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

Outpatient urine collection methods for paediatric urinary tract infections: Systematic review of diagnostic accuracy studies

AIM

To investigate the diagnostic test accuracy of urine collection methods for urinary tract infections in outpatient children.

METHODS

A systematic literature review until April 2021 (Medline, Web of Science, Embase, Cinahl) to examine the diagnostic test accuracy of urine culture on collection methods for urinary tract infection in outpatient children below 18 years. Contamination rates were studied as secondary outcome. The risk of bias was assessed using the QUADAS-2 criteria. Two-by-two tables were extracted in duplicate to calculate sensitivities, specificities, and likelihood ratios with 95% confidence intervals.

RESULTS

The search identified seven relevant studies. Clean catch compared to catheterization in children less than 90 days showed a sensitivity and specificity of 97% and 89% (95% CI: 84%-100% and 67%-99%), respectively. Adhesive bags compared to catheterization showed a sensitivity of 83% (95% CI: 75%-90%) and specificity of 91% (95% CI: 83%-96%). There was a similar diagnostic accuracy when comparing urine sampling by means of adhesive bags versus nappy pads. The contamination rate was 5% for clean catch, 30%-80% for adhesive bags and 64% for nappy pads.

CONCLUSION

Nappy pads and adhesive bags are easy to use with comparable accuracy but are extremely prone to contamination. Clean-catch urine sampling might be an accurate alternative in young infants in ambulatory care.

Clinical Evaluation of a Novel Urine Collection Kit Using Filter Paper in Neonates: An Observational Study

Urine bags are commonly used to collect urine samples from neonates. However, the sample can be contaminated by stool, or detachment of the bag due to body movement can lead to failure of the collection. A qualitative urine collection kit containing ten filter papers of 3.2 mm diameter was developed and clinically verified among 138 neonates. During a single diaper change (approximately 3 h), the rate of urine collection was calculated. Urine collection was considered to be successful if any filter paper in the urine collection sheet turned from blue to white. Of the 127 neonates who passed urine, 122 had a change in the filter paper. The urine collection rate was 96%, with changes in all 10 filter papers observed in 98 neonates (80%). Urine collection rate was not influenced by sex (p = 1.00), age at collection (p = 0.72), preterm birth (p = 1.00), low birth weight (p = 0.92), or fecal contamination (p = 1.00). The incidence of dermatitis was not higher than in the group in which urine bags were used (urine collection kit: 2/68 [3%]; urine bag: 5/68 [7%]; p = 0.44). Novel urine collection kits using filter paper can collect samples from neonates safely and with a high probability of success.

Clinical utility of procalcitonin in febrile infants younger than 3 months of age visiting a pediatric emergency room: a retrospective single-center study

BACKGROUND

Fever in infants under 90 days of age is highly likely to be caused by a severe bacterial infection (SBI) and it accounts for a large number of patients visiting the pediatric emergency room. In order to predict the bacterial infection and reduce unnecessary treatment, the classic classification system is based on white blood cell (WBC) count, urinalysis, and x-ray, and it is modified and applied at each center by incorporating recently studied biomarkers such as c-reactive protein (CRP) or procalcitonin (PCT). This study analyzed the usefulness of PCT in predicting SBI when applied along with the existing classification system, including CRP, among infants less than 90 days old who visited with a fever at a single institution pediatric emergency center.

METHODS

We retrospectively reviewed the medical records of patients younger than 3 months of age who presented with fever at the Seoul Asan Medical Center pediatric emergency room between July 2017 and October 2018.

