Reevaluating the true diagnostic accuracy of dipstick tests to diagnose urinary tract infection using Bayesian latent class analysis

OBJECTIVE

Previous studies on diagnostic accuracy of dipstick testing for leukocyte esterase (LE) and nitrite to diagnose urinary tract infection (UTI) had used urine culture, which is an imperfect gold standard. Estimates of diagnostic accuracy obtained using the classical gold standard framework might not reflect the true diagnostic accuracy of dipstick tests.

METHODS

We used the dataset from a prospective, observational study conducted in the emergency department of a teaching hospital in southern India. Patients with a clinical suspicion of UTI underwent dipstick testing for LE and nitrite, urine microscopy, and urine culture. Based on the results of urine microscopy and culture, UTI was classified into definite, probable, and possible. Patients with microscopic pyuria and a positive urine culture were adjudicated as definite UTI. Unequivocal imaging evidence of emphysematous pyelonephritis or perinephric collections was also considered definite UTI. We estimated the diagnostic accuracy of LE and nitrite tests using the classical analysis (assuming definite UTI as gold standard) and two different Bayesian latent class models (LCMs; 3-tests in 1-population and 2-tests in 2-populations models).

RESULTS

We studied 149 patients. Overall, 64 (43%) patients had definite, 76 (51%) had probable, and 2 (1.3%) had possible UTI; 7 (4.6%) had alternate diagnoses. In classical analysis, LE was more sensitive than nitrite (87.5% versus 70.5%), while nitrite was more specific (24% versus 58%). The 3-tests in 1-population Bayesian LCM indicated a substantially better sensitivity and specificity for LE (98.1% and 47.6%) and nitrite (88.2% and 97.7%). True sensitivity and specificity of urine culture as estimated by the model was 48.7% and 73.0%. Estimates of the 2-tests in 2-populations model were in agreement with the 3-tests in 1-population model.

CONCLUSIONS

Bayesian LCMs indicate a clinically important improvement in the true diagnostic accuracy of urine dipstick testing for LE and nitrite. Given this, a negative dipstick LE would rule-out UTI, while a positive dipstick nitrite would rule-in UTI in our study setting. True diagnostic accuracy of urine dipstick testing for UTI in various practice settings needs reevaluation using Bayesian LCMs.

Utility of point-of-care Gram stain by physicians for urinary tract infection in children ≤36 months

Urinary tract infection (UTI) in children requires early diagnosis and treatment to prevent repeated UTI and renal scarring. This study aimed to evaluate the usefulness of the point-of-care Gram stain by physicians for suspected UTI in children at Okinawa Chubu Hospital as a rapid diagnostic test.A single-center, retrospective study was undertaken between January 2011 and December 2015. Patients aged 36 months or younger who were reviewed had suspected UTI in the emergency room or outpatient clinic. Urine culture, urinalysis, and point-of-care Gram stain were performed on a single specimen. Patients with structural or functional urological defects requiring routine catheterization were excluded. We compared the diagnostic performance among the rapid diagnostic tests (i.e., pyuria, point-of-care Gram stain, or both). Kappa statistics were used to evaluate the agreement between the results of point-of-care Gram stain and morphotypes of urine culture with the 95% CI (bias corrected bootstrap interval). We also analyzed which antibiotics were more susceptible to the bacteria of urine culture results, selected by the results of point-of-care Gram stain or empirical treatment based on the Japanese guidelines by McNemar test.Of 1594 patients reviewed in the study, 1546 were eligible according to our inclusion criteria. Using urine culture as the gold standard for UTI, the sensitivity and specificity of pyuria were 73.2% and 95.1%, whereas those of the point-of-care Gram stain were 81.4% and 98.2%, respectively. The concordance rate between the morphotypes of bacteria detected by point-of-care Gram stain and those of urine culture was 0.784 (kappa coefficient) (95% CI 0.736-0.831). Furthermore, the proportion of "susceptible" in the minimum inhibitory concentration of pathogen-targeted treatment based on the point-of-care Gram stain was higher than that of empirical therapy (exact McNemar significance probability: .0001).Our analysis suggests that the point-of-care Gram stain is a useful rapid diagnostic tool for suspected UTI in young children. Pathogen-targeted treatment based on the point-of-care Gram stain would lead to better antibiotic selection compared with empirical therapy.

Lower urinary tract symptoms that predict microscopic pyuria

Introduction and hypothesis

Urinary dipsticks and culture analyses of a mid-stream urine specimen (MSU) at 10⁵ cfu ml⁻¹ of a known urinary pathogen are considered the gold standard investigations for diagnosing urinary tract infection (UTI). However, the reliability of these tests has been much criticised and they may mislead. It is now widely accepted that pyuria (≥1 WBC μl⁻¹) detected by microscopy of a fresh unspun, unstained specimen of urine is the best biological indicator of UTI available. We aimed to scrutinise the greater potential of symptoms analysis in detecting pyuria and UTI.

Methods

Lower urinary tract symptom (LUTS) descriptions were collected from patients with chronic lower urinary tract symptoms referred to a tertiary referral unit. The symptoms informed a 39-question inventory, grouped into storage, voiding, stress incontinence and pain symptoms. All questions sought a binary yes or no response. A bespoke software package was developed to collect the data. The study was powered to a sample of at least 1,990 patients, with sufficient power to analyse 39 symptoms in a linear model with an effect size of Cohen’s f² = 0.02, type 1 error probability = 0.05; and power (1-β); 95% where β is the probability of type 2 error). The inventory was administered to 2,050 female patients between August 2004 and November 2011. The data were collated and the following properties assessed: internal consistency, test–retest reliability, inter-observer reliability, internal responsiveness, external responsiveness, construct validity analysis and a comparison with the International Consultation on Incontinence Modular Questionnaire for female lower urinary tract symptoms (ICIQ-FLUTS). The dependent variable used as a surrogate marker of UTI was microscopic pyuria. An MSU sample was sent for routine culture.

