interventions to evaluate changes in clinician documentation and coding that may incorrectly appear to be reductions in inappropriate prescribing practices and to institute better point-of-care diagnostic testing.

"Now that baseline estimates about outpatient antibiotic prescribing have been determined, future work needs to focus on interventions targeting both clinicians and patients to help reach the national goal," Tamma and Cosgrove said.

May 3 JAMA study

May 3 JAMA commentary

May 3 CDC press release

This week's top reads

Our underwriters