By Jake Scott, MD
Clinical Assistant Professor, Infectious Diseases and Geographic Medicine, Stanford University School of Medicine; Antimicrobial Stewardship Program Medical Director, Stanford Health Care Tri-Valley
SYNOPSIS: In this retrospective cohort study of patients at United States Department of Veterans Affairs medical centers who underwent major elective, noncardiac, nonurological surgeries, preoperative urine culture testing was not associated with a significant decrease in postoperative incidence of urinary tract infections or surgical site infections.
SOURCE: O’Brien WJ, Schweizer ML, Strymish J, et al. Propensity score-weighted analysis of postoperative infection in patients with and without preoperative urine culture. JAMA Netw Open 2024;7:e240900.
O’Brien and colleagues conducted a retrospective cohort study of patients at United States Department of Veterans Affairs (VA) medical centers who underwent major elective, noncardiac, nonurological surgeries to assess the association between performing preoperative urine culture and postoperative infection.1 Patient data from Jan. 1, 2017, to Dec. 31, 2019, were reviewed from any of the 112 VA medical centers that perform surgical procedures. Patients were excluded from the analysis if they had undergone genitourinary procedures (since preoperative urine testing is generally recommended for these patients), if they had a fever or diagnosis of a urinary tract infection (UTI) within 30 days of surgery, or if they had a history of a cystectomy. Data were obtained from the VA Surgical Quality Improvement Program (VASQIP), which included details on the surgical procedures, patient baseline characteristics, and 30-day postoperative outcomes, and from the Clinical Data Warehouse (CDW) Laboratory Microbiology database.
Two outcomes were assessed in the 30-day postoperative period: UTI and surgical site infection (SSI), which were defined using National Healthcare Safety Network criteria. To balance baseline characteristics between patients who did and did not have preoperative urine cultures performed, and to reduce confounding by indication, propensity score estimations were made using inverse probability of treatment weighting (IPTW) and machine learning.
The analysis included 250,389 VA patients who underwent 288,858 surgical procedures. The majority of surgical procedures (88.9%) were received by male patients; 67.2% were received by white patients, 16.6% by Black patients, and 6.7% by patients who identified as other race or ethnicity. Patients 65 years of age or older received 48.9% of surgical procedures. Before IPTW, patients who had a preoperative urine culture performed were more likely to be older, have a higher American Society of Anesthesiologists (ASA) Physical Status Classification, receive antibiotics within 30 days before surgery, have a history of UTI, and have preoperative urinary retention. Patients in both groups were well balanced after applying IPTW.
Preoperative urine culture was performed within 30 days for 10.5% of procedures (30,384 of 288,858). In the balanced study population, performing a preoperative urine culture was not associated with a significantly decreased risk of UTI or SSI. Among surgical procedures for which a preoperative urine culture was performed, 0.6% (173 of 30,384) were followed by a postoperative UTI, as compared with 0.4% (1,012 of 8,474) of procedures without preoperative urine culture testing (adjusted odds ratio [AOR], 1.18; 95% confidence interval [CI], 0.98 to 1.40).
SSIs were reported following 1.3% (400 of 30,384) of surgical procedures for which preoperative urine culture was performed, as compared with 1.5% (3,837 of 258,474) of those without preoperative urine culture testing (AOR, 0.99; 95% CI, 0.90 to 1.10). In a subgroup analysis of patients who underwent orthopedic surgery and neurosurgery, no significant difference was found in incidence of postoperative UTI (AOR, 1.27; 95% CI, 0.97 to 1.65) or SSI (AOR, 0.93; 95% CI, 0.76 to 1.12) between procedures with and without preoperative urine culture testing, respectively.
COMMENTARY
Asymptomatic bacteriuria (ASB), which is defined as the isolation of a significant colony count of bacteria from a urine specimen in an individual without signs or symptoms of a UTI, is relatively common.2,3 With the exception of pregnant patients and patients undergoing urological procedures expected to result in mucosal bleeding, guidelines recommend against screening for and treating ASB.4,5 A meta-analysis of nine trials that evaluated the impact of the treatment of ASB found that treatment is not associated with a reduction in the frequency of symptomatic UTI or the risk of other adverse outcomes.6 In fact, the treatment of ASB is more likely to cause significant harm than provide any benefit, as it has been found to lead to higher rates of adverse events (relative risk, 3.77; 95% CI, 1.40 to 10.15), the emergence of antibiotic resistance in subsequently isolated organisms, higher healthcare costs, increased hospital length of stay, and various other untoward consequences that result from the overuse of antibiotics, including likely higher rates of Clostridioides difficile infection.6-10
Despite substantial evidence and clear guideline recommendations, dissuading clinicians from treating ASB remains a common challenge. In one study of nearly 15,000 patients with a positive urine culture, 28.4% (4,134) of patients had ASB and 76.8% (3,175) of these patients received antibiotics. To effectively curb the overuse of antibiotics, it is important to employ both antibiotic stewardship measures to prevent or reduce the use of inappropriate antibiotics as well as diagnostic stewardship measures to limit inappropriate testing and guide appropriate clinical decision-making, which may be more effective.11
This analysis by O’Brien and colleagues of nearly 300,000 surgical procedures provides further evidence that routine preoperative urine cultures are not indicated for asymptomatic patients prior to nonurological procedures and emphasizes the importance of diagnostic stewardship.
REFERENCES
- O’Brien WJ, Schweizer ML, Strymish J, et al. Propensity score-weighted analysis of postoperative infection in patients with and without preoperative urine culture. JAMA Netw Open 2024;7:e240900.
- Nicolle LE. Asymptomatic bacteriuria. Curr Opin Infect Dis 2014;27:90-96.
- Juthani-Mehta M. Asymptomatic bacteriuria and urinary tract infection in older adults. Clin Geriatr Med 2007;23:585-594, vii.
- Nicolle LE, Gupta K, Bradley SF, et al. Clinical Practice Guideline for the Management of Asymptomatic Bacteriuria: 2019 Update by the Infectious Diseases Society of America. Clin Infect Dis 2019;68:e83-e110.
- US Preventive Services Task Force; Owens DK, Davidson KW, Krist AH, et al. Screening for asymptomatic bacteriuria in adults: US Preventive Services Task Force Recommendation Statement. JAMA 2019;322:1188-1194.
- Zalmanovici Trestioreanu A, Lador A, Sauerbrun-Cutler MT, Leibovici L. Antibiotics for asymptomatic bacteriuria. Cochrane Database Syst Rev 2015;4:CD009534.
- Cai T, Nesi G, Mazzoli S, et al. Asymptomatic bacteriuria treatment is associated with a higher prevalence of antibiotic resistant strains in women with urinary tract infections. Clin Infect Dis 2015;61:1655-1661.
- Harris AHS, Bowe T, Kamal RN, et al. Frequency and costs of low-value preoperative tests for patients undergoing low-risk procedures in the Veterans Health Administration. Perioper Med (Lond) 2022;11:33.
- Petty LA, Vaughn VM, Flanders SA, et al. Risk factors and outcomes associated with treatment of asymptomatic bacteriuria in hospitalized patients. JAMA Intern Med 2019;179:1519-1527.
- Spivak ES, Burk M, Zhang R, et al. Management of bacteriuria in Veterans Affairs hospitals. Clin Infect Dis 2017;65:910-917.
- Vaughn VM, Gupta A, Petty LA, et al. A statewide quality initiative to reduce unnecessary antibiotic treatment of asymptomatic bacteriuria. JAMA Intern Med 2023;183:933-941.