Results

The symptoms proved reliable predictors of microscopic pyuria. In particular, voiding symptoms correlated well with microscopic pyuria (χ² = 88, df = 1, p < 0.001). The symptom inventory has significant psychometric characteristics as below: test–retest reliability: Cronbach’s alpha was 0.981; inter-observer reliability, Cronbach’s alpha was 0.995, internal responsiveness F = 221, p < 0.001, external responsiveness F = 359, df = 5, p < 0.001. The correlation coefficients for the domains of the ICIQ-FLUTS were around R = 0.5, p < 0.001.

Conclusion

This symptoms score performed well on the standard, psychometric validation. The score changed in response to treatment and in a direction appropriate to the changes in microscopic pyuria. It correlated with measures of quality of life. It would seem to make a good candidate for monitoring treatment progress in ordinary clinical practice.

Screening for urine abnormalities among preschool children in western Saudi Arabia

OBJECTIVES

To estimate the frequency of urinary problems among preschool children.

METHODS

In this cross-sectional study, 1000 preschool asymptomatic children attending the outpatient clinics of the Children's Hospital, Taif, Kingdom of Saudi Arabia between August 2013 and December 2013 were subjected to dipstick urine analysis. Microscopic examination was performed for the abnormal dipstick samples, and children with hematuria were investigated for kidney function.

RESULTS

Dipstick urine analysis revealed abnormal findings in 25.1% of the screened children. The most common dipstick abnormalities were positive nitrite test in 18.1%, hematuria in 16.9%, and positive leukocyte esterase test in 14.3% of the cases. The most common abnormality in microscopic urine examination was crystals in 13% of the cases. Pyuria were evident in 5% of cases and hematuria in 2.5%. The most common bacteria in positive urine culture samples was Escherichia coli in 62.6%.

CONCLUSION

In view of these important findings, dipstick screening should be implemented in preschool children. 

Changes in urine levels of substance P, vasoactive intestinal peptide and calcitonin-gene-related peptide in patients with urinary tract infections

Urinary tract infections (UTI) are important health problems and predisposing causes of UTI are not entirely known. Neuro-immune interactions play an important role in human health and disease. Capsaicin-sensitive sensory nerves which in nerve bladder extensively regulate immune system through neuropeptides such as substance P (SP), calcitonin-gene related peptide (CGRP) and vasoactive intestinal peptide (VIP). In addition these neuropeptides also have anti-bacterial effects. To determine how the levels of these peptides changes during UTI, 67 patients (50-90 years-old) diagnosed with UTI in Akdeniz University Faculty of Medicine Hospital were compared with 37 healthy people 50 years or older as the control group. Additionally, 7 patients with UTI symptoms (dysuria, urgency) but with sterile pyuria were also included in the study. Urine samples from 15 patients, whose symptoms regressed with control urine cultures being sterile, were taken after completion of the treatments. Urine neuropeptide levels were determined by ELISA. CGRP levels are significantly higher in patients with UTI, but did not associate with pyuria whereas SP and VIP levels were significantly lower in patients with sterile pyuria, indicating sensory nerve deficiency. Since CGRP exerts immunosuppressive effects, increased levels of the peptide may predispose to UTI. Furthermore, the connection between the observed sensory nerve deficiency and sterile pyuria warrants further studies.

Validity of quantitative unspun urine microscopy, dipstick test leucocyte esterase and nitrite tests in rapidly diagnosing urinary tract infections

OBJECTIVES

Rapid diagnostic tests can screen out negative samples and can save valuable time and money. The study was conducted to assess the usefulness of leukocyte esterase, nitrate reductase and quantitative microscopic unspun urine wet mount examination in rapidly diagnosing urinary tract infections (UTI).

METHODS

Four hundred and fifty samples were tested by semi-quantitative culture on cysteine lactose electrolyte deficient medium, microscopic examination of unspun urine for significant pyuria, dipstick leucocyte esterase test (LET) and nitrite test (NT). Culture was used as gold standard to evaluate the performance of direct microscopy and dipstick tests.

RESULTS

Urine culture examination revealed significant bacteriuria (>10(5) cfu/ml) 98 (21.8%), in urine samples. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and the diagnostic odds ratio (DOR) of the dip-stick LET were 73.5%, 58.5%, 33.0%, 88.8%, and 3.9 respectively; those of the dip-stick NT were 57.1%, 78.7%, 42.7%, 86.8%, and 4.9 respectively; and those for microscopic significant pyuria detection were 68.4%, 60.8%, 32.7%, 87.3%, and 3.4 respectively. Highest sensitivity (95.9%), NPV (97.9%) and DOR (25.7) was obtained on combining microscopy and dip-stick LET and NT (either of them positive). This can potentially cut costs by 79%.

CONCLUSION

Quantitative unspun urine wet mount microscopy and dipstick tests for leucocyte esterase and nitrite test should be added into routine laboratory practices for faster diagnosis of UTI.

Risks of repeated visits for uninvestigated dyspepsia in three community hospitals of Khon Kaen, Thailand

BACKGROUND

Uninvestigated dyspepsia (UD) is common and only 26.4% of these are peptic ulcer disease, while 50% are non-ulcer dyspepsia. A recent study found that nephrolithiasis with urinary tract infection may have the dyspeptic symptoms.

OBJECTIVE

The authors searched for any associations between repeated UD and pyuria, hematuria and other factors.

MATERIAL AND METHOD

A case-control study was performed. It consisted of 489 patients with repeated UD who had visited community hospitals for at least two times per year and 489 controls sampled from the data of the subjects, free of dyspeptic symptoms, from the multi-stage random survey for subjective health complaints in the same province. Multivariate logistic regression models were used for case-control comparisons.