RESULTS

A total of 317 patients were analyzed, and 61 were diagnosed with SBI, among which urinary tract infection (UTI) accounted for the largest proportion (55/61, 90.2%). There were differences in WBC, neutrophil proportion, CRP, and PCT between the SBI group and the non-SBI group, and the AUC values of WBC, CRP, and PCT were 0.651, 0.804, and 0.746, respectively. When using the cut-off values of CRP and PCTs as 2.0 mg/dL and 0.3 ng/mL, respectively, the sensitivity and specificity for SBI were 49.2/89.5, and 54.1/87.5, respectively. WBC, CRP, and PCT were statistically significant for predicting SBI in multivariate analysis (odds ratios 1.066, 1.377, and 1.291, respectively). When the subjects were classified using the existing classification criteria, WBC and CRP, the positive predictive value (PPV) and negative predictive value (NPV) were 29.3 and 88.7%, respectively, and when PCT was added, the PPV and NPV were 30.7 and 92%, respectively, both increased.

CONCLUSION

PCT is useful for predicting SBI in children aged 3 months or less who visit the emergency room with a fever. It is useful as a single biomarker, and when used in conjunction with classic biomarkers, its diagnostic accuracy is further increased.

Urine collection methods and dipstick testing in non-toilet-trained children

Urinary tract infection is a commonly occurring paediatric infection associated with significant morbidity. Diagnosis is challenging as symptoms are non-specific and definitive diagnosis requires an uncontaminated urine sample to be obtained. Common techniques for sampling in non-toilet-trained children include clean catch, bag, pad, in-out catheterisation and suprapubic aspiration. The pros and cons of each method are examined in detail in this review. They differ significantly in frequency of use, contamination rates and acceptability to parents and clinicians. National guidance of which to use differs significantly internationally. No method is clearly superior. For non-invasive testing, clean catch sampling has a lower likelihood of contamination and can be made more efficient through stimulation of voiding in younger children. In invasive testing, suprapubic aspiration gives a lower likelihood of contamination, a high success rate and a low complication rate, but is considered painful and is not preferred by parents. Urine dipstick testing is validated for ruling in or out UTI provided that leucocyte esterase (LE) and nitrite testing are used in combination.

Midstream Clean-Catch Urine Culture Obtained by Stimulation Technique versus Catheter Specimen Urine Culture for Urinary Tract Infections in Newborns: A Paired Comparison of Urine Collection Methods

OBJECTIVE

The group of Herreros Fernández developed a new, safe, quick, and successful technique for collecting midstream clean-catch urine(MS-CCU) in newborns based on bladder stimulation and lumbar paravertebral massage maneuvers. The purpose of this study was to compare the contamination rates of catheter specimen urine (CSU) and MS-CCU by a lumbar/sacral stimulation technique in newborns.

MATERIALS AND METHODS

Full-term newborns ranging in age from 2 to 28 days who needed an investigation for a presumed urinary tract infection (UTI) were included in the study. Two samples, MS-CCU by lumbar/sacral stimulation technique and CSU, were collected consecutively for each patient. Suitable samples were obtained from 90 patients.

RESULTS

The contamination rate in MS-CCU cultures (n = 24/90, 26.66%) was higher than in CSU cultures (n = 9/90, 10%), and the difference was statistically significant (p = 0.039). Thirteen patients had UTI according to both samples (14.14%). In urine analysis, while there was no statistically significant difference in bacteriuria (p = 0.61) and nitrite positivity (p = 0.14) between patients with and without UTI, pyuria (p = 0.01) and leukocyte esterase positivity (p = 0.01) were higher in patients with UTI, and the difference was statistically significant.

CONCLUSION

The contamination rate in MS-CCU cultures was two and a half times greater than in the CSU culture samples. Thus, MS-CCU cannot replace the catheter for the diagnosis of UTI.

Urine collection methods used for non-toilet-trained children in pediatric emergency departments in France: A medical practice analysis

INTRODUCTION

Since April 2015, the French Society of Pediatrics has encouraged suprapubic aspiration (SA) and urethral catheterization (UC) for urine collection in non-toilet-trained children suspected of having urinary tract infections (UTIs) and has tried to reduce the use of urine bag (UB).

OBJECTIVE

To analyze the medical practices concerning urine collection methods used for non-toilet-trained children in pediatric emergency departments in France.

METHODS

We conducted a descriptive medical practice study in October 2017. All members of the French Society of Pediatric Nephrology received two questionnaires about urine collection methods used for non-toilet-trained children, distinguishing between male and female patients, and about the corresponding analgesic protocols used in their pediatric emergency departments.

