Preoperative Asymptomatic Bacteriuria Screening and Treatment Not Necessarily Tied to Better Postoperative Outcomes

Although many clinicians hold that the presence of asymptomatic bacteriuria (ASB) in preoperative urine cultures is a risk marker for poor patient outcomes, a new study has found that screening for and treating ASB does not necessarily improve postoperative results.

Investigators from the VA Boston Healthcare System, Boston University School of Medicine, and Harvard Medical School conducted a national cohort study, published in JAMA Surgery, to examine the association between preoperative ASB—and antimicrobial therapy for patients with positive urine cultures—and postoperative infections such as surgical-site infection (SSI) and urinary tract infection (UTI).

A total of 755 out of 17,749 preoperative urine cultures tested positive, with 617 (81.7%) classified as preoperative ASB.

“Among the 617 patients with ASB, 15 (2.4%) had an SSI compared with 268 (1.6%) of the 16,994 patients without ASB,” Jaime Gallegos Salazar, MD; William O’Brien, MS; Judith M. Strymish, MD; and colleagues reported. “After adjusting for age, ASA class, smoking status, race/ethnicity, sex, and diabetes status, no statistically significant difference in rates of SSI was identified in patients with or without ASB (adjusted odds ratio [aOR], 1.58; 95% CI, 0.93-2.70; P = .08).”

Out of 13,336 orthopedic and vascular procedures, 210 UTIs were reported. Of these, 14 patients (3.3%; n = 423) had ASB, and 196 patients (1.5%; n = 12,913) did not (aOR, 1.42; 95% CI, 0.80-2.49; P = .22).

“The findings of this study suggest that receipt of antimicrobial therapy with activity against ASB organisms identified in preoperative urine cultures was not associated with reductions in the risk for postoperative infections, including UTI and SSI; such findings suggest there is evidence for discontinuing the practice of screening and treatment for preoperative ASB,” investigators wrote.

“Of importance, active antimicrobial therapy directed toward the asymptomatic uropathogen was not associated with improvement in any measurable postoperative clinical outcome; the rates of manually determined SSI, UTI, and positive wound and urine culture results were the same in patients who were treated and in those who were untreated,” they continued. “These data, therefore, suggest that there is no clinical utility to preoperative screening of urine cultures for cardiac, orthopedic, and vascular surgical procedures.”

Although the study focused on 68,265 predominantly male veterans who underwent surgical procedures in facilities within the US Department of Veterans Affairs (VA) health care system, the findings could have universal implications, namely the disimplementation of routine preoperative urine screenings, according to Barbara Wells Trautner, MD, PhD, who wrote an accompanying invited commentary on the study.

“Surgeons and infectious disease doctors alike have begun to question the value of routine preoperative screening for ASB,” Dr. Trautner told Contagion® in an interview. “But until this study was published, we had very little evidence on this clinical question. The results of this VA-wide observational study demonstrate clearly that screening for and treatment of preoperative ASB do not lead to improve clinical outcomes for surgical patients.”

The bigger picture here is antibiotic stewardship and preventing antimicrobial resistance.

“Decreased urine testing in asymptomatic patients means decreased use of unnecessary antibiotics down the line,” Dr. Trautner said. “Reducing the practice of preoperative testing for ASB will be a win for antibiotics stewardship and thus help prevent antimicrobial resistance.”

Dr. Trautner addressed this topic in a video interview with Contagion® over the summer, saying that screening for and treatment of ASB in most groups of patients is not helpful and may even be harmful.

She commented further this week.

“Patients with ASB often have more comorbidities than patients without ASB,” Dr. Trautner said. “Multiple studies have thus found an association between ASB and risk of poor clinical outcomes, such as SSI. However, the findings from this study strongly support the hypothesis that ASB is not in the causal pathway for SSI, as treatment of ASB did not decrease the risk of SSI or UTI.”