RESULTS

By logistic regression analysis, UD was significantly associated with problems caused by purine-rich foods (PRFs), chronic fatigue, flank paresthesia, hematuria, myofascial pain, and pyuria. The respective adjusted odds ratios and 95% confidence interval (CI) were: 6.67 (4.58, 9.68), 5.06 (3.46, 7.40), 3.98 (2.41, 6.60), 2.97 (2.01, 4.38), 1.91 (1.32, 2.76) and 1.58 (1.01, 2.45). The variables of age (> 48), sex, dysuria, poly-arthralgia, headache and back pain were not significantly associated with UD. The foods that aggravated UD were bamboo shoots, fermented rice noodles, beef alcohol and insects. The rate of pyuria and hematuria was significantly increased with the number of visits within a year [p-value (Chi-square for trend), 0.015 and 0.032].

CONCLUSION

These findings indicate that pyuria, hematuria, and purine-rich foods were associated with repeated hospital visits for dyspepsia.

[Influence of blood cells in urine samples on results of screening for urothelial carcinoma with NMP22 bladder chek]

We compared the sensitivity of Bladder Chek NMP22 with that of urine cytology in bladder cancer patients. Further, we evaluated the usefulness of Bladder Chek NMP22 in patients with benign diseases such as cystitis, urolithiasis, and benign prostate hyperplasia (BPH) and examined how blood cells in urine samples affect the results of Bladder Chek NMP22. Patients with macroscopic hematuria were excluded from this study. Of 77 bladder cancer patients, Bladder Chek NMP22 showed positive in 46.8%, while urine cytology in 33.8% (p = 0.16). Bladder Chek NMP22 and urine cytology showed positive in 31.8 and 0.0% in G1 (p = 0.004), 51.2 and 46.3% in G2 (p = 0.66) and 57.1 and 50% in G3 (p = 0.71); 44.4 and 88.9% in Tis (p = 0.052), 25.6 and 15.4% in Ta (p = 0.27), 72.2 and 33.3% in T1 (p = 0.02) and 81.8 and 54.5% in T2 or higher (p = 0.18), respectively. In bladder cancer patients with microscopic hematuria or pyuria, the positive rates of Bladder Chek NMP22 were 82.1 and 73.1%, respectively, whereas they were 26.5% (p < 0.001) and 33.3% (p = 0.002), respectively, in those without hematuria or pyuria. In 36 cystitis, 20 urolithiasis, and 19 BPH patients, the positive rates of Bladder Chek NMP22 were 58.3, 25.0 and 5.5%, respectively. Bladder Chek NMP22 showed higher sensitivity for detection of bladder cancer, especially in low-grade and low-stage cancers than urine cytology, but the result was likely affected by blood cells in urine samples. Thus, although Bladder Chek NMP22 may be less useful as the first device for screening of urothelial cancer in patients with hematuria or pyuria, it may show results of high quality when used in patients with negative urine cytology after excluding benign diseases.

Clinical study of complicated urinary tract infection using 'The UTI Criteria (Draft Fourth Edition)': measurement methods for pyuria

OBJECTIVE

To evaluate the influences the change of the measurement method of pyuria from conventional centrifuged sediment to microchamber uncentrifuged urine for the results of evaluation of antimicrobial agents in clinical study against complicated urinary tract infections. From the viewpoint of international harmonization of judgement criteria, the recent method for counting white blood cells (WBC) in urine has changed from using uncentrifuged urine to using a microchamber in all countries.

METHODS

Targeted diseases were non-catheterized complicated urinary tract infection, and cefcapene pivoxil hydrochloride or levofloxacin were used as antimicrobial drug. Pyuria was examined using the counting chamber method, a quantitative method using uncentrifuged urine with a microchamber, and the sedimentation method.

RESULTS

Overall clinical efficacy in early evaluation by the two methods in measuring pyuria was evaluated as different in eight patients (7.3%). It was rated excellent in 63 (52.9%), moderate in 32 patients (26.9%) and poor in 24 (20.2%) with an efficacy rate of 79.8% using the counting chamber method, and excellent in 68 (57.1%), moderate in 27 (22.7%) and poor in 24 (20.2%) with an efficacy rate of 79.8% using the conventional sedimentation method

CONCLUSION

No significant difference was seen between the two methods of WBC count in urine.

Can the urine dipstick test reduce the need for microscopy for assessment of systemic lupus erythematosus disease activity?

OBJECTIVE

Urine microscopic examination is an important component of the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). We investigated whether the urine dipstick test can reduce the need for microscopy for the assessment of SLEDAI.

METHODS

We studied 269 urine samples from 259 SLE patients with Albustix and Hemastix reagent strips. The results were compared to concomitant microscopic examination of urinary sediment.

RESULTS

When trace red blood cell was defined as the cutoff, the sensitivity, specificity, and negative predictive value (NPV) of the Hemastix urine test were 0.98, 0.53, and 0.99, respectively, for hematuria; 0.82, 0.47, and 0.90, respectively, for the presence of pyuria; and 0.91, 0.44, and 0.98, respectively, for the presence of casts by microscopic examination. When proteinuria of 1+ was defined as the cutoff, the sensitivity, specificity, and NPV of the Albustix test were 1.00, 0.46, and 0.99, respectively, for urinary casts; and 0.82, 0.49, and 0.90, respectively, for the presence of pyuria. When both Albustix and Hemastix were applied as screening test, urine microscopy could be reduced by 27%; however, 8% of cases with normal Albustix and Hemastix tests had at least one abnormality on urine microscopy examination.

CONCLUSION

In patients with SLE, a combination of Albustix and Hemastix urine tests showed reasonable sensitivity to detect abnormalities in urine sediment. Based on these results, routine urine microscopy can be limited to SLE patients with abnormal Albustix or Hemastix tests. Rarer causes of abnormal renal function in lupus, such as tubulointerstitial nephritis or drug induced interstitial nephritis, would be manifested by pyuria and therefore would not necessarily be detected by changes in the blood and protein detectors on the urine dipstick.

