29 August 2021
WHO recommendation on the method for diagnosing asymptomatic bacteriuria in pregnancy
Midstream urine culture is the recommended method for diagnosing asymptomatic bacteriuria (ASB) in pregnancy. In settings where urine culture is not available, on-site midstream urine Gram staining is recommended over the use of dipstick tests as the method for diagnosing ASB in pregnancy.
First published: December 2016
Updated: No update planned
Assessed as up-to-date: December 2016
Asymptomatic bacteriuria (ASB) is a common urinary tract condition that is associated with an increased risk of urinary tract infections (cystitis and pyelonephritis) in pregnant women. Escherichia coli is associated with up to 80% of isolates; other pathogens include Klebsiella species, Proteus mirabilis and group B streptococcus (GBS) (1).
Methods for diagnosing ASB include midstream urine culture (the gold standard), Gram stain and urine dipstick tests. A urine culture can take up to seven days to get a result, with the threshold for diagnosis usually defined as the presence of 105 colony-forming units (cfu)/mL of a single organism (2). The Gram stain test uses colour stains (crystal violet and safrinin O) to exaggerate and distinguish between Gram-positive (purple) and Gram-negative (red) organisms on a prepared glass slide. Urine dipsticks test for nitrites, which are not found in normal urine, and leucocytes, which are identified by a reaction with leucocyte esterase, to identify the presence of bacteria and pus in the urine, respectively.
ASB is associated with an increased risk of preterm birth; once detected it is, therefore, usually actively managed with antibiotics.
The ANC recommendations are intended to inform the development of relevant health-care policies and clinical protocols. These recommendations were developed in accordance with the methods described in the WHO handbook for guideline development (3). In summary, the process included: identification of priority questions and outcomes, retrieval of evidence, assessment and synthesis of the evidence, formulation of recommendations, and planning for the implementation, dissemination, impact evaluation and updating of the guideline.
The quality of the scientific evidence underpinning the recommendations was graded using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) (4) and Confidence in the Evidence from Reviews of Qualitative research (GRADE-CERQual) (5) approaches, for quantitative and qualitative evidence, respectively. Up-to-date systematic reviews were used to prepare evidence profiles for priority questions. The DECIDE (Developing and Evaluating Communication Strategies to support Informed Decisions and Practice based on Evidence) (6) framework, an evidence-to-decision tool that includes intervention effects, values, resources, equity, acceptability and feasibility criteria, was used to guide the formulation and approval of recommendations by the Guideline Development Group (GDG) – an international group of experts assembled for the purpose of developing this guideline – at three Technical Consultations between October 2015 and March 2016.
To ensure that each recommendation is correctly understood and applied in practice, the context of all context-specific recommendations is clearly stated within each recommendation, and the contributing experts provided additional remarks where needed.
In accordance with WHO guideline development standards, these recommendations will be reviewed and updated following the identification of new evidence, with major reviews and updates at least every five years.
Further information on procedures for developing this recommendation are available here.
For this recommendation, we aimed to answer the following question:
The evidence was derived from a test accuracy review of on-site urine tests conducted to support the ANC guideline (7). Four studies (1904 pregnant women) contributed data on urine Gram staining and eight studies (5690 pregnant women) contributed data on urine dipsticks. Most of the studies were conducted in LMICs. The average prevalence of ASB in the studies was 8%. A Gram stain was positive if one or more bacteria were detected per oilimmersed field, and a dipstick test was positive if it detected either nitrites or leucocytes. The reference standard used was urine culture with a threshold of 105 cfu/mL. However, the certainty of the evidence on the accuracy of both Gram stain tests and dipstick tests is very low, with pooled sensitivity and specificity of the Gram stain test estimated at 0.86 (95% CI: 0.80– 0.91) and 0.97 (95% CI: 0.93–0.99), respectively, and pooled sensitivity and specificity for urine dipsticks estimated at 0.73 (95% CI: 0.59–0.83) and 0.89 (95% CI: 0.79–0.94), respectively. A positive nitrite test alone on dipsticks was found to be less sensitive but more specific than when urine leucocytes were also considered.
Further information on evidence supporting this recommendation are available here.
The GDG identified these research priorities related to this recommendation
WHO recommendations on antenatal care for a positive pregnancy experience
Citation: WHO Reproductive Health Library. WHO recommendation on the method for diagnosing asymptomatic bacteriuria in pregnancy (December 2016). The WHO Reproductive Health Library; Geneva: World Health Organization.
Even though the limited number of trials included in this review found oral, intramuscular and intravenous iron to increase maternal haemoglobin values, the data were not sufficient to ascertain the clinical significance of these findings. Hence, this review does not recommend any treatment for iron-deficiency anaemia in pregnant women.Read Article
Vitamin D supplementation is not recommended for pregnant women to improve maternal and perinatal outcomes.Read Article
The full intravenous or intramuscular magnesium sulfate regimens are recommended for the prevention and treatment of eclampsia.Read Article