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8th Postgraduate Course for Training in Reproductive Medicine and Reproductive Biology

Evaluation of the Effectiveness of Screening Asymptomatic Pregnant Women for Bacteriuria by a Combined Reagent Strip

(Letter of intention)

E.J. Abalos
Centro Rosarino de Estudios Perinatales (C.R.E.P.), Rosario, Argentina
Maternidad Martin, Rosario, Argentina


The objective of this research is to determine the clinical effectiveness of a rapid office test (Tiras Reactivas Bayer Para Urianalisis) as screening method for predicting asymptomatic bacteriuria in pregnant women, confirmed by urinary culture.


Type of study: Prospective case series.

Study population: Asymptomatic pregnant women in their first antenatal visit.

Inclusion criteria:
  • Pregnant women in their first antenatal visit
  • Without symptoms of upper or lower urinary tract disorders
  • Without antibiotic treatment (for any cause)
  • Less than 20 weeks of gestational age.
Exclusion criteria:
  • Non-pregnant or puerperal women.
  • Symptoms or upper or lower urinary tract infections.
  • More than 20 weeks of gestational age.
  • Consent forms not given.
Study procedures:
  • In their first antenatal visit, patients will be informed about the study, and consent form will be requested.
  • Patients that give the consent form will be instructed by a trained nurse for collecting a clean voided midstream sample of urine (first sample of the morning). Samples will be collected in consecutive numerated sterile recipients.
  • One aliquot of urine will be extracted from this recipient by a sterile pipette and collected in a second numerated receiver.
  • The nurse will perform there the screening test (Tiras Reactivas Bayer Para Urianalisis, Bayer, Arg.) according to the manufacturer’s instructions. Strips contain several pads that react to the following: glucose, billirubin, ketones, blood, pH, proteins, urobylinogen, nitrites and leukocyte esterase.
  • Nurse will read Results at 60 seconds.
  • Results (defined as positive, negative and indeterminate for each of its components) will be registered in a formulary ad-hoc.
  • The first aliquot will be referred to Bacteriology Laboratory within 2 hours for performing formal urine culture. Samples will be processed for quantitative culture on sheep-blood agar plates by trained staff. The plates will be incubated and read at 12, 24 and 72 hours. Antibiotic sensitivities will be determined.
  • Cultures will be defined as positive if shows a growth of a single uropathogen of 100 000 colony forming unit (CFU) /ml or more. Negative if shows no growth of bacteria and contaminated there is a mixed culture of any density or a pure culture of less than 100 000 CFU/ml.
  • Patients with contaminated cultures will be asked in the second visit for another sample of urine that will be processed in the same way.
  • Results of cultures will be registered in a formulary ad-hoc.
  • Patients, physicians and laboratory staff will be blinded about reagent strip results.
  • Culture results will be available for physicians and patients.

Outcome measures: Presence of bacteriuria confirmed by formal urine culture.

Statistical analysis: Sensitivity, Specificity, Predictive Values and Likelihood ratios for positive and negative test results will be estimated for each component and all possible combinations.

Sample size: For a population of 4000 deliveries a year, with a prevalence of 6% of asymptomatic bacteriuria, sample size calculated for a 95% confidence interval, with an error of 10% was 1600 patients (Epi Info. ver. 6.0, Statcalc: sample size for population studies).

Timetable: Assuming that 80% of our patients have prenatal care at the moment of delivery, and from them, 50% have their first control before 20 weeks of gestation, time estimated for this research reach 18 consecutive month.


This study does not have problems of feasibility, while formal cultures are a routine practice for all patients at their first prenatal visit.


No conflict of ethics known.