Automated urinalysis and urine dipstick in the emergency evaluation of young febrile children

Assessing Concordance of Results: A Comparative Study of the Manual and Automated Urinalysis Methods

Introduction

An accurate urine analysis is a good indicator of the status of the renal and genitourinary system. However, limited studies have been done on comparing the diagnostic performance of the fully automated analyser and manual urinalysis especially in Ghana. This study evaluated the concordance of results of the fully automated urine analyser (Sysmex UN series) and the manual method urinalysis at the Komfo Anokye Teaching Hospital in Kumasi, Ghana. Methodology. Sixty-seven (67) freshly voided urine samples were analysed by the automated urine analyser Sysmex UN series and by manual examination at Komfo Anokye Teaching Hospital, Ghana. Kappa and Bland-Altman plot analyses were used to evaluate the degree of concordance and correlation of both methods, respectively.

Results

Substantial (κ = 0.711, p < 0.01), slight (κ = 0.193, p = 0.004), and slight (κ = 0.109, p < 0.001) agreements were found for urine colour, appearance, and pH, respectively, between the manual and automated methods. A strong and significant correlation (r = 0.593, p < 0.001) was found between both methods for specific gravity with a strong positive linear correlation observed for red blood cell count (r = 0.951, R2 = 0.904, p < 0.001), white blood cell count (r = 0.907, R2 = 0.822, p < 0.001), and epithelial cell count (r = 0.729, R2 = 0.532, p < 0.001). A perfect agreement of urine chemistry results in both methods was observed for nitrite 67 (100%) (κ = 1.000, p < 0.001) with a fair agreement for protein 46 (68.7%) (κ = 0.395, p < 0.001). A strong agreement was found in both methods for the presence of cast 65 (97.0%) (κ = 0.734, p < 0.001) with no concordance observed for the presence of crystals (κ = 0.115, p = 0.326) and yeast-like cells (YLC) (κ = 0.171, p = 0.116).

Conclusion

The automated and manual methods showed similar performances and good correlation, especially for physical and chemical examination. However, manual microscopy remains necessary to classify urine sediments, particularly for bacteria and yeast-like cells. Future research with larger samples could help validate automated urinalysis for wider clinical use and identify areas requiring improved automated detection capabilities.

Accuracy of NGAL as a Biomarker for Urinary Tract Infection in Young Febrile Children: An Individual Patient Data Meta-Analysis

OBJECTIVE

To compare the accuracy of urine neutrophil gelatinase-associated lipocalin (NGAL) and leukocyte esterase (LE) for the diagnosis of urinary tract infection (UTI) in children.

STUDY DESIGN

We performed a systematic review and individual patient data meta-analysis of studies that examined urine NGAL as a marker of UTI in children <18 years of age. We created a standardized definition of UTI and applied it to all included children. We compared sensitivity, specificity, and the area under the receiver operating characteristic curve (AUC) of NGAL with LE.

RESULTS

We included individual patient data from 3 studies for a total of 845 children. Included children had a mean age of 0.9 years (SD, 0.6 years). Using a cutoff of 32.7 ng/mL, NGAL had a sensitivity of 90.3% (95% CI: 83.2%-95.0%) and specificity of 93.7% (95% CI: 91.7%-95.4%) for the diagnosis of UTI. LE, using a cutoff of ≧ trace had a sensitivity of 81.1% (95% CI: 72.5%-87.9%) and specificity of 97.0% (95% CI: 95.4%-98.1%). The AUC for NGAL was 0.95 (95% CI: 0.92-0.98). The AUC for LE was 0.90 (95% CI: 0.86-0.93).

CONCLUSION

In young, febrile children, urinary NGAL is more sensitive for the diagnosis of UTI than LE but is slightly less specific.

Diagnostic value of biomarkers for paediatric urinary tract infections in primary care: systematic review and meta-analysis

Background

Accurate diagnosis of urinary tract infection is essential as children left untreated may suffer permanent renal injury.

Aim

To compare the diagnostic values of biomarkers or clinical prediction rules for urinary tract infections in children presenting to ambulatory care.

Design and setting

Systematic review and meta-analysis of ambulatory care studies.

