Asymptomatic Bacteriuria in Adults, Screening -- Nonpregnant Adults


General

Grade: D

Specific Recommendations

The USPSTF recommends against screening for asymptomatic bacteriuria in nonpregnant adults.

Frequency of Service

No information available.

Risk Factor Information

The risk of developing asymptomatic bacteriuria varies by age, sex, and pregnancy status.6 Because of the location and length of the female urethra, women are predisposed to infections of the urinary tract, including asymptomatic bacteriuria.5 Physiologic changes in both pregnant and older women increase the risk of asymptomatic bacteriuria and a urinary tract infection.7, 11, 12 In general, men are at low risk of developing asymptomatic bacteriuria, although rates increase with older age.12 Persons with diabetes are also at increased risk of developing asymptomatic bacteriuria.4, 6


Clinical

Practice Considerations

Patient Population Under Consideration

This recommendation applies to adults 18 years and older and pregnant persons of any age without signs and symptoms of a urinary tract infection. It does not apply to persons who have chronic medical or urinary tract conditions, such as end-stage renal disease; have indwelling urinary catheters, urinary stents, or spinal cord injuries; are hospitalized; reside in an institution (eg, a nursing home); or who are transplant recipients.

Definition of Asymptomatic Bacteriuria

Asymptomatic bacteriuria occurs when the urinary tract is colonized with significant amounts of pathogenic bacteria, primarily from the gastrointestinal tract, in the absence of symptoms or signs of a urinary tract infection. The most common pathogen is Escherichia coli, although other bacteria such as Klebsiella, Proteus mirabilis, and group B streptococcus can be involved.4, 11

Assessment of Risk

The risk of developing asymptomatic bacteriuria varies by age, sex, and pregnancy status.6 Because of the location and length of the female urethra, women are predisposed to infections of the urinary tract, including asymptomatic bacteriuria.5 Physiologic changes in both pregnant and older women increase the risk of asymptomatic bacteriuria and a urinary tract infection.7, 11, 12 In general, men are at low risk of developing asymptomatic bacteriuria, although rates increase with older age.12 Persons with diabetes are also at increased risk of developing asymptomatic bacteriuria.4, 6

Screening Tests

Screening for asymptomatic bacteriuria during pregnancy is done with a urine culture at 12 to 16 weeks of gestation or at the first prenatal visit. Urine culture is currently recommended for screening in pregnancy and is the established method for diagnosis.2 A culture obtained using a midstream, clean-catch urine sample with greater than 100,000 colony-forming units (CFU) per milliliter of a single uropathogen is considered a positive test result.6 Greater than 10,000 CFU/mL of group B streptococcus is an indicator of vaginal colonization and is commonly used as the threshold for treatment of infection in pregnancy.13

Screening Intervals

In general, screening is performed once at the first prenatal visit per clinical guidelines. However, there is little evidence on the optimal timing and frequency of screening for asymptomatic bacteriuria in pregnancy.2

Treatment or Interventions

Pregnant persons with asymptomatic bacteriuria usually receive antibiotic therapy, based on urine culture results and follow-up monitoring. The choice of antibacterial regimen for treatment of asymptomatic bacteriuria during pregnancy is based on safety in pregnancy and patterns of antimicrobial resistance in the particular setting.6, 7

 

Update of Previous USPSTF Recommendations

In this update, the USPSTF continues to recommend screening for asymptomatic bacteriuria in pregnant persons with urine culture and recommends against screening in nonpregnant adults. The USPSTF changed the grade for pregnant persons from an “A” to a “B” based on the reduced applicability of the previous evidence that included outdated antibiotic treatment regimens and newer evidence that shows a significantly lower risk of pyelonephritis than found in previous reviews. In addition, there are newer concerns about antibiotic use, such as antimicrobial resistance and adverse changes to the microbiome (not addressed in current studies), leading to an increase in the magnitude of potential harms. These factors led the USPSTF to reduce assessments of certainty and magnitude of benefit, resulting in the change of grade.

