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

Predictive System Implementation to Improve the Accuracy of Urine Self-Diagnosis with Smartphones: Application of a Confusion Matrix-Based Learning Model through RGB Semiquantitative Analysis

Urinalysis, an elementary chemical reaction-based method for analyzing color conversion factors, facilitates examination of pathological conditions in the human body. Recently, considerable urinalysis-centered research has been conducted on the analysis of urine dipstick colors using smartphone cameras; however, such methods have a drawback: the problem of reproducibility of accuracy through quantitative analysis. In this study, to solve this problem, the function values for each concentration of a range of analysis factors were implemented in an algorithm through urine dipstick RGB semi-quantitative color analysis to enable real-time results. Herein, pH, glucose, ketones, hemoglobin, bilirubin, protein (albumin), and nitrites were selected as analysis factors, and the accuracy levels of the existing equipment and the test application were compared and evaluated using artificial urine. In the semi-quantitative analysis, the red (R), green (G), and blue (B) characteristic values were analyzed by extracting the RGB characteristic values of the analysis factors for each concentration of artificial urine and obtaining linear function values. In addition, to improve the reproducibility of detection accuracy, the measurement value of the existing test equipment was set to an absolute value; using a machine-learning technique, the confusion matrix, we attempted to stabilize test results that vary with environment.

Association of Pyuria with Uropathogens in Young Children

OBJECTIVE

To examine the association between uropathogens and pyuria in children <24 months of age.

STUDY DESIGN

A retrospective study of children <24 months of age evaluated in the emergency department for suspected urinary tract infection (UTI) with paired urinalysis and urine culture during a 6-year period. Bagged urine specimens or urine culture growing mixed/multiple urogenital organisms were excluded. Analysis was limited to children with positive urine culture as defined by the American Academy of Pediatrics clinical practice guideline culture thresholds.

RESULTS

Of 30 462 children, 1916 had microscopic urinalysis and positive urine culture. Urine was obtained by transurethral in-and-out catheterization in 98.3% of cases. Pyuria (≥5 white blood cells per high-powered field) and positive leukocyte esterase (small or more) on the urine dipstick were present in 1690 (88.2%) and 1692 (88.3%) of the children respectively. Children with non-Escherichia coli species were less likely to exhibit microscopic pyuria than children with E coli (OR 0.24, 95% CI 0.17-0.34) with more pronounced effect on Enterococcus and Klebsiella (OR 0.08, 95% CI 0.03-0.18 and OR 0.18, 95% CI 0.11-0.27 respectively). Similarly, positive leukocyte esterase was less frequently seen in non-E coli uropathogens compared with E coli.

CONCLUSIONS

Pyuria and leukocyte esterase are not sensitive markers to identify non-E coli UTI in young children. More sensitive screening biomarkers are needed to identify UTI with these uropathogens.

Preoperative bacteriuria positivity on urinalysis increases wound complications in primary total hip arthroplasty regardless of the urine culture result

BACKGROUND

Current evidence does not recommend screening urine culture and curing asymptomatic bacteriuria (ASB) before joint arthroplasty. The bacteriuria count on pre-operative urinalysis is a more common clinical parameter. We aimed to investigate whether the bacteriuria count on preoperative urinalysis can increase postoperative wound complications in primary total hip arthroplasty (THA).

METHODS

We conducted a retrospective study that included patients who underwent primary THA in our institution from 2012 to 2018. We obtained preoperative urinalysis results before THA during the same hospitalization and identified patients with abnormal urinalysis. Receiver operating characteristic (ROC) curves were first generated to evaluate the predicted value of leukocyte esterase (LE), nitrite, bacteriuria, and pyuria in the urinalysis for superficial wound infection. Then, all included patients were divided into two groups according to the preoperative urinalysis: a bacteriuria-positive group and a bacteriuria-negative group. The primary outcome was the superficial wound infection rate within 3 months postoperatively, and the secondary outcomes included wound leakage, prosthetic joint infection (PJI), pulmonary infection, urinary tract infection (UTI), readmission rate within 3 months postoperatively, and length of stay (LOS) during hospitalization. We utilized univariable analyses to compare the outcomes between the two groups. A multivariable logistic regression model was generated to explore the potential association between bacteriuria and the risk of superficial wound infection, wound leakage, and readmission rate controlling for baseline values.

