Variation in outpatient antibiotic prescribing in the United States

Abstract

Objective: To evaluate variation in outpatient antibiotic utilization among US commercial health plans and the implications of this variation for cost and quality.

Study design and methods: We measured antibiotic utilization rates among 229 US commercial health plans that participated in the 2005 Healthcare Effectiveness Data and Information Set. Rates were adjusted to account for health plan age and sex distribution. To estimate antibiotic costs, we multiplied utilization data for each drug class by national estimates of intraclass distribution of drugs, duration of therapy, and median average wholesale price.

Results: Antibiotic utilization rates varied markedly among plans, ranging from 0.64 antibiotic fills per member per year (PMPY) at the 5th percentile of plans to 1.08 fills PMPY at the 95th percentile, with a mean of 0.88 (SD +/- 0.15) antibiotic fills PMPY. US census region was the strongest predictor of antibiotic utilization. Antibiotic costs averaged $49 PMPY and ranged from $34 to $63 PMPY among plans at the 5th and 95th percentiles of cost, respectively. If a health plan with 250,000 members at the 90th percentile of antibiotic costs reduced its costs to the 25th percentile, annual drug cost savings would be approximately $4.1 million.

Conclusions: Antibiotic utilization varies substantially among commercial health plans and is not accounted for by differences in the age and sex distribution of plan members. Because reducing rates of antibiotic utilization is likely to lower costs and improve quality, high-utilizing plans may reap considerable rewards from investing in programs to reduce the overuse of antibiotics.

Figure 1. Health plans’ antibiotic utilization rate per-member-per-year, age 0–64

Per-member-per-year antibiotic utilization rates across health plans. Labels on the X-axis represent the mid-point of a range; for example, plans in the 0.90 category dispensed between 0.85 – 0.94 prescriptions PMPY.

Figure 2. Health plans’ antibiotic utilization rate per -member-per-year, by age and sex groups

For each age-sex category, the center dot represents the mean rate of antibiotic utilization across health plans. The bars show the range of antibiotic utilization rates for plans in the 5^th to 95^th percentile of utilization. Differences in mean utilization rates between adult females and males are likely due in part to differences in disease distribution. For example, urinary tract infections are a common source of antibiotic prescribing in women but not in men.