Since 1996, the USPSTF has maintained an “A” recommendation for 1-time screening for asymptomatic bacteriuria with urine culture in pregnant persons between 12 and 16 weeks of gestation. The original 1996 recommendation was reaffirmed in 2004 and again in 2008.14-16 In 1996, the USPSTF found that there was insufficient evidence to recommend for or against screening in older adult women or women with diabetes and, in a separate recommendation, that screening was not recommended in other asymptomatic adults or older adults who reside in an institution.14 In 2004, these recommendations were combined into a single recommendation against screening, which was subsequently reaffirmed in 2008.15, 16


Rationale

Importance

Asymptomatic bacteriuria is defined as the presence of bacteria in the urine of a person without signs or symptoms of a urinary tract infection.1 Among the general adult population, women (across all ages) have the highest prevalence of asymptomatic bacteriuria, although rates increase with age among both men and women.2 The reported prevalence of asymptomatic bacteriuria ranges from 1% to 6% among premenopausal women to 22% among women older than 90 years.3, 4 Asymptomatic bacteriuria is present in an estimated 2% to 10% of pregnant women.5 The condition is rare in men.4, 6

During pregnancy, physiologic changes that affect the urinary tract increase the risk of asymptomatic bacteriuria and symptomatic urinary tract infections, including pyelonephritis (a urinary tract infection in which one or both kidneys become infected).7 Pyelonephritis is one of the most common nonobstetric reasons for hospitalization in pregnant women.8 Pyelonephritis is associated with perinatal complications including septicemia, respiratory distress, low birth weight, and spontaneous preterm birth.9

The presence of asymptomatic bacteriuria has not been shown to increase the risk of adverse health outcomes among nonpregnant persons.6, 10

 

USPSTF Assessment of Magnitude of Net Benefit

Pregnant Persons

The USPSTF concluded with moderate certainty that screening for and treatment of asymptomatic bacteriuria in pregnant persons has moderate net benefit in reducing perinatal complications (Table). There is adequate evidence that pyelonephritis in pregnancy is associated with negative maternal outcomes and that treatment of screen-detected asymptomatic bacteriuria can reduce the incidence of pyelonephritis in pregnant persons. However, evidence shows that the incidence of pyelonephritis among pregnant women with untreated asymptomatic bacteriuria has been low in recent decades, which may reduce the potential benefit from screening asymptomatic bacteriuria. When direct evidence is limited, absent, or restricted to select populations or clinical scenarios, the USPSTF may place conceptual upper or lower bounds on the magnitude of benefit or harms. Therefore, the USPSTF bounds the benefits of screening for asymptomatic bacteriuria in pregnant persons as no greater than moderate.

The USPSTF found inadequate direct evidence on the harms of screening for asymptomatic bacteriuria in pregnant persons, although these harms are thought to be no greater than small in magnitude. The USPSTF found adequate evidence of harms associated with treatment of asymptomatic bacteriuria, including adverse effects of antibiotic treatment. It also considered the potential effects of changes in the microbiome resulting from antibiotic use. Therefore, the USPSTF bounds the overall magnitude of harms of screening for asymptomatic bacteriuria in pregnant persons to be at least small.

Nonpregnant Adults

The USPSTF concludes with moderate certainty that screening for and treatment of asymptomatic bacteriuria in nonpregnant adults has no net benefit (Table). There is adequate evidence that treatment of screen-detected asymptomatic bacteriuria in nonpregnant adults has no benefit. Based on the harms associated with antibiotic use, the USPSTF found adequate evidence to bound the harms of treatment of screen-detected asymptomatic bacteriuria in nonpregnant adults as at least small.


Others

Recommendations of Others The Infectious Diseases Society of America recommends screening for asymptomatic bacteriuria in pregnant women and treatment for those who screen positive.40 The American College of Obstetricians and Gynecologists endorses the Infectious Diseases Society of America’s recommendations for screening for asymptomatic bacteriuria in pregnant women and treatment for those who screen positive. The Canadian Task Force on Preventive Health Care recommends screening in pregnant women with urine culture once during the first trimester, although this was issued as a “weak” recommendation and the quality of evidence was considered low.41 The American Academy of Pediatrics (AAP) has no specific recommendation to screen for asymptomatic bacteriuria in pregnant persons. However, the AAP recommends that clinicians treat pregnant persons and perform a test of cure if asymptomatic bacteriuria is found to be present on a urine culture. In 2008, the American Academy of Family Physicians recommended screening in pregnant women at 12 to 16 weeks of gestation or at the first prenatal visit, whichever comes first.42   The AAP, the American Academy of Family Physicians, and the United Kingdom’s National Institute for Health and Care Excellence all recommend against screening for and treatment of asymptomatic bacteriuria in nonpregnant adults.42-44 The American College of Obstetricians and Gynecologists recommends against screening for and treatment of asymptomatic bacteriuria in nonpregnant, premenopausal women.45


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