Urine microscopy on a counting chamber for diagnosis of urinary infection

Electrochemical immunosensor detection of urinary lactoferrin in clinical samples for urinary tract infection diagnosis

Urine is the most abundant and easily accessible of all body fluids and provides an ideal route for non-invasive diagnosis of human diseases, particularly of the urinary tract. Electrochemical biosensors are well suited for urinary diagnostics due to their excellent sensitivity, low-cost, and ability to detect a wide variety of target molecules including nucleic acids and protein biomarkers. We report the development of an electrochemical immunosensor for direct detection of the urinary tract infection (UTI) biomarker lactoferrin from infected clinical samples. An electrochemical biosensor array with alkanethiolate self-assembled monolayer (SAM) was used. Electrochemical impedance spectroscopy was used to characterize the mixed SAM, consisted of 11-mercaptoundecanoic acid and 6-mercapto-1-hexanol. A sandwich amperometric immunoassay was developed for detection of lactoferrin from urine, with a detection limit of 145 pg/ml. We validated lactoferrin as a biomarker of pyuria (presence of white blood cells in urine), an important hallmark of UTI, in 111 patient-derived urine samples. Finally, we demonstrated multiplex detection of urinary pathogens and lactoferrin through simultaneous detection of bacterial nucleic acid (16S rRNA) and host immune response protein (lactoferrin) on a single sensor array. Our results represent first integrated sensor platform capable of quantitative pathogen identification and measurement of host immune response, potentially providing clinical diagnosis that is not only more expeditious but also more informative than the current standard.

Absolute and relative accuracy of rapid urine tests for urinary tract infection in children: a meta-analysis

Rapid urine tests, such as microscopy, for bacteria and white cells, and dipsticks, for leucocyte esterase and nitrites, are often used in children that are unwell to guide early diagnosis and treatment of urinary tract infection. We aimed to establish whether these tests were sufficiently sensitive to avoid urine culture in children with negative results and to compare the accuracy of dipsticks with microscopy. Medline, Embase, and reference lists were searched. Studies were included if urine culture results were compared with rapid tests in children. Data were analysed to obtain absolute and relative accuracy estimates. Data from 95 studies in 95 703 children were analysed. Summary estimates for sensitivity and specificity for microscopy for Gram-stained bacteria were 91% (95% CI 80-96) and 96% (92-98), for unstained bacteria were 88% (75-94) and 92% (84-96), for urine white cells were 74% (67-80) and 86% (82-90), for leucocyte esterase or nitrite positive dipstick were 88% (82-91) and 79% (69-87), and for nitrite-only positive dipstick were 49% (41-57) and 98% (96-99). Microscopy for bacteria with Gram stain had higher accuracy than other laboratory tests with relative diagnostic odds ratio compared with bacteria without Gram stain of 8.7 (95% CI 1.8-41.1), white cells of 14.5 (4.7-44.4), and nitrite of 22.0 (0.7-746.3). Microscopy for white cells should not be used for the diagnosis of urinary tract infection because its accuracy is no better than that of dipstick, laboratory facilities are needed, and results are delayed. Rapid tests are negative in around 10% of children with a urinary tract infection and cannot replace urine culture. If resources allow, microscopy with Gram stain should be the single rapid test used.

How does study quality affect the results of a diagnostic meta-analysis?

BACKGROUND

The use of systematic literature review to inform evidence based practice in diagnostics is rapidly expanding. Although the primary diagnostic literature is extensive, studies are often of low methodological quality or poorly reported. There has been no rigorously evaluated, evidence based tool to assess the methodological quality of diagnostic studies. The primary objective of this study was to determine the extent to which variations in the quality of primary studies impact the results of a diagnostic meta-analysis and whether this differs with diagnostic test type. A secondary objective was to contribute to the evaluation of QUADAS, an evidence-based tool for the assessment of quality in diagnostic accuracy studies.

METHODS

This study was conducted as part of large systematic review of tests used in the diagnosis and further investigation of urinary tract infection (UTI) in children. All studies included in this review were assessed using QUADAS, an evidence-based tool for the assessment of quality in systematic reviews of diagnostic accuracy studies. The impact of individual components of QUADAS on a summary measure of diagnostic accuracy was investigated using regression analysis. The review divided the diagnosis and further investigation of UTI into the following three clinical stages: diagnosis of UTI, localisation of infection, and further investigation of the UTI. Each stage used different types of diagnostic test, which were considered to involve different quality concerns.

RESULTS

Many of the studies included in our review were poorly reported. The proportion of QUADAS items fulfilled was similar for studies in different sections of the review. However, as might be expected, the individual items fulfilled differed between the three clinical stages. Regression analysis found that different items showed a strong association with test performance for the different tests evaluated. These differences were observed both within and between the three clinical stages assessed by the review. The results of regression analyses were also affected by whether or not a weighting (by sample size) was applied. Our analysis was severely limited by the completeness of reporting and the differences between the index tests evaluated and the reference standards used to confirm diagnoses in the primary studies. Few tests were evaluated by sufficient studies to allow meaningful use of meta-analytic pooling and investigation of heterogeneity. This meant that further analysis to investigate heterogeneity could only be undertaken using a subset of studies, and that the findings are open to various interpretations.

