CTF Structured Abstract: Asymptomatic Bacteriuria

Canadian Task Force on Preventive Health Care

Structured Abstract

Screening for Asymptomatic Bacteriuria in Pregnancy

Prepared by Lindsay E. Nicolle, MD, Department of Medicine, University of Manitoba

These recommendations were finalized by the Task Force in October 1993

Objective
Burden of Suffering
Options
Outcomes

Evidence
Values
Benefits, Harms, and Costs
Recommendations

Validation
Sponsors
Selected References

Objective

To make recommendations for screening women who are pregnant for bacteriuria in Canada.

Burden of Suffering

The prevalence of asymptomatic bacteriuria in pregnancy varies from 4-7% and is similar to that observed in non-pregnant women. The prevalence is higher among individuals in lower socioeconomic classes, and those with a past history of asymptomatic urinary infection. There is a high incidence of pyelonephritis occurring later in pregnancy in women with asymptomatic bacteriuria identified and not treated early in pregnancy. 13% of untreated women with asymptomatic bacteriuria developed pyelonephritis, compared with 0.4% of those with negative screening cultures. Women with urinary infection (UTI) associated pregnancy have been shown to have higher fetal mortality rates, and increased risk of low birth weight and prematurity.

Options

Screening options include bacterial culture of urine, urinalysis, and dipslide method. The treatment strategy for women who have bacteriuria is antibiotics.

Outcomes

Sensitivities and specificities of the tests, development of pyelonephritis in pregnant women, cure rates, intra-uterine growth retardation, low birth weight, stillbirth, and premature delivery of the infant. Costs were mentioned briefly.

Evidence

MEDLINE was searched to 1993 using the keywords urinary tract infections, pregnancy, human and case reports.

Recommendations were graded as:

A Good evidence to support the recommendation that the condition be specifically considered in a PHE.

B Fair evidence to support the recommendation that the condition be specifically considered in a PHE.

C Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds.

D Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

E Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

Quality of evidence was rated according to 5 levels:

I Evidence from at least 1 properly randomized controlled trial (RCT).

II-1 Evidence from well-designed controlled trials without randomization.

II-2 Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group.

II-3 Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here.

III Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees.

Values

The 13-member Task Force of experts in family medicine, geriatric medicine, pediatrics, psychiatry and epidemiology used an evidence-based method for evaluating the effectiveness of preventive health care interventions. Recommendations were not based on cost-effectiveness of options. Patient preferences were not discussed.

Background papers providing critical appraisal of the evidence and tentative recommendations prepared by the chapter author were pre-circulated to the members. Evidence for this topic was presented and deliberated upon in 1- to 2-day meetings, 2 to 3 times per year from January 1993 to June 1993. Consensus was reached on final recommendations.

Benefits, Harms, and Costs

The gold standard for screening for asymptomatic bacteriuria is urine culture from women early in their pregnancy (12 to 16 weeks). Nonculture methods such as urinalysis and leukocyte-esterase dipstick are not reliable. Compared with semi-quantitative culture, the dipslide method is less costly and less prone to error. For women with asymptomatic bacteriuria a second sample is required for determination in the laboratory using quantitative culture for confirmation of bacteriuria, identification of organisms, and antimicrobial susceptibility testing. Optimal time for screening is at 12 to 16 weeks' gestation; this will identify 80% of women who will ultimately have asymptomatic bacteriuria during pregnancy.

All but 1 study showed that women who tested positive for bacteriuria and were treated had a decrease in the incidence of pyelonephritis from a range of 20% to 30% to a range of 2% to 4%. 1 study showed that screening with a single urine specimen in early pregnancy was cost effective as long as the population prevalence of bacteriuria was > 2%.

A meta-analysis of 8 studies showed that treatment of asymptomatic bacteriuria reduced the risk for low birth weight (relative risk 0.56, 95% CI 0.43 to 0.73); this antibiotic treatment might, however, be associated with subclinical chorioamnionitis rather than bacteriuria. Other pregnancy related outcomes have insufficient evidence for recommendations to be made.

Recommendations

Recommendation grade [A, B, C, D, E] and level of evidence [I, II-1, II-2, II-3, III] are indicated after each recommendation. Citations in support of individual recommendations are identified in the guideline text.

Good evidence exists to include in the PHE of pregnant women, at 12 to 16 weeks' gestation, one time culture method screening for asymptomatic bacteriuria. [A, I, II-1]

Validation

This report was externally peer reviewed. In 1989, the U.S. Preventive Services Task Force recommended that pregnant women be tested periodically with urine cultures for asymptomatic bacteriuria. Frequency of testing was left up to the individual clinician to decide.

Selected References

Source Document

Nicolle L.E. Screening for asymptomatic bacteriuria in pregnancy. In: Canadian Guide to Clinical Preventive Health Care. Ottawa: Health Canada, 1994; 100-6.

Link to Full Text of this review

Link to Summary Table of Recommendations of this review

Link to Selected References list of this review

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A	Good evidence to support the recommendation that the condition be specifically considered in a PHE.
B	Fair evidence to support the recommendation that the condition be specifically considered in a PHE.
C	Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds.
D	Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.
E	Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

I	Evidence from at least 1 properly randomized controlled trial (RCT).
II-1	Evidence from well-designed controlled trials without randomization.
II-2	Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group.
II-3	Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here.
III	Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees.