A comparative study on bacterial cultures of urine samples obtained by clean-void technique versus urethral catheterization

Evaluation of bladder stimulation as a non-invasive technique for urine collection to diagnose urinary tract infection in infants under 6 months: a randomized multicenter study ("EE-Sti.Ve.N")

Background

Febrile urinary tract infection (UTI) is common in infants and needs to be diagnosed quickly. However, the symptoms are non-specific, and diagnosis can only be confirmed after high quality urinalysis. The American Academy of Pediatrics recommends suprapubic aspiration (1–9% contamination) and urinary catheterization (8–14% contamination) for urine collection but both these procedures are invasive. Recent studies have shown a new non-invasive method of collecting urine, bladder stimulation, to be quick and safe. However, few data about bacterial contamination rates have been published for this technique. We hypothesize that the contamination rate of urine collection by bladder stimulation to diagnose febrile UTI in infants under 6 months is equivalent to that of urinary catheterization.

Methods/design

This trial aims to assess equivalence in terms of bacterial contamination of urinary samples collected by urinary catheterization and bladder stimulation to diagnose UTI. Seven hundred seventy infants under 6 months presenting with unexplained fever in one of four Pediatric Emergency Departments in France will be enrolled. Each child will be randomized into a bladder stimulation or urinary catheterization group. The primary endpoints will be the validity of the urine sample assessed by the presence of contamination on bacterial culture.

Conclusion

A high recruitment rate is achievable due to the high prevalence of suspected UTIs in infants. The medical risk is the same as that for routine clinical care as we analyze patients with isolated fever.

If our hypothesis holds true and the rate of urine contamination collected by bladder stimulation is acceptable, the infants included in the study will have benefited from a non-invasive and reliable means of collecting urine.

Trial registration

ClinicalTrials.gov, NCT03801213. Registered on 11 January 2019.

The Diagnosis of Urinary Tract infection in Young children (DUTY): a diagnostic prospective observational study to derive and validate a clinical algorithm for the diagnosis of urinary tract infection in children presenting to primary care with an acute illness

BACKGROUND

It is not clear which young children presenting acutely unwell to primary care should be investigated for urinary tract infection (UTI) and whether or not dipstick testing should be used to inform antibiotic treatment.

OBJECTIVES

To develop algorithms to accurately identify pre-school children in whom urine should be obtained; assess whether or not dipstick urinalysis provides additional diagnostic information; and model algorithm cost-effectiveness.

DESIGN

Multicentre, prospective diagnostic cohort study.

SETTING AND PARTICIPANTS

Children < 5 years old presenting to primary care with an acute illness and/or new urinary symptoms.

METHODS

One hundred and seven clinical characteristics (index tests) were recorded from the child's past medical history, symptoms, physical examination signs and urine dipstick test. Prior to dipstick results clinician opinion of UTI likelihood ('clinical diagnosis') and urine sampling and treatment intentions ('clinical judgement') were recorded. All index tests were measured blind to the reference standard, defined as a pure or predominant uropathogen cultured at ≥ 10(5) colony-forming units (CFU)/ml in a single research laboratory. Urine was collected by clean catch (preferred) or nappy pad. Index tests were sequentially evaluated in two groups, stratified by urine collection method: parent-reported symptoms with clinician-reported signs, and urine dipstick results. Diagnostic accuracy was quantified using area under receiver operating characteristic curve (AUROC) with 95% confidence interval (CI) and bootstrap-validated AUROC, and compared with the 'clinician diagnosis' AUROC. Decision-analytic models were used to identify optimal urine sampling strategy compared with 'clinical judgement'.

RESULTS

A total of 7163 children were recruited, of whom 50% were female and 49% were < 2 years old. Culture results were available for 5017 (70%); 2740 children provided clean-catch samples, 94% of whom were ≥ 2 years old, with 2.2% meeting the UTI definition. Among these, 'clinical diagnosis' correctly identified 46.6% of positive cultures, with 94.7% specificity and an AUROC of 0.77 (95% CI 0.71 to 0.83). Four symptoms, three signs and three dipstick results were independently associated with UTI with an AUROC (95% CI; bootstrap-validated AUROC) of 0.89 (0.85 to 0.95; validated 0.88) for symptoms and signs, increasing to 0.93 (0.90 to 0.97; validated 0.90) with dipstick results. Nappy pad samples were provided from the other 2277 children, of whom 82% were < 2 years old and 1.3% met the UTI definition. 'Clinical diagnosis' correctly identified 13.3% positive cultures, with 98.5% specificity and an AUROC of 0.63 (95% CI 0.53 to 0.72). Four symptoms and two dipstick results were independently associated with UTI, with an AUROC of 0.81 (0.72 to 0.90; validated 0.78) for symptoms, increasing to 0.87 (0.80 to 0.94; validated 0.82) with the dipstick findings. A high specificity threshold for the clean-catch model was more accurate and less costly than, and as effective as, clinical judgement. The additional diagnostic utility of dipstick testing was offset by its costs. The cost-effectiveness of the nappy pad model was not clear-cut.

CONCLUSIONS

Clinicians should prioritise the use of clean-catch sampling as symptoms and signs can cost-effectively improve the identification of UTI in young children where clean catch is possible. Dipstick testing can improve targeting of antibiotic treatment, but at a higher cost than waiting for a laboratory result. Future research is needed to distinguish pathogens from contaminants, assess the impact of the clean-catch algorithm on patient outcomes, and the cost-effectiveness of presumptive versus dipstick versus laboratory-guided antibiotic treatment.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

The method of urine sampling is not a valid predictor for vesicoureteral reflux in children after febrile urinary tract infections

INTRODUCTION

The likelihood of detecting vesicoureteral reflux (VUR) after febrile urinary tract infections (UTI) in children logically should correlate with the correct diagnosis of the UTI. Beneath the unspecific symptoms of fever urine analysis is the main diagnostic criterion for the exact diagnosis of febrile UTIs in children. Use of inadequate urine sampling techniques during diagnosis may lead to impaired accuracy in UTI diagnosis. This could lead to the assumption that children, having diagnosed their UTI by the use of possibly inadequate urine sampling techniques should not be evaluated as consequently compared to those, where the diagnosis relied on sterile urine sampling techniques. We hypothesized that children with possibly contaminated urine samples during the initial diagnosis may show a lower rate of VUR in subsequent VCUGs because of a wrong diagnosis initially compared to children, where accurate urine sampling techniques were used.

PATIENTS

Between 2009 and 2014, a total of 555 patients underwent a primary VCUG at our department indicated because of febrile UTIs. Patients with urine collection methods other than bag urine and catheter/suprapubic aspiration (SPA) were excluded from this study (mid-stream urine, potty urine, n = 149). We evaluated 402 patients (male/female 131/271, mean age 1.91 years), VUR rates and grades were compared between patients where urine was sampled by the use of a urine bag only at the time of diagnosis (n = 296, 73.6%) and those where sterile urine sampling (catheter, suprapubic puncture) was performed (n = 106, 26.3%). 4 patients were excluded due to equivocal data on urine sampling.

RESULTS

VUR rate in children after sterile urine sampling using a catheter or SPA accounted to 31.1%. In those where urine samples acquired by the use of urine bags were used, 33.7% showed VUR on subsequent VCUG (p = 0.718). There were no significant differences as to VUR grades or gender, although VUR was much more commonly diagnosed in female patients (37.0% vs 28.2%, p = 0.227) (Figure).

CONCLUSION

Children diagnosed with their UTI by use of bag urine in our experience carried the same risk of showing a VUR in a subsequent VCUG compared to those, where the initial diagnosis relied - beneath clinical criteria - on urine samples acquired by suprapubic puncture or catheterization. Consequently urine-sampling technique during initial UTI diagnosis alone should not be used as predictor for the reliability of UTI diagnosis and should not influence the further management after UTI.

Improving clean-catch contamination rates: A prospective interventional cohort study

OBJECTIVES

The clean-catch method of urine collection carries a high contamination rate. This study aims to evaluate the effects on contamination rate of providing a parent handout and pre-made urine collection pack for clean-catch urine collection.

METHODS

We conducted a single-centre prospective cohort interventional study in a tertiary paediatric ED. All children younger than 24 months who presented from April 2013 to June 2014 requiring a urine sample to be obtained were included. The intervention was provision of a pre-made urine collection pack including a standardised information handout. The primary outcome measure was the difference in proportion of urine contamination in samples obtained via a clean-catch pre- and post-intervention.

RESULTS

The total number of urine specimens included was 288 in the pre-intervention group and 333 in the post-intervention group. Contamination rates were 14.9% in the pre-intervention group and 11.4% in the post-intervention group. There was no statistically significant reduction in contamination (P = 0.19). The contamination rates appeared to be associated with gender, with (pooled) female contamination rates being 16.4% (44/269) and male contamination rates being 10.5% (37/352). Most specimens of urine were collected via the clean-catch method (81.2%), followed by catheter urine specimen (13.7%) and suprapubic aspirate (5.1%). The contamination rate in our study for clean-catch urine collectively was 13%, catheter urine specimen 3.8% and suprapubic aspirate 0%.

CONCLUSION

The contamination rate of clean-catch urine did not improve with the implementation of a pre-made urine collection pack including standardised written instructions.

A Comparison of Bladder Catheterization and Suprapubic Aspiration Methods for Urine Sample Collection From Infants With a Suspected Urinary Tract Infection

This study compares 2 sampling methods for urine cultures in young infants. We analyzed data on urine samples obtained from 83 infants using 2 sources of urine: suprapubic bladder aspiration (SPA) and bladder catheterization. All specimens were subjected to both urinalysis and culture, and the results compared. Eighty-three infants with positive urine culture results obtained by bladder catheterization were subjected to SPA. Of these, only 24 (28.9%) and 20 (24%) yielded positive urine culture and abnormal urinalysis data, respectively. Samples obtained via catheterization had a high false-positive rate (71.1%). The sensitivity and specificity of urinalysis were 66.7% (95% CI, 44.68% to 84.33%) and 93.22% (95% CI, 83.53% to 98.08%), respectively. In infants younger than 12 months, SPA is the best method to avoid bacterial contamination, showing better results than transurethral catheterization.

Urine Contamination in Nontoilet-trained and Uncircumcised Boys

OBJECTIVE

To assess any differences between the initial and midstream urine samples from nontoilet-trained, uncircumcised boys. Contamination during urine collection makes the diagnosis of urinary tract infections (UTIs) difficult in nontoilet-trained children, especially in uncircumcised boys. Whether the contamination comes mainly from the initial stream or the contact between urine and perineal skin is not known in this population.

MATERIALS AND METHODS

A prospective diagnostic study between early and midstream urine samples was conducted on asymptomatic patients with no suspicion of UTI. The clean void method was performed in nontoilet-trained boys under general anesthesia. The exclusion criteria were circumcision, older than 3 years of age, recent antibiotics treatment, and recent UTI. Urinalysis and urine culture were performed, allowing a comparison between early and midstream urine samples.

RESULTS

Forty-four patients were enrolled in the study, and 31 satisfactory samples were obtained. A higher contamination rate was found in the early stream (n = 16; 51%) than in the midstream (n = 5; 16%) (P < .01). The positive culture from the early stream sample was statistically associated with a lower age (P = .02). The contamination rate of the first stream is 3-fold higher than for the midstream when collecting urine for urine culture.

CONCLUSION

The clean void method in nontoilet-trained, uncircumcised boys provides low-quality urine samples for both early and midstream urine samples. The benefit of catching midstream urine samples for the diagnosis of UTI in this population is even more important when the children are young.

Evaluation of the Bladder Stimulation Technique to Collect Midstream Urine in Infants in a Pediatric Emergency Department

OBJECTIVE

Midstream clean-catch urine is an accepted method to diagnose urinary tract infection but is impracticable in infants before potty training. We tested the bladder stimulation technique to obtain a clean-catch urine sample in infants.

MATERIALS AND METHODS

We included 142 infants under walking age who required a urine sample in a cross-sectional study carried out during a 3-months period, from September to November 2014, in the emergency department of the University Children's Hospital of Nice (France). A technique based on bladder stimulation and lumbar stimulation maneuvers, with at least two attempts, was tested by four trained physicians. The success rate and time to obtain urine sample within 3 minutes were evaluated. Discomfort (EVENDOL score ≥4/15) was measured. We estimated the risk factors in the failure of the technique. Chi-square test or Fisher's exact test were used to compare frequencies. T-test and Wilcoxon test were used to compare quantitative data according to the normality of the distribution. Risk factors for failure of the technique were evaluated using a multivariate logistic regression model.

RESULTS

We obtained midstream clean-catch urine in 55.6% of infants with a median time of 52.0 s (10.0; 110.0). The success rate decreased with age from 88.9% (newborn) to 28.6% (>1 y) (p = 0.0001) and with weight, from 85.7% (<4 kg) to 28.6% (>10 kg) (p = 0.0004). The success rate was 60.8% for infants without discomfort (p<0.0001). Heavy weight and discomfort were associated with failure, with adjusted ORs of 1.47 [1.04-2.31] and 6.65 [2.85-15.54], respectively.

CONCLUSION

Bladder stimulation seems to be efficient in obtaining midstream urine with a moderate success rate in our study sample. This could be an alternative technique for infants before potty training but further randomized multicenter studies are needed to validate this procedure.