CONCLUSION

Further work is needed to investigate the influence of methodological quality on the results of diagnostic meta-analyses. Large data sets of well-reported primary studies are needed to address this question. Without significant improvements in the completeness of reporting of primary studies, progress in this area will be limited.

Rapid tests and urine sampling techniques for the diagnosis of urinary tract infection (UTI) in children under five years: a systematic review

BACKGROUND

Urinary tract infection (UTI) is one of the most common sources of infection in children under five. Prompt diagnosis and treatment is important to reduce the risk of renal scarring. Rapid, cost-effective, methods of UTI diagnosis are required as an alternative to culture.

METHODS

We conducted a systematic review to determine the diagnostic accuracy of rapid tests for detecting UTI in children under five years of age.

RESULTS

The evidence supports the use of dipstick positive for both leukocyte esterase and nitrite (pooled LR+ = 28.2, 95% CI: 17.3, 46.0) or microscopy positive for both pyuria and bacteriuria (pooled LR+ = 37.0, 95% CI: 11.0, 125.9) to rule in UTI. Similarly dipstick negative for both LE and nitrite (Pooled LR- = 0.20, 95% CI: 0.16, 0.26) or microscopy negative for both pyuria and bacteriuria (Pooled LR- = 0.11, 95% CI: 0.05, 0.23) can be used to rule out UTI. A test for glucose showed promise in potty-trained children. However, all studies were over 30 years old. Further evaluation of this test may be useful.

CONCLUSION

Dipstick negative for both LE and nitrite or microscopic analysis negative for both pyuria and bacteriuria of a clean voided urine, bag, or nappy/pad specimen may reasonably be used to rule out UTI. These patients can then reasonably be excluded from further investigation, without the need for confirmatory culture. Similarly, combinations of positive tests could be used to rule in UTI, and trigger further investigation.

Urinary tract infections: what's new?

PURPOSE

This review provides practicing urologists with important basic information about urinary tract infections (UTIs) that can be applied to everyday clinical problems.

MATERIALS AND METHODS

A review is presented of provocative and controversial concepts in the current literature.

RESULTS

Bacterial virulence mechanisms are critical for overcoming the normal host defenses. Increasing antimicrobial resistance of uropathogens has led to reconsideration of traditional treatment recommendations in many areas. For effective patient management the first issue is to define complicating urological factors. Managing complicated urinary tract infections, particularly in urology, is determined by clinical experience to define the pertinent anatomy and to determine the optimal interventions. New clinical data are summarized on UTIs in long-term care patients, behavioral risks for UTI in healthy women and anatomical differences associated with an increased risk for UTI. The rationale is presented for UTI prophylaxis using cranberry juice, immunization and bacterial interference. Current treatment trends for UTI include empiric therapy (without urine culture and sensitivity testing), short-course therapy, patient-administered (self-start) therapy and outpatient therapy for uncomplicated pyelonephritis.

CONCLUSIONS

Recommendations for treating patients with UTIs have changed based on basic science and clinical experience.

Automated urinalysis. Evaluation of the Sysmex UF-50

We assessed the Sysmex UF-50 for reproducibility of results and carryover rate by performing between- and within-run precision analyses on 315 urine samples, evaluated the feasibility of using the UF-50 to measure urinary cellular and noncellular components by comparing results from the UF-50 with results of manual urinalysis using the Kova system, and performed side-by-side comparison of the within-run reproducibility from the UF-50, the UF-100, and the Kova system. Results from the UF-50 and UF-100 were highly reproducible, and the carryover rate was 0.5% or less for the urinary components. In between-run precision assays, the coefficients of variation for UF-50 results for all cellular components were less than 10%. The agreement (gamma statistics) between values from the UF-50 and the Kova system was excellent for RBC, WBC, and bacterial counts. The cell counts from the UF-50 for RBCs, WBCs, epithelial cells, and bacteria were 52%, 63%, 54%, and 110%, respectively, of those measured by manual urinalysis. The UF-50 performed quantitative analysis in 72 seconds, compared with 330 seconds for manual methods. The UF-50 is suitable for the first screening to detect hematuria, pyuria, and bacteriuria.

