Contamination rates of three urine-sampling methods to assess bacteriuria in pregnant women.
OBJECTIVE
To estimate and compare contamination rates of three different urine-sampling methods in pregnant women to assess bacteriuria.


METHODS
In this cross-sectional study, 113 pregnant women collected three different midstream urine samples consecutively: morning (first void); midstream (void without further instructions); and clean-catch sample (void after cleaning). The following end points were considered contaminants: epithelial cells, Gram-positive rods or mixed bacteria in the Gram stain, and mixed growth or skin flora in the urine culture. Intraindividual variability in contaminants was quantified with Fleiss-Cohen's weighted κ statistic. Differences between samples were assessed using generalized estimating equations.


RESULTS
Mainly low numbers of Gram-positive rods were more likely to be present in Gram stains of midstream samples compared with clean-catch samples (77.7% compared with 66.7%, P=.022). Morning samples showed more mixed growth compared with midstream samples (6.2% compared with 0.9%, P=.050). No consistency in quantity of contaminants was found in midstream samples compared with morning and clean-catch samples. No differences were found between the other end points in all three urine samples (P>.05). The study could detect an odds ratios of 2.0 for differences in urine-sampling methods with 80% power and 5% significance for most end points.


CONCLUSIONS
In pregnant women, the contamination rate of midstream samples is comparable with the contamination rates of morning and clean-catch samples. The quantity of contaminants varied among the three samples collected by one woman. These results show that more complex, unpractical, and time-consuming morning and clean-catch samples are not superior. Therefore, we recommend a midstream sample to assess bacteriuria in pregnant women.


METHODS
II.
Departments of Epidemiology and Obstetrics and Gynecology, University of Groningen, University Medical Center Groningen, Groningen, and the Departments of Medical Microbiology and Internal Medicine, Division Infectious Disease, Academic Medical Center, Amsterdam, The Netherlands.
Caroline
C
Schneeberger
Edwin R
ER
van den Heuvel
Jan Jaap H M
JJHM
Erwich
Ronald P
RP
Stolk
Caroline E
CE
Visser
Suzanne E
SE
Geerlings
D000328:Adult; D001437:Bacteriuria / Q000175:diagnosis* / Q000382:microbiology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis* / Q000382:microbiology*; D013048:Specimen Handling / Q000379:methods*; D016482:Urinalysis / Q000379:methods*; D055815:Young Adult