Perspective from Victoria Scott, MD
Disclosures: The authors report no relevant financial disclosures.

September 10, 2021
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Urine culture, empirical antibiotics most cost-effective UTI strategy

Perspective from Victoria Scott, MD
Disclosures: The authors report no relevant financial disclosures.

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In most cases, a urine culture combined with empirical antibiotics is the most cost-effective strategy for UTIs, according to researchers.

“We conducted this cost-effectiveness study because UTIs cost an estimated $1.6 billion dollars in the United States annually and is an area of health care recourse utilization with a potential for improvement,” Rui Wang, MD, from the department of women’s health at Hartford Hospital, in Connecticut, told Healio. “We evaluated the cost effectiveness of several different UTI testing and treatment strategies while accounting for the societal cost of antibiotic resistance.”

Wang R, et al. Am J Obstet Gynecol. 2021;doi:10.1016/j.ajog.2021.08.014.
Wang R, et al. Am J Obstet Gynecol. 2021;doi:10.1016/j.ajog.2021.08.014.

To determine the cost effectiveness of various UTI strategies, Wang and colleague Christine LaSala, MD, also from Hartford Hospital, designed a decision tree that would model four approaches to care. These included empirical antibiotics first, followed by culture-directed antibiotics if symptoms persist; initial urine culture, followed by culture-directed antibiotics; urine culture combined with empirical antibiotics, followed by culture-directed antibiotics if symptoms persist; and initial symptomatic treatment followed by culture-directed antibiotics if symptoms persist.

To address both patient- and society-level concerns, Wang and LaSala built three versions of their model with three different outcome measures: Quality-adjusted life-years (QALYs), symptom-free days and antibiotic courses given. The researchers modeled the societal cost of antibiotic resistance for each antibiotic regimen, with the probability of UTI and the level of antibiotic resistance analyzed from 0% to 100%. They additionally extended their model to account for patients who require a catheter for urine collection. Model parameter estimates were based on medical literature “whenever possible,” the researchers wrote.

The primary outcome was the incremental cost-effectiveness ratio (ICER), which the researchers defined as the difference between strategies in mean cost divided by the difference in mean QALYs. A strategy was defined as “dominated,” and thus rejected, if it was costlier and less effective than another strategy. Meanwhile, a strategy was “dominant” if it was less costly and more effective than any other strategy. A strategy was defined as cost-effective if it demonstrated an ICER less than the willingness-to-pay threshold of $150,000 per QALY, compared with another strategy. This threshold varied in the sensitivity analyses.

According to the researchers, using a base case assumption of 20% antibiotic resistance, urine culture at the same time as empirical antibiotics was the most cost-effective strategy that maximized symptom-free days. It demonstrated the lowest cost — $79.91 — and highest effectiveness — 24.44 quality adjusted life-days (QALDs). However, empirical antibiotics was the most cost-effective option when antibiotic resistance fell below 6%, whereas symptomatic treatment was the most cost-effective plan when resistance rose above 80%.

Meanwhile, symptomatic treatment first was always the best strategy, followed by urine culture first, to minimize antibiotic use, with a mean of 0.29 courses administered. Sensitivity analyses with other input parameters failed to impact the cost-effectiveness results. As the researchers extended their model to include an office visit for catheterized urine specimens, empirical antibiotics became the most cost-effective plan.

“The key finding is that, in most cases, obtaining urine culture with empirical antibiotics was the best strategy,” Wang said. “This had a greater than 80% chance of being the cost-effective strategy.

“Starting with only empirical antibiotics was cost-effective when the antibiotic resistance level is very low — less than 6% — while starting with only symptomatic treatment was cost-effective when the antibiotic resistance level was very high — greater than 80%,” she added. “Our model can be used to guide testing and management plans for patients presenting with sporadic UTIs or those with recurrent UTIs.”