Methods

Medline, Embase, WOS, CINAHL, Cochrane library, HTA and DARE were searched until 21 May 2021. We included diagnostic studies on urine or blood biomarkers for cystitis or pyelonephritis in children below 18 years of age. We calculated sensitivity, specificity and likelihood ratios. Data were pooled using a bivariate random effects model and a Hierarchical Summary Receiver Operating Characteristic analysis.

Results

Seventy-five moderate to high quality studies were included in this review and 54 articles in the meta-analyses. The area under the receiver-operating-characteristics curve to diagnose cystitis was 0.75 (95%CI 0.62 to 0.83, n = 9) for C-reactive protein, 0.71 (95% CI 0.62 to 0.80, n = 4) for procalcitonin, 0.93 (95% CI 0.91 to 0.96, n = 22) for the dipstick test (nitrite or leukocyte esterase ≥trace), 0.94 (95% CI 0.58 to 0.98, n = 9) for urine white blood cells and 0.98 (95% CI 0.92 to 0.99, n = 12) for Gram-stained bacteria. For pyelonephritis, C-reactive protein < 20 mg/l had LR- of 0.10 (95%CI 0.04–0.30) to 0.22 (95%CI 0.09–0.54) in children with signs suggestive of urinary tract infection.

Conclusions

Clinical prediction rules including the dipstick test biomarkers can support family physicians while awaiting urine culture results. CRP and PCT have low accuracy for cystitis, but might be useful for pyelonephritis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12875-021-01530-9.

Clinical Features for the Diagnosis of Pediatric Urinary Tract Infections: Systematic Review and Meta-Analysis

PURPOSE

Accurate diagnosis of urinary tract infection in children is essential because children left untreated can experience permanent renal injury. We aimed to assess the diagnostic value of clinical features of pediatric urinary tract infection.

METHODS

We performed a systematic review and meta-analysis of diagnostic test accuracy studies in ambulatory care. We searched the PubMed, Embase, Web of Science, Cumulative Index to Nursing and Allied Health Literature, Cochrane Central Register of Controlled Trials, Health Technology Assessment, and Database of Abstracts of Reviews of Effects databases from inception to January 27, 2020 for studies reporting 2 × 2 diagnostic accuracy data for clinical features compared with urine culture in children aged <18 years. For each clinical feature, we calculated likelihood ratios and posttest probabilities of urinary tract infection. To estimate summary parameters, we conducted a bivariate random effects meta-analysis and hierarchical summary receiver operating characteristic analysis.

RESULTS

A total of 35 studies (N = 78,427 patients) of moderate to high quality were included, providing information on 58 clinical features and 6 prediction rules. Only circumcision (negative likelihood ratio [LR-] 0.24; 95% CI, 0.08-0.72; n = 8), stridor (LR- 0.20; 95% CI, 0.05-0.81; n = 1), and diaper rash (LR- 0.13; 95% CI, 0.02-0.92; n = 1) were useful for ruling out urinary tract infection. Body temperature or fever duration showed limited diagnostic value (area under the receiver operating characteristic curve 0.61; 95% CI, 0.47-0.73; n = 16). The Diagnosis of Urinary Tract Infection in Young Children score, Gorelick Scale score, and UTIcalc (https://uticalc.pitt.edu) might be useful to identify children eligible for urine sampling.

CONCLUSIONS

Few clinical signs and symptoms are useful for diagnosing or ruling out urinary tract infection in children. Clinical prediction rules might be more accurate; however, they should be validated externally. Physicians should not restrict urine sampling to children with unexplained fever or other features suggestive of urinary tract infection.

Fast and Sensitive: Automated Point-of-Care Urine Dips

OBJECTIVE

Point-of-care (POC) urine dipstick is a highly used test in the pediatric emergency department (PED) owing to its fast turn-around time and inexpensive cost. Past studies have shown hand-held urine dipsticks and automated urinalysis in children younger than 48 months to be sensitive predictors for urinary tract infection (UTI). It is hypothesized that POC dip testing is as accurate as laboratory urinalysis in the diagnosis of UTI.

METHODS

A retrospective chart review was conducted on patients (aged birth through 18 years) presenting to a PED between January 2015 and December 2015. Eligible subjects included those that had a POC dip, laboratory urinalysis (lab UA), and urine culture performed during their PED visit. Subjects were selected, using a random number generator; 334 charts were selected. A positive POC dip was defined as having a positive leukocyte esterase or the presence of nitrites. A positive lab UA was defined as having a positive leukocyte esterase, nitrites, or greater than 10 white blood cells per high-power field. Urine culture was used as the criterion standard for comparison.

