Evaluation of the Effectiveness of
Screening Asymptomatic Pregnant Women for Bacteriuria by a Combined Reagent
(Letter of intention)
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
- 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.
- Non-pregnant or puerperal women.
- Symptoms or upper or lower urinary tract infections.
- More than 20 weeks of gestational age.
- Consent forms not given.
- 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
- 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
- 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
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.
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Edited by Aldo Campana,