The U.S. Preventive Services Task Force (USPSTF) last addressed screening for asymptomatic bacteriuria in the 1996 Guide to Clinical Preventive Services, 2d ed., and made the following recommendations: all pregnant women should be screened for asymptomatic bacteriuria using urine culture at 12 to 16 weeks' gestation (A recommendation); and routine screening of pregnant women using leukocyte esterase or nitrite testing was not recommended because of poor test characteristics compared with urine culture (D recommendation).¹ There was insufficient evidence to recommend for or against routine screening of ambulatory elderly women or women with diabetes using leukocyte esterase or nitrite testing (C recommendation).¹ Routine screening for asymptomatic bacteriuria using leukocyte esterase or nitrite testing was not recommended for other asymptomatic persons, including institutionalized elderly persons (E recommendation), school-aged girls (E recommendation), and other children, adolescents, and adults (D recommendation).¹ Screening for asymptomatic bacteriuria with microscopy testing was not recommended (D recommendation).¹

Since the time these recommendations were released, the USPSTF criteria to rate the strength of the evidence have changed. Therefore, the recommendation statement that follows has been updated and revised based on the current USPSTF methodology and rating of the strength of the evidence.² Explanations of the current USPSTF ratings and of the strength of overall evidence are given in Tables 1 and 2, respectively. This recommendation statement and the brief update “Screening for Asymptomatic Bacteriuria,”³ are available through the USPSTF Web site (http://www.uspreventiveservicestaskforce.org), through the National Guideline Clearinghouse (http://www.guideline.gov), and in print through the AHRQ Publications Clearinghouse (telephone: 1-800-358-9295; e-mail:ahrqpubs@ahrq.gov).

Summary of Recommendations

The USPSTF strongly recommends screening for asymptomatic bacteriuria with urine culture in pregnant women at 12 to 16 weeks' gestation. A recommendation.

The USPSTF found good evidence that screening pregnant women for asymptomatic bacteriuria with urine culture significantly reduces symptomatic urinary tract infections, low birth weight, and preterm delivery. The benefits of screening and treatment substantially outweigh any potential harms.

The USPSTF recommends against routine screening for asymptomatic bacteriuria in men and nonpregnant women. D recommendation.

The USPSTF found fair evidence that screening men and nonpregnant women for asymptomatic bacteriuria is ineffective in improving clinical outcomes. In the absence of evidence of benefit, the potential harms associated with overuse of antibiotics are especially significant.

Clinical Considerations

• The screening tests used commonly in the primary care setting (i.e., dipstick urinanalysisanddirect microscopy) have poor positive and negative predictive values for detecting bacteriuria in asymptomatic persons. Urine culture is the gold standard for detecting asymptomatic bacteriuria but is expensive for routine screening in populations with a low prevalence of this condition. Results from one study done with a new enzymatic urine-screening test (Uriscreen) showed that the test has a sensitivity of 100 percent and a specificity of 81 percent.

• Good evidence exists that screening pregnant women for asymptomatic bacteriuria with urine culture (rather than urinalysis) significantly reduces symptomatic urinary tract infections, low birth weight, and preterm delivery. A specimen obtained at 12 to 16 weeks' gestation will detect approximately 80 percent of patients with asymptomatic bacteriuria. The optimal frequency of subsequent urine testing during pregnancy is uncertain.

• Good evidence exists that screening persons other than pregnant women for asymptomatic bacteriuria does not significantly improve clinical outcomes. Results from a study of women with diabetes who were treated for asymptomatic bacteriuria demonstrated no reduction in complications.⁴ Although there were short-term results in clearing bacteriuria with antimicrobial therapy, there was no decrease in the number of symptomatic episodes or hospitalizations over the long term. Furthermore, the high rate of recurrence of bacteriuria in those who were screened and treated resulted in a marked increase in the use of antimicrobial agents.