RESULTS

A total of 334 subjects' charts were reviewed. Sensitivity and specificity of the POC dip were 91.4% (95% confidence interval [CI], 76.9%-98.2%) and 63.9% (95% CI, 57.2%-69.3%); lab UA, 91.4% (95% CI, 76.9%-98.2%) and 63.9% (95% CI, 58.2%-69.3%); and lab dip, 88.6% (95% CI, 73.3%-96.8%) and 65.6% (95% CI, 59.9%-70.9%).

CONCLUSIONS

Point-of-care dips are as sensitive in detecting UTI as the lab UA. A prospective study could allow for further demographic evaluation of POC dip diagnosed UTI.

Updated Italian recommendations for the diagnosis, treatment and follow-up of the first febrile urinary tract infection in young children

AIM

Our aim was to update the recommendations for the diagnosis, treatment and follow-up of the first febrile urinary tract infection in young children, which were endorsed in 2012 by the Italian Society of Pediatric Nephrology.

METHODS

The Italian recommendations were revised on the basis of a review of the literature published from 2012 to October 2018. We also carried out an ad hoc evaluation of the risk factors to identify children with high-grade vesicoureteral reflux or renal scarring, which were published in the previous recommendations. When evidence was not available, the working group held extensive discussions, during various meetings and through email exchanges.

RESULTS

Four major modifications have been introduced. The method for collecting urine for culture and its interpretation has been re-evaluated. We have reformulated the algorithm that guides clinical decisions to proceed with voiding cystourethrography. The suggested antibiotics have been revised, and we have recommended further restrictions of the use of antibiotic prophylaxis.

CONCLUSION

These updated recommendations have now been endorsed by the Italian Society of Pediatric Nephrology and the Italian Society for Pediatric Infectivology. They can also be used to compare other recommendations that are available, as a worldwide consensus in this area is still lacking.

Evaluation of BacterioScan 216Dx in Comparison to Urinalysis as a Screening Tool for Diagnosis of Urinary Tract Infections in Children

Urinalysis (UA) has routinely been used as a screening tool prior to urine culture set up. BacterioScan 216Dx is an FDA-cleared semiautomated system to detect bacterial growth in urine. The aim of this study was to evaluate 216Dx in comparison to UA for diagnosis of urinary tract infection (UTI) in children. Clean-catch, unpreserved urine samples from children aged <18 years were tested by 216Dx, and positive urine samples in media were processed for direct bacterial identification by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. Sensitivity and specificity of 216Dx and urinalysis (UA) were determined against urine culture. Of 287 urine samples obtained from children (median age, 108 months), 44.0% and 56.0% were UA positive and negative, respectively, while 216Dx detected 27% and 73% as positive and negative, respectively. Compared to culture, the overall sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 216Dx versus UA were 92.1% versus 97.3%, 82.7% versus 63.8%, 44.8% versus 29.1%, and 98.6% versus 99.3%, respectively. Among 216Dx true-positive (TP) samples (n = 35), 77.0% were successfully identified directly from broth by MALDI-TOF. Among urine samples that were identified as contaminated by culture (n = 127; 44%), the 216Dx detected 93 (73.0%) as negative while UA detected 69 (54.0%) as negative. Although the sensitivities of 216Dx and UA are comparable, the specificity of 216Dx was higher than that of UA. The 216Dx can be used as an alternative/adjunct screening tool to UA to rule out urinary tract infection (UTI) in children. Compared to culture, the faster turnaround time (3 hours) of 216Dx has the potential to reduce unnecessary antibiotic use and improve patient management.