Urinalysis and urinary tract infection: update for clinicians

Dysuria is a common presenting complaint of women and urinalysis is a valuable tool in the initial evaluation of this presentation. Clinicians need to be aware that pyuria is the best determinate of bacteriuria requiring therapy and that values significant for infection differ depending on the method of analysis. A hemocytometer yields a value of > or = 10 WBC/mm3 significant for bacteriuria, while manual microscopy studies show > or = 8 WBC/high-power field reliably predicts a positive urine culture. In cases of uncomplicated symptomatic urinary tract infection, a positive value for nitrites and leukocyte esterase by urine dipstick can be treated without the need for a urine culture. Automated urinalysis used widely in large volume laboratories provides more sensitive detection of leukocytes and bacteria in the urine. With automated microscopy, a value of > 2 WBC/hpf is significant pyuria indicative of inflammation of the urinary tract. In complicated cases such as pregnancy, recurrent infection or renal involvement, further evaluation is necessary including manual microscopy and urine culture with sensitivities.

Urinary tract infection in the pediatric patient

Little attention has been focused on the identification of urinary tract infection (UTI) in young febrile children in the emergency department, despite recent information that suggests both a high prevalence and significant associated morbidity in this population. Most UTIs that lead to scarring or diminished kidney growth occur in children younger than age 4 years, especially babies in the first year of life. Overall, prevalence rates of UTI in febrile infants in the emergency department are approximately 3% to 5%, with higher rates for white girls, uncircumcised boys, and those without another potential source for fever. Prevalence and risk factors are given so that clinicians may identify those febrile children at particularly high or low risk of UTI for selective management. Culturing methods, urine screening tests, and culture interpretation are reviewed and management strategies based on these results are suggested.

Screening tests for urinary tract infection in children: A meta-analysis

OBJECTIVE

To review systematically and to summarize the existing literature regarding performance of rapid diagnostic tests for urinary tract infection (UTI) in children.

DESIGN

Systematic review and meta-analysis.

METHODS

Published articles reporting the performance of urine dipstick tests (leukocyte esterase [LE] and/or nitrite), Gram stain, or microscopic analysis of spun or unspun urine in the diagnosis of UTI in children </=12 years of age. Articles were identified through a comprehensive MEDLINE search, and those articles meeting a priori inclusion criteria were selected. Eligibility criteria included the use of urine culture as the reference standard, independent comparison of urine culture with the results of one of the screening tests, definition of positive screening test results provided, only pediatric patients included or evaluable separately, and both gold standard and screening test performed on all patients. For each test, heterogeneity of reported sensitivity and specificity of all studies was determined. The subgroups of studies with similar definitions of UTI and age of study subjects were analyzed separately to account for some of the differences in reported results. When significant unexplained heterogeneity among studies precluded simple combining of results, a summary receiver-operator characteristic curve was fitted for each screening test, from which pooled estimates of true-positive rate (TPR; ie, sensitivity) and false-positive rate (FPR; 1-specificity) were calculated.

PRIMARY RESULTS

A total of 1489 titles were identified by the MEDLINE search; 26 articles met all criteria for inclusion. There was significant heterogeneity among studies for nearly all tests for both TPR and FPR, which was explained only partially by the stringency of the definition of UTI or age of subjects studied. Based on the pooled estimates, the presence of any bacteria on Gram stain on an uncentrifuged urine specimen had the best combination of sensitivity (0.93) and FPR (0.05). Urine dipstick tests performed nearly as well, with a sensitivity of 0.88 for the the presence of either LE or nitrite and an FPR of 0.04 for the presence of both LE and nitrite. Pyuria had lower TPR and higher FPR: for presence of >5 white blood cells/high-power field in a centrifuged urine sample, the TPR was 0.67 and the FPR was 0.21, whereas for >10 white blood cells per mm(3) in uncentrifuged urine, the TPR was 0.77 and the FPR was 0.11.

CONCLUSIONS

Both Gram stain and dipstick analysis for nitrite and LE perform similarly in detecting UTI in children and are superior to microscopic analysis for pyuria.

Congenitally small kidneys with reflux as a common cause of nephropathy in boys

Congenital maldevelopment is sometimes found in small kidneys with ureteral reflux. However, the incidence of congenitally small kidneys and the frequency of its association with ureteral reflux remains unknown. Ultrasound scanning, performed in 4,000 apparently healthy neonates or young infants (males 2,129, females 1,871), detected 51 children suspected of having small kidneys. A careful ultrasound re-examination performed one month later in 45 of the 51 children confirmed small kidneys in eight children, one bilateral and seven unilateral. Dimercaptosuccinate (DMSA) renoscintigraphy revealed small kidneys with generally diminished uptake in six infants and no uptake unilaterally in the other two infants. One of the 12 children, who had normal findings on the initial scanning and subsequently developed urinary infection, was later diagnosed having unilateral small kidney with generally reduced DMSA uptake. All seven infants having small kidneys with reduced tracer uptake were male (incidence, 1:300 boys). All eight small kidneys in the seven boys and four of the six contralateral non-small kidneys were associated with ureteral reflux, while neither of the two infants with a non-functioning kidney had ureteral reflux. Serial ultrasounds documented the poor growth of all small kidneys. Thus, congenitally small kidneys with generally diminished DMSA uptake were highly associated with ureteral reflux and especially observed in boys.