Association Between Clean-Catch and Catheterized Urine Samples in Obese Females

Urine samples are part of urogynecologic evaluation, but limited data exist on the optimal urine collection technique in obese female patients.

The objective of this study was to compare dipstick urinalysis and culture results obtained from obese females via midstream clean-catch and straight catheterization.

We performed a prospective cross-sectional study of obese females aged ≥18 years with a body mass index (BMI) ≥30 presenting for urogynecologic consult. Women with symptoms of acute urinary tract infection were excluded. Midstream clean-catch and straight catheterization urine samples were collected from all participants. Dipstick urinalysis and urine cultures were performed on both specimens to compare results using contingency tables, Cohen's Kappa, and logistic regression.

Two hundred one patients were included with a mean age of 59.61±13.42 years and a median (IQR) BMI of 35.8 (33.0-40.3). Agreement between collection methods was moderate for nitrites (κ=0.65). There was weak agreement between the collection methods for blood, leukocytes, and bacteria (all κ<0.60). Nearly half of the midstream clean-catch cultures were contaminated with ≥3 mixed bacteria versus catheterized specimens (42.3% vs 3.5% respectively, P <0.001). Culture contamination was not more likely with increasing BMI for clean-catch or catheterized specimens (odds ratio [OR]=1.0, 95% CI, 0.96-1.10 and OR=1.0, 95% CI, 0.94-1.16, respectively). Culture contamination was not associated with age by decade in clean-catch or catheterized specimens (OR=1.0, 95% CI, 0.83-1.27 and OR=1.3, 95% CI, 0.72-2.40, respectively).

Agreement between midstream clean-catch and catheterized specimens among obese female patients is poor. Midstream clean-catch urine cultures were more likely to be contaminated, though increasing BMI does not appear to influence the odds of contamination among obese patients.