Validity of bag urine culture for predicting urinary tract infections in febrile infants: a paired comparison of urine collection methods

Purpose

Catheter urine (CATH-U) and suprapubic aspiration (SPA) are reliable urine collection methods for confirming urinary tract infections (UTI) in infants. However, noninvasive and easily accessible collecting bag urine (CBU) is widely used, despite its high contamination rate. This study investigated the validity of CBU cultures for diagnosing UTIs, using CATH-U culture results as the gold standard.

Methods

We retrospectively analyzed 210 infants, 2- to 24-month-old, who presented to a tertiary care hospital's pediatrics department between September 2008 and August 2013. We reviewed the results of CBU and CATH-U cultures from the same infants.

Results

CBU results, relative to CATH-U culture results (≥10⁴ colony-forming units [CFU]/mL) were widely variable, ranging from no growth to ≥10⁵ CFU/mL. A CBU cutoff value of ≥10⁵ CFU/mL resulted in false-positive and false-negative rates of 18% and 24%, respectively. The probability of a UTI increased when the CBU bacterial count was ≥10⁵/mL for all infants, both uncircumcised male infants and female infants (likelihood ratios [LRs], 4.16, 4.11, and 4.11, respectively). UTIs could not be excluded for female infants with a CBU bacterial density of 10⁴-10⁵ (LR, 1.40). The LRs for predicting UTIs based on a positive dipstick test and a positive urinalysis were 4.19 and 3.11, respectively.

Conclusion

The validity of obtaining urine sample from a sterile bag remains questionable. Inconclusive culture results from CBU should be confirmed with a more reliable method.

Midstream clean-catch urine collection in newborns: a randomized controlled study

We aimed to evaluate a recently defined technique based on bladder stimulation and paravertebral lumbar massage maneuvers in collecting a midstream clean-catch urine sample in newborns. A total of 127 term newborns were randomly assigned either to the experimental group or the control group. Twenty-five minutes after feeding, the genital and perineal areas of the babies were cleaned. The babies were held under the armpits with legs dangling. Bladder stimulation and lumbar paravertebral massage maneuvers were only applied to the babies in the experimental group. Success was defined as collection of a urine sample within 5 min of starting the stimulation maneuvers in the experimental group and of holding under the armpits in the control group. The success rate of urine collection was significantly higher in the experimental group (78%) than in the control group (33%; p < 0.001). The median time (interquartile range) for sample collection was 60 s (64.5 s) in the experimental group and 300 s (95 s) in the control group (p < 0.0001). Contamination rates were similar in both groups (p = 0.770).

CONCLUSION

We suggest that bladder stimulation and lumbar paravertebral massage is a safe, quick, and effective way of collecting midstream clean-catch urine in newborns.

Pediatrician noncompliance with the American Academy of Pediatrics guidelines for the workup of UTI in infants

BACKGROUND

The American Academy of Pediatrics (AAP) guidelines on the workup for urinary tract infections (UTIs) in infants discourages the use of bagged urine specimens for urine culture. We report the results of a survey to assess urine collection preferences and adherence to AAP guidelines in clinical practice.

METHODS

A 29-question survey was e-mailed to pediatrician AAP members to determine their preferred method of urine collection in hypothetical infant patients.

RESULTS

Data from 155 respondents were analyzed. In febrile, circumcised boys, up to 18% preferred bagged specimens for urine culture, against AAP recommendations. In febrile girls, 13% of respondents preferred bagged specimens. There was no significant relationship between adherence to AAP guidelines and respondent's age, gender, years in practice, fellowship training, academic affiliation, or other demographic factors.

CONCLUSIONS

Up to 18% of practitioners prefer bagged specimens over more sterile ones in the workup of febrile UTIs in infants, against AAP guidelines.

Prevalence of urinary tract infection in acutely unwell children in general practice: a prospective study with systematic urine sampling

BACKGROUND

Urinary tract infection (UTI) in children may be associated with long-term complications that could be prevented by prompt treatment.

AIM

To determine the prevalence of UTI in acutely ill children ≤ 5 years presenting in general practice and to explore patterns of presenting symptoms and urine sampling strategies.

DESIGN AND SETTING

Prospective observational study with systematic urine sampling, in general practices in Wales, UK.

METHOD

In total, 1003 children were recruited from 13 general practices between March 2008 and July 2010. The prevalence of UTI was determined and multivariable analysis performed to determine the probability of UTI.

RESULT

Out of 597 (60.0%) children who provided urine samples within 2 days, the prevalence of UTI was 5.9% (95% confidence interval [CI] = 4.3% to 8.0%) overall, 7.3% in those < 3 years and 3.2% in 3-5 year olds. Neither a history of fever nor the absence of an alternative source of infection was associated with UTI (P = 0.64; P = 0.69, respectively). The probability of UTI in children aged ≥3 years without increased urinary frequency or dysuria was 2%. The probability of UTI was ≥5% in all other groups. Urine sampling based purely on GP suspicion would have missed 80% of UTIs, while a sampling strategy based on current guidelines would have missed 50%.

CONCLUSION

Approximately 6% of acutely unwell children presenting to UK general practice met the criteria for a laboratory diagnosis of UTI. This higher than previously recognised prior probability of UTI warrants raised awareness of the condition and suggests clinicians should lower their threshold for urine sampling in young children. The absence of fever or presence of an alternative source of infection, as emphasised in current guidelines, may not rule out UTI in young children with adequate certainty.

Contamination rates of different urine collection methods for the diagnosis of urinary tract infections in young children: an observational cohort study

AIMS

  The optimal method for diagnostic collection of urine in children is unclear. National Institute of Health and Clinical Excellence recommend specimens taken by clean catch urine (CCU) for identification of urinary tract infection (UTI). We investigated contamination rates for CCU, suprapubic aspiration (SPA), catheter specimen urine (CSU) and bag specimen urine (BSU) collections.

METHOD

  Retrospective observational cohort study with review of microbiology data and medical records at a large tertiary children's hospital. We reviewed urine culture growth from consecutive first urine specimens of children aged <2 years, over a 3-month period in 2008. Patient demographics, collection method, location (emergency department, inpatient ward), culture growth, history of UTI, urogenital tract abnormality and antibiotic use were assessed. Contamination rates for collection methods were compared using logistic regression.

RESULTS

  Urine culture specimens of 599 children (mean age 7.0 months, 54% male) were included. There were 34% CCU, 16% CSU, 14% SPA, 2% BSU and 34% with unknown sample method. Contamination rates were 26% in CCU, 12% in CSU (odds ratio (OR) 0.4, 95% confidence interval (CI) 0.2-0.8) and 1% in SPA (OR 0.03 95% CI 0.0-0.3). Concurrent antibiotics use was associated with a lower contamination rate. Contamination rates were not associated with age, sex, location, history of UTI or urogenital abnormalities.

CONCLUSION

  Contamination rates in CCU are much higher than in CSU and SPA samples. Ideally, SPA should be used for microbiological assessment of urine in young children. Collection procedures need to be optimised if CCU is used.

Moving from bag to catheter for urine collection in non-toilet-trained children suspected of having urinary tract infection: a paired comparison of urine cultures

OBJECTIVE

To compare, in the same children, urine culture results from bag- versus catheter-obtained specimens with catheter culture as the reference.

STUDY DESIGN

A total of 192 non-toilet-trained children <3 years of age from 2 emergency departments were recruited for this prospective cross-sectional study. All had positive urinalysis results from bag-obtained specimens that were systematically checked with a catheter-obtained specimen before treatment. Results of comparison of urine cultures obtained with these 2 collecting methods are presented.

RESULTS

A total of 7.5% of bag-obtained specimen positive cultures had false-positive results. Twenty-nine percent of bag-obtained specimen cultures with negative results were false negative. Altogether, bag-obtained specimens led to either a misdiagnosis or an impossible diagnosis in 40% of cases versus 5.7% when urethral catheterization was used.

CONCLUSION

Every bag-obtained positive-result urinalysis should be confirmed with a more reliable method before therapy.

Diagnosis of urinary tract infections in children

PURPOSE OF REVIEW

Urinary tract infections remain a significant cause of serious bacterial infections in children and can result in chronic kidney disease. Thus, prompt diagnosis and initiation of treatment of urinary tract infections are paramount objectives.

RECENT FINDINGS

A number of advances in technology have allowed expeditious examination of the urine. Recent meta-analyses evaluated the ability of these tests to determine the presence or absence of urinary tract infection in children. In addition, understanding the prevalence of urinary tract infection in various populations will help guide the clinician to the appropriate level of suspicion and the appropriate work-up for urinary tract infection.

SUMMARY

Although culture of the urine remains the gold standard for diagnosing and treating urinary tract infections, technical considerations including method of collection of the urine as well as the time necessary for culture results remain problematic. More rapid techniques include dipstick analyses for the presence of leukocyte esterase or nitrites, microscopic analysis for white blood cells or bacteria, and automated urine cell analyzer to determine bacterial and white blood cell counts in the urine. Recent results indicate it is possible to limit the number of urine cultures performed by eliminating those that have a low probability of being positive. In addition, recent studies reexamining the prevalence of urinary tract infections in various populations indicate that diagnostic testing can be aimed at those patients who are in the higher-risk groups.