Criteria for urinary tract infection in the elderly: variables that challenge nursing assessment

Urinary tract infections (UTIs) are common in the elderly, yet there is much disagreement in the literature regarding many aspects of this condition. To assist the nurse in developing optimum care strategies, UTI criteria in the elderly are discussed. Using the most recent knowledge to guide clinical assessment and intervention skills, the longterm care facility nurse and nurses who care for the elderly can influence positive outcomes in this challenging population.

Urinary Tract Infections: Does the Smell Really Tell?

Asymptomatic bacteriuria is considered a transient and benign condition in the geriatric population. Before a diagnosis of a urinary tract infection (UTI) can be made, symptoms and significant bacteriuria must be present. One of these symptoms is malodorous urine. Other symptoms of a UTI, typical in the younger population, have been found to be absent or misleading in the older adult population. Though early detection of UTIs improves outcomes, unnecessary laboratory tests are costly and time-consuming, and may encourage inappropriate antibiotic therapy. The purpose of this study was to determine if urine odor is an accurate predictor of a UTI in the older adult incontinent nursing home population. Ninety-seven recently wet incontinence pads of residents in six Midwestern nursing homes were evaluated for odor within 1 hour of voiding. These results were compared to microscopy and culture results of clean-catch urine samples from these individuals. Defining a UTI as either bacteriuria or bacteriuria and pyuria, using urine odor to identify a UTI resulted in error in one third of cases. Results of this study indicate smell of urine in incontinence pads may be an absent or misleading symptom for UTIs in elderly nursing home residents.

A study for the improvement of the cytological urine examination performances in upper tract infection diagnosis

Diagnosis of the location of upper and lower urinary tract infection (UTI) is necessary in defining the therapeutic conduct that has a different period and intensity according to the infection location and in prognosis. Many studies show the lack of clinical criteria peculiarity in revealing the different location of UTI. As a result, the correct location of the level in which UTI develops is the necessity of paraclinical investigations. Urinary sample examination, in which urinary sediment microscopy is essential, is a reliable technique in fast detection and localization of UTI. Finding, in pyuria context, the classic significant bacteriuria (> or = 10(5) CFU/ml) or lower value bacteriuria (< or = 10(4) CFU/ml) confirms the UTI diagnosis. The upper tract infection prognosis increases when leukocyte cylinders, characteristic for pyelonephritis, appear together with intact or degraded leukocytes, single or grouped. We settled an algorithm to examine the urine samples in order to: Concentrate and preserve the structural integrity of leukocytes and cylinders, examining the conventional urinary sediment Precisely identify and differentiate these elements by vital coloration (leukocyte peroxidase coloration and Sternheimer - Malbin coloration) to establish more accurate the UTI level. The vital coloration for leukocyte peroxidase has cytological specificity, confirming the pyuria and the cylinders that contain leukocytes (leukocytary, granular, mixed) and obviously ameliorates the reliability and reproducibility of the urinary sediment cytological exam.

Predicting urine culture results by dipstick testing and phase contrast microscopy

AIMS

Urine is the most frequently received clinical specimen for bacterial culture. To determine whether dipstick or microscopy results reliably predicted the presence or absence of a reportable urinary pathogen we performed dipstick testing and phase contrast microscopy on unspun urine from 500 specimens. We also investigated the relationship between the presence of squamous epithelial cells (SECs) and mixed growth on culture.

METHODS

For each specimen, the presence of leukocyte esterase and urinary nitrite was recorded as well as the quantity of leukocytes (WBC), SECs, and erythrocytes. All cultures had the number and type of each organism recorded. Pyuria was defined as > or =10 WBC/mm(3).

RESULTS

Specimens with <10 SEC/mm(3) had fewer isolates (0.9 isolate per culture) than specimens with > or =10 SEC/mm(3) (two isolates per culture); therefore, SEC contamination was defined as > or =10 SEC/mm(3). Of 500 specimens, 266 (53%) had no growth and 136 (27%) had mixed growth. A total of 288 (58%) specimens had negative dipstick results and completely normal microscopy. Of these, 11 (4%) had a pure growth of a urinary pathogen but the pathogen was present in only three (1%) at > or =10(5) CFU/mL. Of 413 urine specimens without SEC contamination, 323 (78%) had either no detectable growth or pure growth compared with only 41 of 87 (47%) with SEC contamination (P<0.001). Of the 413 urine specimens without SEC contamination, 90 (22%) had > or =2 organisms compared with 46 of 87 (53%) with contamination (P<0.01). Pyuria was present in only 21 of 266 (8%) urine specimens without growth but was present in 60 of 95 (64%) specimens containing a reportable pathogen (P<0.01).

CONCLUSIONS

SEC contamination does not reliably predict cultures with mixed growth, urine specimens with negative dipstick results and microscopy rarely contain a reportable urinary pathogen, and screening algorithms are warranted and justified.

Measurement of cystatin-C and creatinine in urine

BACKGROUND

The concentration of serum cystatin-C (Cys-C) is highly correlated with creatinine (Cr), and is mainly determined by glomerular filtration; thus, Cys-C may be an index of the glomerular filtration rate (GFR). However, the kinetics of urinary Cys-C and Cr excretions are unclear. Thus, we investigated the kinetics of urinary Cys-C and Cr excretions, and examined whether the urinary Cys-C concentration can be used as a marker of renal function.

METHODS

The urinary excretion of Cys-C and Cr was evaluated in 1670 healthy subjects and 217 patients with proteinuria. We also investigated the urinary Cys-C concentration in 52 patients with chronic renal failure.