RESULTS

In total, 26 centers completed questionnaires concerning female patients. UC was performed in cases of fever associated with urinary tract malformations in 14 of 26 centers (54%). UB was used in cases of fever of unknown origin lasting for more than 48h in 17 of 26 centers (65%), in cases of fever associated with UTI symptoms in 14 of 26 centers (54%), and in cases of fever in infants under 3 months of age in 16 of 26 centers (61%). The questionnaires concerning male patients were completed by 30 centers. UB was the initially used urine collection method in all situations with, respectively, 22 of 30 (73%), 27 of 30 (90%), 23 of 30 (77%), and 22 of 30 (73%) centers. The analgesic protocol for urine collection is not well established in France.

CONCLUSION

UC for urine collection in pediatric emergency departments in France is underused despite the national recommendations and the greater diagnostic power of this method compared with UB.

Pitfalls of diagnosing urinary tract infection in infants and young children

BACKGROUND

The aim of this study was to examine the sensitivity and specificity of pyuria-based diagnosis of urinary tract infection (UTI) in urine collected by transurethral catheterization, and the reliability of diagnosis of pyuria in urine collected in a perineal bag. The gold standard for UTI diagnosis is significant colony counts of a single organism in urine obtained in a sterile manner.

METHODS

We enrolled 301 patients who underwent medical examination at the present hospital for possible UTI between January 2005 and December 2009. We collected 438 urine samples by transurethral catheterization. We investigated the accuracy of pyuria-based diagnosis of UTI using transurethral catheterization urine specimens, and the reliability of diagnosis of pyuria using bag-collected urine specimens.

RESULTS

The false-negative rate of UTI diagnosis based on pyuria in transurethral catheterization urine sediments was 9.0%; there was no significant difference in the false-negative rate of UTI diagnosis between boys and girls. Approximately 28% of pyuria-positive bag-collected urine specimens were pyuria negative on transurethral catheterization; this rate was significantly higher in girls than in boys (56.7% vs. 8.9%, P < 0.0001).

CONCLUSIONS

The absence of pyuria in transurethral catheterization urine sediments does not rule out UTI. Pyuria in bag-collected urine specimens frequently consists of urine leukocytes from external genitalia as well as from the urinary tract.

Performance of urinalysis tests and their ability in predicting results of urine cultures: a comparison between automated test strip analyser and flow cytometry in various subpopulations and types of samples

Aims

Results of urinalysis are available earlier than urine culture results. If urinalysis can predict results of culture, early decision can be made on treatment and whether urine samples should be cultured. This study sought to compare the performance of urinalysis tests by automated test strip analyser (nitrite and leucocyte esterase) with flow cytometry (bacteria and white cell count) in different subpopulations and types of samples.

Methods

Consecutive urine samples (n=2351) from a population with a median age of 45 years, 37.2% men, were tested. Sensitivity, specificity, positive predictive value and negative predictive value (NPV) of the tests were calculated using contingency tables. The gold standard was positive urine culture with cut-off >105 CFU/mL.

Results

14% of the cultures were positive (95.6% monomicrobial, 74.7% Enterobacteriaceae). Overall, nitrite test was the most specific (98.7%) but the least sensitive (43.2%). Bacteria count was the most sensitive (91.7%) and highly specific (87.5%). In infants <24 months, the sensitivity of bacteria count was reduced (86.1%), but specificity was high (95.9%). The specificity of nitrite was reduced in urine from the in-and-out procedure (81.9%). The sensitivity of bacteria count was reduced in bag specimens urine (83.3%) and in urine from indwelling catheter (84.7%). All tests showed a high NPV. The NPV of the combined flow cytometry tests was higher than those of automated test strip analyser (99.1% vs 97.4%).

Conclusions

Overall, the performance of urinalysis is excellent. Flow cytometry tests performed better than automated test strip analyser in ruling out urine to be cultured.