Seeing the (W)hole in Antibiotic Use

Reviewed by: Jesse Sutton, PharmD, Veterans Affairs Salt Lake City Health Care System 

Two recent articles highlight both the importance of outpatient antibiotic stewardship and limitations in the assessment of outpatient antibiotic appropriateness. Ray and colleagues evaluated the appropriateness of antibiotic prescribing in Ambulatory Care visits across the United States. Feller and colleagues quantified the contribution of post-discharge antibiotics to overall antibiotic use associated with hospital visits at Veterans Affairs hospitals.  

Ray and colleagues assessed outpatient antibiotic prescribing in a cross-sectional study of 28 thousand sample visits from the US 2015 National Ambulatory Medical Care Survey. This sample represents 991 million ambulatory care visits nationwide. Prescriptions were classified as appropriate (e.g. pneumonia, cystitis), inappropriate (e.g. acute bronchitis, sinusitis), or no documented indication based on ICD-9-CM diagnosis codes and a previously published classification scheme. Antibiotics were prescribed in 13% of the 28 thousand sampled visits. There were two notable findings.  First, approximately 57% of prescriptions were appropriate, 25% were inappropriate, and 18% had no documented indication. The 57% rate of appropriate prescriptions is higher than previous studies and likely an overestimate, as it assumes the coded diagnoses were completely accurate. Second, the 18% of sample visits without an indication correlates to 24 million visits nationwide, highlighting a major limitation in the accuracy of large-scale appropriateness assessments relying on diagnosis codes. Factors associated with a prescription without an indication were visits with a non-primary care provider, increasing visit length, and male gender. Sulfonamides and urinary anti-infectives were the antibiotics most commonly prescribed without an indication. Outpatient prescriptions without a documented indication continues to be the hole in appropriateness assessments. Other studies have reported up to 28% of outpatient prescriptions have no recent documented infectious indications. Further patient-level studies describing the missing indications are needed to help interpret current studies and guide future outpatient prescription appropriateness assessments.   

Feller and colleagues performed a retrospective cross-sectional study to quantify discharge antibiotics following hospitalizations and compared the relative contribution of post-discharge antibiotics versus inpatient antibiotics to overall antibiotic consumption during hospitalizations. The study included 1.7 million inpatient admissions across 122 US Veterans Affairs hospitals from 2014 to 2016. Eight hundred thousand admissions (47%) had an associated inpatient or post-discharge antibiotic prescription. Three hundred forty-thousand admissions (20%) had an associated post-discharge prescription. Of the 800 thousand admissions with an associated inpatient or post-discharge antibiotic, 58% were inpatient only, 39% were inpatient and post-discharge, and 3% were post-discharge only. The combined median inpatient and post-discharge days of therapy (DOTs) per 100 admissions were 535 (IQR 471, 601). Inpatient antibiotics accounted for 331 DOTs per 100 admissions (IQR 385, 368), and post-discharge antibiotics accounted for 210 DOTs/100 admissions (IQR 182, 240). Post-discharge antibiotics accounted for 39% of total antibiotic use related to hospital admissions. Furthermore, there was weak correlation between inpatient and post-discharge antibiotic use at the hospital level. Facilities with low inpatient antibiotic use may not necessarily have low post-discharge antibiotic use. The study highlights that the measurement of inpatient antibiotic use alone misses approximately 40% of antibiotic consumption related to hospitalizations. Discharge is an important timepoint for antibiotic stewardship programs to curtail potentially unnecessary antibiotic use. 


Ray MJ, Tallman GB, Bearden DT, Elman MR, McGregor JC. Antibiotic prescribing without documented indication in ambulatory care clinics: national cross sectional study. BMJ 2019 Dec 11;367:l6461. doi: 10.1136/bmj.l6461. 

Feller J, Lund BC, Perencevich EN, et al. Post-discharge oral antibiotic use among hospitalized patients across an integrated national healthcare network. Clin Microbiol Infect 2019 Oct 7. pii: S1198-743X(19)30501-4. doi: 10.1016/j.cmi.2019.09.016. 

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