RESULTS

There was a good correlation between the urinary concentrations of Cys-C and Cr in the healthy group. This relation was also observed in patients showing persistent proteinuria without tubular cell damage. The mean urinary Cr concentration increased with age, and it was affected by the muscle mass. In contrast, the urinary Cys-C concentration was not affected by the muscle mass, and the concentration remained constant for all ages. We further found that the ratio of Cys-C to Cr (CCR) is a good index of the state of Cys-C reabsorption in the proximal tubules.

CONCLUSIONS

The urinary CCR can be a marker of renal tubular dysfunction. In addition, when CCR was in the normal range, the urinary Cys-C concentration accurately reflected the glomerular filtration function.

Bacteriological safety and cost-effectiveness of a nonrefluxing valve in the irrigation system during outpatient flexible cystoscopy

OBJECTIVE

To critically evaluate the infection rate associated with the use of a nonrefluxing irrigation system for outpatient flexible cystoscopy, by comparing it with conventional irrigation systems, and to determine the costs and benefits of this system of irrigation delivery.

PATIENTS AND METHODS

All patients undergoing flexible cystoscopy on scheduled outpatient lists were considered for inclusion in the study; 143 patients of 220 undergoing cystoscopy fulfilled the study criteria. The study group of patients underwent cystoscopy with a new single-use nonrefluxing valve inserted into the same irrigation delivery system that was used for the whole endoscopy session, and the control group had the complete irrigation system changed after each endoscopic examination. Midstream urine samples were taken for analysis before cystoscopy and again 3-4 days later. Infection was defined as a pure growth of >/= 105 organisms/mL, with associated pyuria defined as >/= 10 pus cells per high power microscopic field.

RESULTS

Complete data were available on 133 patients, with a further nine being excluded from the statistical analysis because they had a pre-existing urinary tract infection, leaving 64 patients in the study and 69 in the control groups. The overall infection rate for flexible cystoscopy was 3.2%, with no significant difference between the study and control groups. Cost savings of > 35% can be expected using the nonrefluxing valve method of irrigation delivery.

CONCLUSION

The nonrefluxing valve caused no detectable increase in patient morbidity from bacterial infection when compared with conventional irrigation systems for flexible cystoscopy, and can save considerable costs.

[Evaluation of pyuria by means of urinary sediment method--a comparison to the counting chamber method]

We compared the urinary sediment method to counting chamber method in evaluating pyuria, in order to elucidate an issue of urinary sediment method. The KOVA system was used for counting chamber method. Three hundred and ten urine specimens from the patients who visited Fuji City Central Hospital in March, 1995, were employed. The numbers of leukocytes of each specimen was counted by means of urinary sediment method and counting chamber method, and compared. The urinary leukocyte count evaluating by means of these two methods were correlated well. However, the discrepancy of urinary leukocyte counts by means of these two methods were recognized in two specimens. In these two specimens, the leukocyte count was 1 to 4/5HPF by means of urinary sediment method, but more than 50/microliter by means of counting chamber methods. Significant bacteria (10(4) cfu/ml or more), positive esterse reaction, and high pH (8.5) were recognized in both specimens. In addition, one of two these specimens was hypotonic (specific gravity was 1.008). Therefore, it was suggested that leukocytes were sometimes disrupted with centrifugation. These results indicate that counting chamber method is more useful urinary sediment method to detect pyuria.

Evaluation of urinary IL-1alpha and IL-1beta in gravid females and patients with bacterial cystitis and microscopic hematuria

OBJECTIVES

to determine IL-1alpha and IL-1beta levels in patients with bacterial cystitis, microscopic hematuria, and gravid females relative to a control group of normal subjects.

METHODS

enzyme immunoassays were used to measure concomitantly urinary IL-1alpha and IL-1beta in clean catch urine samples from normal subjects (n = 31) and study patients (n = 46). All normal subjects and patients underwent urinalysis, urine culture, and urine creatinine level determination. Since the IL-1alpha assay was developed for serum, the utility of the assay for urine specimens was unknown. The key parameters of urine collection, processing and sample storage for IL-1alpha were evaluated in detail.

RESULTS

mean values +/- SEM (pg/mg) for IL-1alpha/ Cr and IL-1beta/Cr were control group (0.25 +/- 0.10 and 0.17 +/- 0.06), bacterial cystitis (9.97 +/- 1.15 and 42.45 +/- 1.86), and microscopic hematuria (2.81 +/- 0.65 and 2.82 +/- 0.70). Differences in cytokine levels between the control group and patients with either bacterial cystitis or microscopic hematuria were statistically significant for both IL-1alpha/Cr (P < 0.026; P < 0.007, respectively) and IL-1beta /Cr (P < 0.0004; P < 0.014, respectively). IL-1beta/Cr correlates better with pyuria than IL-1alpha/ Cr (P = 0.02 vs P = 0.44). In gravid females, only IL-1alpha was significantly elevated relative to non-pregnant females (IL-1beta elevation approached statistical significance). Gravid females with positive urine cultures could not be distinguished from those with negative cultures based on either interleukin (P > 0.05).

CONCLUSIONS

Significant elevations of IL-1alpha and IL-1beta occur in patients with bacterial cystitis and microscopic hematuria. Correlation between pyuria and cytokine elevation was stronger for IL-1beta than for IL-1alpha. Changes in IL-1alpha may reflect changes in the bladder epithelium rather than in the inflammatory leukocytes. The ability of IL-1alpha and IL-1beta to serve as markers for bacterial cystitis in gravid females is diminished due to high basal levels during pregnancy.

Levels of inhibitors of tumor necrosis factor alpha and interleukin 1beta in urine and sera of patients with urosepsis

The antiinflammatory cytokine response during urosepsis was determined by measurement of concentrations of soluble tumor necrosis factor receptor (sTNFR) types I and II, interleukin 1 receptor antagonist (IL-1ra), soluble IL-1 receptor type II (sIL-1RII), and interleukin 10 in sera and urine of 30 patients with culture-proven urinary tract infections before and 4, 24, 48, and 72 h after initiation of antibiotic therapy and in 20 healthy individuals. In serum, the levels of sTNFR types I and II, IL-1ra, and IL-10 were higher in patients than in controls. In urine, only sTNFR type I and II levels were elevated in patients. The ratios of concentrations of both types of sTNFR in urine to concentrations in serum were higher in patients than in controls. These findings indicate that during urosepsis, the antiinflammatory cytokine response is generated predominantly at the systemic level.