RESULTS

A total of 963 patients were included in the study. One hundred sixty patients had abnormal urinalysis. The AUCs for LE, nitrite, bacteriuria, and pyuria were 0.507 (95% confidence interval (CI), 0.315 to 0.698), 0.551 (0.347 to 0.756), 0.675 (0.467 to 0.882), and 0.529 (0.331 to 0.728), respectively. Bacteriuria was diagnostically superior to LE, nitrite, and pyuria. Among the 963 patients, 95 had a positive bacteriuria on preoperative urinalysis, and only 9 (9.5%) had a positive urine culture. Compared with the bacteriuria-negative group, the bacteriuria-positive group had a higher superficial wound infection rate (4.2% vs. 0.6%, P = 0.008), higher wound leakage rate (11.6% vs. 4.5%, P = 0.007), higher readmission rate (5.3% vs. 1.3%, P = 0.015) within 3 months postoperatively and longer LOS (6.19 ± 2.89 days vs. 5.58 ± 2.14 days, P = 0.011). After adjustment, the bacteriuria-positive group had a significantly increased risk of superficial wound infection (OR = 7.587, 95%CI: 2.002 to 28.755, P = 0.003), wound leakage (OR = 3.044, 95%CI: 1.461 to 6.342, P = 0.003), and readmission (OR = 4.410, 95%CI: 1.485 to 13.097, P = 0.008).

CONCLUSION

Preoperative bacteriuria positivity on urinalysis significantly increased the risk of postoperative wound complications, readmission, and LOS in primary THA regardless of the result of the urine culture. Urinalysis is a fast and cost-acceptable test whose advantages have been underestimated.

LEVEL OF EVIDENCE

Level III, observational study.

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.

Design of a novel midstream fluid waste sample collection device for patients

Reducing the contamination rates in mid-stream urine samples is a challenge. A novel design for a mid-stream urine sample collection device, which uses a novel mechanism to separate the mid-stream flow from the fore-stream and end-stream flows based on flow speed, is presented. The device, supplied in two parts, is designed to be clipped to a toilet and used in a seated position, which improves ease of use for disabled patients. As there is no mixing of the flow types during use, it is hypothesised that contamination rates should be lower than many competing designs. The all-polymer design is easy to use by both men and women, due to the addition of a form-fitting funnel and is designed to collect samples directly into containers of the same standard currently issued, allowing easy and hygienic collection. Due to its complex shape, the main body of the device is produced by a non-conventional injection moulding process. The holder can be produced using standard injection moulding technology. The two parts are designed to be assembled together by the user by means of a simple interference fit, which removes the cost of assembly altogether.

Correlation of Chemical Urinalysis to Microscopic Urinalysis and Urine Culture: Implications for Reflex Urinalysis Workflows

BACKGROUND

Urinalysis (UA) reflex testing approaches, which offer potential for savings in labor and result turnaround time, may rely on the performance of a chemical UA screen to determine which urine samples need microscopic UA and/or urine culture. We correlated chemical UA, microscopic UA, and urine culture results to determine the performance of chemical UA as a screening tool for reflex testing approaches.

METHODS

Consecutive UA results for 9127 tests (simultaneous chemical UA and microscopic UA) were retrospectively reviewed and correlated. Urine culture results were also correlated for 3127 samples that had urine culture ordered within 24 h of UA. Positivity criteria for each UA method were predefined.

RESULTS

Chemical UA yielded the following performance specifications for predicting microscopic findings: 93.0% sensitivity, 56.9% specificity, 64.7% positive predictive value, 90.5% negative predictive value. 3.2% of samples were negative by chemical UA but positive by microscopic UA. Of the samples with urine culture results available, 6.3% were negative by chemical UA but had clinically-significant positive urine cultures.

CONCLUSIONS

Reflex testing of microscopic UA and/or urine culture dependent from chemical UA results provides a feasible opportunity to reduce unnecessary testing.

Evaluation of Acridine Orange Staining for a Semi-Automated Urinalysis Microscopic Examination at the Point-of-Care

A urinary tract infection (UTI) can be diagnosed via urinalysis, consisting of a dipstick test and manual microscopic examination. Point-of-care (POC) image-based systems have been designed to automate the microscopic examination for low-volume laboratories or low-resource clinics. In this pilot study, acridine orange (AO) was evaluated as a fluorescence-based contrast agent to aid in detecting and enumerating urine sediment specific for diagnosing a UTI. Acridine orange staining of epithelial cells, leukocytes, and bacteria provided sufficient contrast to successfully implement image segmentation techniques, which enabled the extraction of classifiable morphologic features. Surface area bounded by each cell border was used to differentiate the sediment; epithelial cells were larger than 500μm², bacteria were less than 30μm², and leukocytes in between. This image-based semi-automated technique using AO resulted in similar cell counts to the clinical results, which demonstrates the feasibility of AO as an aid for POC urinalysis systems.