Cleansing the Perineum Before Obtaining Urine Samples?
Cleansing the Perineum Before Obtaining Urine Samples?
Vaillancourt S, McGillivray D. Zhang X, Kramer MS.
Pediatrics. 2007;119:e1288-e1293.
The authors report the first randomized trial in children to evaluate the value of cleaning the perineum with soap before collection of a midstream urine sample for analysis and culture.
This study enrolled children presenting to 1 emergency department (ED) over a 1-year period AND who had a urine analysis and/or culture ordered as part of his or her clinical care. The subjects were 2-18 years old, and all subjects were toilet trained.
The subjects were randomized by week -- any eligible child presenting to the ED was assigned the urine collection method that had been chosen at random for that week. On "cleaning" weeks, the subjects were provided with instruction on how to clean, how to obtain the sample, and the materials needed for cleaning. On "noncleaning" weeks, the subjects and parents were provided with instruction on how to obtain the sample. ED staff and providers were reminded of the type of week, both in person and by placards placed throughout the ED.
The investigators collected demographic and clinical information (circumcision status, renal problems, and antibiotic use) on the children by survey. The usual clinical care at the institution is to perform a urine analysis by dipstick in the ED. Urine samples testing "abnormal" by dipstick (any leukocyte esterase, nitrites, blood, protein, or glucose) are confirmed by microscopy. For the purpose of this study, a urine analysis was "positive" for concern of infection if the dipstick result revealed leukocyte esterase and/or nitrites or if there were 5 or more white blood cells per high-powered field on microscopic analysis of the urine.
All urine analyses positive for concern of bacterial infection were cultured. The authors enrolled 350 subjects (60% female). More than two thirds of the males were not circumcised. Seven percent of the subjects had urinary tract infections (n = 23), and Escherichia coli caused 83% of those. Almost all positive culture specimens were in female subjects. Fifty-five subjects had contaminated urine cultures, evidenced by < 1000 colony-forming units/mL or mixed cultures.
The contamination rate was much lower in the cleaning group at 7.8% compared to 23.9% in the non-cleaning group (relative risk 0.37, 95% CI 0.19-0.57). In addition, the cleaning group was less likely to have a "positive" urine analysis at 20.6% compared to 36.8% in the noncleaning group. The positive predictive value (the proportion of "positive" urine analyses that truly indicated infection) was higher in the cleaning group. Finally, when the authors stratified by age, cleaning was even more effective in older children (6-18 years old).
The authors conclude that cleansing the perineum before obtaining urine samples reduces the rate of positive urine analyses and contaminated urine cultures.
There are 2 very important take-home points here. First, this study drives home a point that most might not find surprising -- that cleaning the perineum leads to fewer contaminated urine cultures. However, the second point -- that cleaning leads to lower rates of abnormal urine analyses -- has an even broader implication. Since many decisions to treat or not treat potential urinary tract infections (UTIs) must be made at the point of care (eg, any ED, or any private practice on a Friday afternoon, as examples), the potential impact of poor cleansing on the number of children treated for UTI based on urine analyses is substantial, raising the number of "abnormal" urine analyses in this study by 78%. So, take the time to have someone explain the need for a good specimen to the parents (or older patient), and make sure you provide the materials needed for adequate cleansing.
Abstract
Vaillancourt S, McGillivray D. Zhang X, Kramer MS.
Pediatrics. 2007;119:e1288-e1293.
The authors report the first randomized trial in children to evaluate the value of cleaning the perineum with soap before collection of a midstream urine sample for analysis and culture.
This study enrolled children presenting to 1 emergency department (ED) over a 1-year period AND who had a urine analysis and/or culture ordered as part of his or her clinical care. The subjects were 2-18 years old, and all subjects were toilet trained.
The subjects were randomized by week -- any eligible child presenting to the ED was assigned the urine collection method that had been chosen at random for that week. On "cleaning" weeks, the subjects were provided with instruction on how to clean, how to obtain the sample, and the materials needed for cleaning. On "noncleaning" weeks, the subjects and parents were provided with instruction on how to obtain the sample. ED staff and providers were reminded of the type of week, both in person and by placards placed throughout the ED.
The investigators collected demographic and clinical information (circumcision status, renal problems, and antibiotic use) on the children by survey. The usual clinical care at the institution is to perform a urine analysis by dipstick in the ED. Urine samples testing "abnormal" by dipstick (any leukocyte esterase, nitrites, blood, protein, or glucose) are confirmed by microscopy. For the purpose of this study, a urine analysis was "positive" for concern of infection if the dipstick result revealed leukocyte esterase and/or nitrites or if there were 5 or more white blood cells per high-powered field on microscopic analysis of the urine.
All urine analyses positive for concern of bacterial infection were cultured. The authors enrolled 350 subjects (60% female). More than two thirds of the males were not circumcised. Seven percent of the subjects had urinary tract infections (n = 23), and Escherichia coli caused 83% of those. Almost all positive culture specimens were in female subjects. Fifty-five subjects had contaminated urine cultures, evidenced by < 1000 colony-forming units/mL or mixed cultures.
The contamination rate was much lower in the cleaning group at 7.8% compared to 23.9% in the non-cleaning group (relative risk 0.37, 95% CI 0.19-0.57). In addition, the cleaning group was less likely to have a "positive" urine analysis at 20.6% compared to 36.8% in the noncleaning group. The positive predictive value (the proportion of "positive" urine analyses that truly indicated infection) was higher in the cleaning group. Finally, when the authors stratified by age, cleaning was even more effective in older children (6-18 years old).
The authors conclude that cleansing the perineum before obtaining urine samples reduces the rate of positive urine analyses and contaminated urine cultures.
There are 2 very important take-home points here. First, this study drives home a point that most might not find surprising -- that cleaning the perineum leads to fewer contaminated urine cultures. However, the second point -- that cleaning leads to lower rates of abnormal urine analyses -- has an even broader implication. Since many decisions to treat or not treat potential urinary tract infections (UTIs) must be made at the point of care (eg, any ED, or any private practice on a Friday afternoon, as examples), the potential impact of poor cleansing on the number of children treated for UTI based on urine analyses is substantial, raising the number of "abnormal" urine analyses in this study by 78%. So, take the time to have someone explain the need for a good specimen to the parents (or older patient), and make sure you provide the materials needed for adequate cleansing.
Abstract