Low bacterial counts in infants with urinary tract infection

We analyzed the number of colony-forming units in urine cultures obtained by suprapubic aspiration in a group of 366 unselected infants with symptomatic urinary tract infection to relate these findings to factors such as pyuria and vesicoureteric reflux. Seventy-three (20%) of 366 infants had fewer than 100,000 colony-forming units per milliliter. Such low counts were significantly related to low numbers of leukocytes in the urine. Vesicoureteric reflux was equally distributed among children, irrespective of the number of bacteria in quantitative culture. The findings emphasize the importance of sampling technique; in infants, the method of choice is suprapubic aspiration, or catheterization, which eliminates the risk that urinary tract infection is overlooked because of low bacterial counts.

Urinalysis. When--and when not--to order

Although routine urinalysis is common, the results are important in management of only certain diseases. Screening urinalysis to detect asymptomatic bacteriuria is recommended in adults 60 years of age or older, diabetic patients of any age, pregnant women, and adolescents. A positive result for protein on dipstick urinalysis should be evaluated in conjunction with other clinical and laboratory data (eg, the patient's age, physical findings, renal function, results of microscopic urinalysis). Evaluation of hematuria should always include dipstick analysis and microscopic examination of urine. Diabetes screening is best done with measurement of plasma glucose levels. Other available urinalysis tests include measurement of pH, specific gravity, ketones, bilirubin, and urobilinogen. In patients with renal or urinary tract disease, microscopic examination of urinary sediment is important.

Urine microscopy on a counting chamber for diagnosis of urinary infection

Several quantitative methods of urine microscopic examination for bacteriuria and pyuria on a blood cell counting-chamber have been found reliable for the diagnosis of urinary tract infection (UTI). However, no one technique has become popular or widely used because of laborious procedures associated with the method. We investigated the usefulness of microscopic examination of uncentrifuged urine on disposable counting-chambers. A total of 89 urine samples were obtained from 53 children (24 male and 29 female). Urine samples were examined for bacteriuria and pyuria using a disposable counting chamber and its reliability was analyzed in predicting significant bacteriuria defined by routine urine culture. Significant bacteriuria was diagnosed in 23 of 89 urine samples by urine culture. Microscopic urine examination on disposable counting-chambers was very easy without the need to set up or wash chambers and provided immediate information. Urine bacterial concentration determined by the counting-chamber method was closely correlated to that determined by bacterial culture. The counting-chamber method identified bacteriuria correctly in 21 of 23 urine samples diagnosed as significant bacteriuria (sensitivity = 91%) and also gave a correct diagnosis of 64 of 66 urine samples with non-significant bacteriuria (specificity = 98%). Nineteen of the 23 urine samples with significant bacteriuria also had pyuria. The positive predictive value of concomitant bacteriuria and pyuria was 100%. When neither bacteriuria nor pyuria was found, the negative predictive value was 100%. It was concluded that urine microscopy using disposable counting chambers was very easy, inexpensive, quick and reliable and thus an extremely useful method for diagnosing UTI.

Eosinophils in urine revisited

The finding of eosinophils in the urine has been suggested to be useful in establishing the diagnosis of acute interstitial nephritis (AIN). The diagnostic accuracy of this test has not yet been defined. It is the purpose of this study to define the specificity, sensitivity, and the predictive positive and negative values for the presence of eosinophils in the urine. One hundred forty-eight patients with pyuria were tested for the presence or absence of urinary eosinophils. In this group consecutively admitted to the hospital with WBC in the urine, 4% of patients had urinary eosinophilia of greater than 1 eosinophil per 100 cells. Since none of this group had the diagnosis of AIN, the false positive rate was 4% and the specificity was 96%. In a selected group of patients in which the diagnosis of AIN was suspected by a nephrology consultant, urinary eosinophils were found in 6 of 15 patients with a confirmed diagnosis of AIN but were also found in 10 of 36 patients with another renal diagnosis. The sensitivity for eosinophiluria was 40% and the specificity was 72% with a positive predictive value of only 38%. We conclude that eosinophiluria is not an accurate test for the diagnosis of AIN. The false positive and negative rates are too high to confirm an AIN diagnosis.

Reliability of pyuria detection method

The reliability of two methods for the detection of pyuria was studied in a total of 106 urine samples obtained from patients with identifiable underlying urinary tract disease. The coefficient of variation (CV) was significantly higher in the microscopic than in the counting chamber method. The CV obtained with the use of the KOVA slide 10 grid, a disposable and less expensive counting chamber, was identical to that obtained with the Bürker-Türk counting chamber. Only 50% of the patients who were proven to have pyuria of > or = 5 WBCs/HPF by the microscopic method had significant bacteriuria of > or = 10(4) bacteria per ml of urine. On the other hand, 95% and 90% of the patients who were proven to have pyuria of > or = 10 WBCs/mm3 with the Bürker-Türk and Fuchs-Rosenthal counting chambers had significant bacteriuria. It was concluded that the counting chamber provides a reliable method for the detection of pyuria and is highly predictive for the presence of significant bacteriuria. The KOVA slide 10 grid is an acceptable alternative to the regular counting chamber.