Urine flow cytometry is an adequate screening tool for urinary tract infections in children

Diagnosing a urinary tract infection in children is often difficult due to non-specific symptoms and requires invasive and time-consuming procedures. Flow cytometry is a new and rapid method of analyzing urine to confirm or exclude UTIs. We have investigated the sensitivity and specificity of urine flow cytometry (Sysmex UF1000i) compared to conventional diagnostic techniques in a prospective study from January 1, 2014 until January 1, 2015. All children under 13 years of age with a suspicion of urinary tract infection were screened using both urine flow cytometry and urine culture. A urinary tract infection was defined as the combination of leukocyturia (≥ 25 leukocytes per μl) and a positive urine culture in the presence of clinical symptoms. A total number of 412 urine samples were collected, of which 63 cases (15.3%) were positive for a urinary tract infection. Receiver operating characteristic analysis showed an area under the curve of 0.97 (95% confidence interval h0.93-1.00) for the bacterial count. When using a cut-off value of 250 bacteria/μl in the presence of leukocyturia, the sensitivity for urinary tract infection is 0.97 with a negative predictive value of 97%, and the specificity is 0.91 with a positive predictive value of 90%.Conclusion: Flow cytometry-based bacterial and leukocyte count analysis is a time-efficient method of diagnosing or ruling out urinary tract infection in children, with a higher sensitivity and specificity than dipstick and microscopic analysis. What is known • Screening for urinary tract infections in children is difficult due to invasive and time-consuming procedures. • There is both over- and under-treatment of urinary tract infections due to the delays in accurate diagnosing. What is new • Flow cytometry is a rapid and accurate method to provide useful information in the diagnosis of urinary tract infection in children. When negative, flow cytometry can exclude urinary tract infection in children with a high degree of confidence. When flow cytometry is positive, the possibility of a urinary tract infection in children is increased.

Using urine nitrite sticks to test for urinary tract infection in children aged < 2 years: a meta-analysis

BACKGROUND

This study aimed to determine whether nitrite sticks are as sensitive at detecting urinary tract infection (UTI) in children <2 years as they are in older children.

METHODS

I reanalysed data on using nitrite sticks to detect UTIs for children aged either < 2 or 2-18 years. For sensitivity, evidence of a UTI was defined as level 1 when a single uropathogen grew ≥ 10⁵ colony forming units/ml (cfu/ml) in two urine samples, level 2 when just one sample was cultured or a threshold of < 10⁵ cfu/ml was used, and level 3 if mixed growths or Staphylococcus albus was considered to be positive. For specificity, children were defined as uninfected if they had 1 sterile urine culture. I also reanalysed our previously published data by age.

RESULTS

The sensitivity was lower for children aged < 2 years (11 studies, 1321 subjects) than for older children (9 studies, 295 subjects), whether the level-1 values or all the studies were analysed (Fisher's exact test, p < 0.0001 for both). The level-1 sensitivities were 0.23 in the infants and 0.81 among older children (odds ratio = 0.07, 95% confidence interval 0.03-0.18). The specificity was very high in infants (10 studies, 1783 cases) and older children (7 studies, 5952 cases), at 0.990 and 0.996.

CONCLUSIONS

Nitrite sticks only have a 23% sensitivity in children aged < 2 years, so cannot reliably rule out UTIs. A positive nitrite stick test is about 99% likely to indicate a UTI in children of any age.

Urine Flow Cytometry in the Diagnosis of Urinary Tract Infection

OBJECTIVES

To determine the cut-off value of bacteria with urine flow cytometer in diagnosing urinary tract infection.

METHODS

From a total of 546 patients admitted to the hospital with urinary tract infection (UTI), two urine samples were obtained for each patient. Urine samples in sterile containers were divided into two; first for urine culture and second for simultaneous measurement with UF-1000i flow cytometry device. The presence of a single type of bacteria over 10³ CFU/mL in urine culture was accepted as UTI.

RESULTS

Of 546 patients, 210 (38.5%) were boys and 336 (61.5%) were girls. There was no growth in 489 (89.5%) of the urine specimens and 57 (10.4%) samples showed growth (>10³ CFU/ml). A threshold of 10 bacteria/μL in flow cytometry (sensitivity = 100%) showed the best compatibility with culture. Diagnostic values in terms of sensitivity (100%), specificity (43.5%), negative predictive value (100%) and positive predictive value (17.7%) were satisfactory.

CONCLUSIONS

The UF-1000i flow cytometer can give results quickly and exclude UTI using the determined number of cut-off bacteria at low cost. Thus, if Sysmex UF-1000i is used, quick and accurate results can be obtained and unnecessary laboratory tests can be prevented. Also, patient convenience can be increased.