Progression from asymptomatic to symptomatic urinary tract infection in patients with SCI: a preliminary study

The purpose of this prospective pilot study was to (1) evaluate the role of pyuria in predicting the progression from asymptomatic to symptomatic urinary tract infection (UTI) in spinal cord-injured patients who undergo sterile intermittent bladder catheterization and (2) evaluate the impact of treating asymptomatic UTI on this progression. Twenty hospitalized patients were randomized to either the treatment group (10 subjects) or the control group (10 subjects). Weekly urine samples were obtained for quantitation of bacterial growth and pyuria. Neither the level nor the trend of pyuria helped predict the imminent progression to symptomatic UTI. Thirty percent of patients in the treatment group developed symptomatic UTI vs 70 percent of patients in the control group; it took a significantly longer time for patients in the treatment vs control group to develop symptomatic UTI (median number of days: 72 vs 7, respectively; p < 0.003). Further analysis of the long-term impact of antibiotic treatment of asymptomatic UTI is warranted.

Prevalence of urinary tract infection in febrile infants

Urinary tract infection (UTI), a relatively common cause of fever in infancy, usually consists of pyelonephritis and may cause permanent renal damage. This study assessed (1) the prevalence of UTI in febrile infants (temperature > or = 38.3 degrees C) with differing demographic and clinical characteristics and (2) the usefulness of urinalysis in diagnosing UTI. We diagnosed UTI in 50 (5.3%) of 945 febrile infants if we found > or = 10,000 colony-forming units of a single pathogen per milliliter in a urine specimen obtained by catheterization. Prevalences were similar in (1) infants aged < or = 2 months undergoing examination for sepsis (4.6%), (2) infants aged > 2 months in whom UTI was suspected, usually because no source of fever was apparent (5.9%), and (3) infants with no suspected UTI, most of whom had other illnesses (5.1%). Female and white infants had significantly more UTIs, respectively, than male and black infants. In all, 17% of white female infants with temperature > or = 39 degrees C had UTI, significantly more (p < 0.05) than any other grouping of infants by sex, race, and temperature. Febrile infants with no apparent source of fever were twice as likely to have UTI (7.5%) as those with a possible source of fever such as otitis media (3.5%) (p = 0.02). Only 1 (1.6%) of 62 subjects with an unequivocal source of fever, such as meningitis, had UTI. As indicators of UTI, pyuria and bacteriuria had sensitivities of 54% and 86% and specificities of 96% and 63%, respectively. In infants with fever, clinicians should consider UTI a potential source and consider a urine culture as part of the diagnostic evaluation.

Application of a leukocyte and nitrite urine test strip to the management of children with neurogenic bladder

A urine leukocyte count of > or = 50/mm3 together with a bacterial count of > or = 10(5) colony-forming units (CFUs) per milliliter was used to define significant infection in 160 children with neurogenic bladder and evaluate the leukocyte and nitrite components of the Chemstrip 9 test. A Chemstrip 9 leukocyte reading of < or = 25 together with a negative nitrite reaction occurred in 99 children and had a sensitivity of 83.5% and a negative predictive value for infection of 97.0%. A Chemstrip 9 reading of > or = 500 leukocytes together with a positive nitrite reaction occurred in 18 children and had a sensitivity of 40% with a 100% positive predictive value for infection. Other combinations of Chemstrip 9 leukocyte and nitrite reactions were unhelpful or of uncertain value. Selection of up to three specimens from each patient increased the number of samples to 360 and provided general confirmation of the above conclusions. Nitrofurantoin may reduce the sensitivity of the nitrite strip reaction.

Does residual urine predispose to urinary tract infection?

The relationship between the presence of post-micturition residual urine and urinary tract infection is unclear. We have performed a retrospective analysis of 342 studies on bladder emptying and compared the incidence of bacterial infection and pyuria in patients with residual urinary volumes of more or less than 100 ml. In patients with a residual volume > 100 ml 49/219 studies showed evidence of pyuria and 28/198 studies of patients whose residual urine was less than 100 ml showed evidence of infection. In cases where the residuals were > 100 ml 33/123 had evidence of pyuria and 19/109 infection. There was no significant increase in the rate of infection in patients with large residual urinary volumes, suggesting that there is no definite correlation between post-micturition residues and urinary tract infection.

The dipstick test in the diagnosis of UTI and the effect of pretreatment catheter exchange in catheter-associated UTI

We examined the value of the dipstick test for detecting pyuria and bacteriuria in the diagnosis of urinary tract infection (UTI). The dipstick esterase test could be quickly assessed and could easily detect leukocyte esterase in the urine. This was well correlated with the conventional sedimentation method. The dipstick nitrate reduction method for detecting bacteriuria, however, was not well correlated with the urine culture method. These findings suggested that the dipstick esterase test was a useful method for detecting pyuria in the diagnosis of UTI, but not the dipstick nitrate reduction method. Catheter-associated UTI is the most difficult category of UTI to treat and control. One of the reasons for this is the formation of biofilm around the indwelling catheter. We attempted to evaluate the effect of catheter exchange just before treatment of catheter-associated UTI with either 300 or 600 mg/day of levofloxacin, one of the newer quinolones. However, we are unable to find any apparent effect on the drug's efficacy.

[Usefulness of dipstick test for determining leukocytes and bacteria in urine]

The value of a simple dipstick test (BMtestLN, Boehringer Mannheim-Shionogi) for determination of leukocytes and bacteria in urine was examined. This test consisted of detection of esterase, an enzyme present in leukocytes and the nitrate reduced by bacteria. A total of 666 clinical urine specimens were tested with both tests. The evaluation of leukocytes in urine was compared with microscopic examination, and the identification and measurement of strains was performed using a semiquantitative plate culture method as a reference. The leukocyte esterase test had a sensitivity of 85.3%, a specificity of 67.3%, positive predictive value of 54.7% and negative predictive value of 90.8%. The range of the sensitivity value of nitrate test was 25.7% for the detection of bacteriuria (bacteria greater than or equal to 10(4) CFU/ml). This test had a specificity of 99.6%, positive predictive value of 94.8% and negative value of 82.9%. We concluded that this dipstick test is not useful for determination of the slight change of pyuria, but sensitive for the determination of acute and untreated urinary tract infections.

Presence of platelet-activating factor in pyuria in humans

The relationship between the occurrence of platelet-activating factor (PAF) and neutrophils in urine from patients with urinary tract infection was examined. PAF was detected in human pyuria, when leukocyte levels reached at least 300 cells/microL (n = 45), but not in normal urine (n = 12). The amount of PAF found in pyuria, measured by platelet aggregation assay, was 0.01 to 13.3 pmol/mL. A close correlation was seen between the amount of PAF present and the number of urinary leukocytes (p less than 0.01, r = 0.70). The leukocytes in pyuria consisted almost entirely of neutrophils (96 +/- 4%, mean +/- S.D.). Our findings suggest that the occurrence of PAF is associated with the accumulation of neutrophils in urine.

Efficacy of routine admission urinalyses in psychiatric hospitals

The clinical efficacy of routine admission urinalyses was evaluated in 515 patients admitted to a psychiatric hospital. Two staff psychiatrists reviewed the patients' charts to determine which test resulted in diagnostic or therapeutic management changes. Abnormalities were found in 40 (7.8%) of the cases, but only four (0.8%) of the routine urinalyses affected patient therapy. It is concluded that routine admission urinalysis has very little impact on the care of psychiatric patients and that there is little justification for ordering this test on all patients admitted to psychiatric hospitals.

Home-voided urine specimens in women. Diagnostic agreement with clean-catch midstream specimens

One hundred and fifty women who brought a home-voided urine sample to a general practitioner were asked at the same consultation to provide another sample under controlled conditions. Seventy-three women had lower urinary tract symptoms and 77 were asymptomatic. The two samples were analysed for pyuria (greater than or equal to 5 leucocytes/HPF) and bacteriuria (greater than or equal to 10(4) v. greater than or equal to 10(5) cfu/ml). The agreement when diagnosing pyuria and bacteriuria was estimated by Kappa (K). The home-voided sample was taken with adequate sampling technique by only 12% of women. Moreover, its bladder incubation time was twice that of the surgery sample (5.4 h v. 2.4 h). There was, however, no difference in the distribution of pyuria or bacteriuria between the paired samples. Agreement, which was high for the diagnosis of pyuria (K = 0.80), was significantly lower for the diagnosis of bacteriuria (K = 0.52, P less than 0.01). A home-voided sample seems sufficient in the diagnosis of the dysuria-pyuria syndrome in women.

Urine screening for leucocytes and bacteria by dipstick and reflectance spectrophotometry

In order to develop a rapid and reliable method for screening large numbers of urines for leucocytes and bacteria a dipstick method was used with colorimetric reading of colour changes with a reflectance spectrophotometer. One thousand consecutive urine specimens were tested by that method using a single dipstick for leucocyte esterase, nitrite, blood and protein in parallel with routine methods for enumeration of leucocytes by microscopy and quantitative culture for bacteria. Results of the four dipstick tests taken together had predictive values of 83.7% for a positive test for evidence of infection and 97.2% for a negative result. The false negative rate was 1%. Of the 191 urines with a significant bacteriuria (greater than 10(5) organisms/ml), 10 were false negatives by dipstick testing, representing 5% of all infected urines. Elimination of the need for culture on specimens that were negative by all four tests would reduce the workload by 36%.

Clinical correlates of eosinophiluria

We assessed the clinical correlates of eosinophils in the urine in 65 patients. In 16% of 470 patients whose urine was specifically examined, eosinophils were noted in the urine sediment. Review of the 65 patients with eosinophiluria demonstrated that when eosinophils were expressed as a percentage of total urine white blood cells, 85% (55/65 patients) had less than 5% urine eosinophils and 45% (29/65 patients) had less than 1%. Infection of the upper and lower urinary tract accounted for 45% of the clinical conditions associated with eosinophiluria. In nine (14%) of the 65 patients a diagnosis of acute interstitial nephritis could be made by clinical criteria or from renal biopsy specimens. We conclude that the finding of urine eosinophils is associated with a variety of clinical conditions and may be most useful when expressed as a percentage of total white blood cells in the urine. At a low-percentage positive (less than 5%), it may not be a good predictor of acute interstitial nephritis, but at a higher level (greater than 5%) it may be a more valuable predictor.

[Bacteria and leukocyte count in the urine in the diagnosis of urinary tract infections]

The count of bacteria in fresh, unstained, uncentrifuged urine specimens, using a phase-contrast microscope, magnification X400, and a hemocytometer chamber, is a simple method to exclude urinary tract infection. The specificity of this method is 94%, while the sensibility is 66%. We exclude an urinary infection when the count is less than 5 bacteria/0.1 ml. If we add to bacteria the evaluation of pyuria, the sensibility of this method does not change. On the contrary what we observe is an increase of the false positives. Bacteria more easily identified in urine specimens are E. Coli and Klebsiellae; the bacterioscopy has confirmed respectively 82% and 100% of positive urinecultures. The corresponding values for Protei and Streptococci are 23% and 20% respectively. This method is very simple also for teaching; it requires only a few minutes and is inexpensive. Its most useful utilization is the exclusion of urinary tract infection when the concentration of bacteria in the urine is less than 5 bacteria/0.1 ml.

Fastidious bacteriuria and pyuria

Mid stream specimens of urine that showed pyuria or bacteriuria on direct microscopy and no bacterial growth on initial routine culture were collected from 346 patients. These specimens were cultured for the presence of fastidious organisms using two different test systems. One system used non selective media and the other used selective media. Any fastidious organism isolated was identified by standard methods. Lactobacilli were the only fastidious organisms isolated in significant numbers. Using comparable test systems, equivalent numbers of Lactobacilli were isolated from both test and control group and because of the difficulty in specimen collection, these are to be considered as possible contaminants.