Microscopic Bacteriuria Detected by Automated Urinalysis for the Diagnosis of Urinary Tract Infection

OBJECTIVE

To evaluate the test performance of microscopic bacteriuria by automated urinalysis for presumptive urinary tract infection (UTI) in young children.

STUDY DESIGN

This is a retrospective cross-sectional study of children aged <2 years evaluated for UTI in a single large emergency department with paired automated microscopic urinalysis and culture. Test characteristics were calculated for automated microscopic bacteriuria and pyuria, and a practical diagnostic threshold of bacteriuria was determined. Standard test performance measures and receiver operator characteristic curves were generated. The diagnostic performance of bacteriuria was compared with microscopic pyuria.

RESULTS

Two thousand five hundred fifty-four children with a median age of 6.1 months were studied, 19% of whom had a positive urine culture. Automated microscopic bacteriuria ≥1+ resulted in a positive likelihood ratio (LR+) of 4.5 (95% CI, 3.9-5.2) and negative LR (LR-) of 0.52 (95% CI, 0.47-0.57). Pyuria alone (≥5 WBC/high-power field) had a LR+ of 4.5 (95% CI, 4.1-5.0) and a LR- of 0.14 (95% CI, 0.11-0.18), whereas the addition of automated microscopic bacteriuria ≥1+ improved the LR+ to 16.3 (95% CI, 12.6-21.1) but raised the LR- to 0.51 (95% CI, 0.47-0.56). Test performance of automated microscopic bacteriuria measured by area under the curve analysis was lower (0.73; 95% CI, 0.70-0.76) than for pyuria (0.92; 95% CI, 0.90-0.93). Isolated automated microscopic bacteriuria without pyuria occurred in only 204 patients (8.0%), among whom only 20 (9.8%) had a positive urine culture.

CONCLUSIONS

Microscopic bacteriuria measured by automated urinalysis augments the diagnostic value of pyuria for identifying presumptive UTI in young children aged <2 years. Bacteriuria is diagnostically inferior to microscopic pyuria, and in children with bacteriuria without pyuria, presumptive UTI is unlikely.

Urine Concentration and Pyuria for Identifying UTI in Infants

BACKGROUND

Varying urine white blood cell (WBC) thresholds have been recommended for the presumptive diagnosis of urinary tract infection (UTI) among young infants. These thresholds have not been studied with newer automated urinalysis systems that analyze uncentrifuged urine that might be influenced by urine concentration. Our objective was to determine the optimal urine WBC threshold for UTI in young infants by using an automated urinalysis system, stratified by urine concentration.

METHODS

Retrospective cross-sectional study of infants aged <3 months evaluated for UTI in the emergency department with paired urinalysis and urine culture. UTI was defined as ≥50 000 colony-forming units/mL from catheterized specimens. Test characteristics were calculated across a range of WBC and leukocyte esterase (LE) cut-points, dichotomized into specific gravity groups (dilute <1.015; concentrated ≥1.015).

RESULTS

Twenty-seven thousand infants with a median age of 1.7 months were studied. UTI prevalence was 7.8%. Optimal WBC cut-points were 3 WBC/high-power field (HPF) in dilute urine (likelihood ratio positive [LR+] 9.9, likelihood ratio negative [LR‒] 0.15) and 6 WBC/HPF (LR+ 10.1, LR‒ 0.17) in concentrated urine. For dipstick analysis, positive LE has excellent test characteristics regardless of urine concentration (LR+ 22.1, LR‒ 0.12 in dilute urine; LR+ 31.6, LR‒ 0.22 in concentrated urine).

CONCLUSIONS

Urine concentration should be incorporated into the interpretation of automated microscopic urinalysis in young infants. Pyuria thresholds of 3 WBC/HPF in dilute urine and 6 WBC/HPF in concentrated urine are recommended for the presumptive diagnosis of UTI. Without correction of specific gravity, positive LE by automated dipstick is a reliably strong indicator of UTI.

Diagnosis of Urinary Tract Infections in Children

Urinary tract infections (UTIs) are a common occurrence in children. The management and laboratory diagnosis of these infections pose unique challenges that are not encountered in adults. Important factors, such as specimen collection, urinalysis interpretation, culture thresholds, and antimicrobial susceptibility testing, require special consideration in children and will be discussed in detail in the following review.