Can routine automated urinalysis reduce culture requests?

ObjectivesThere are a substantial number of unnecessary urine culture requests. We aimed to investigate whether urine dipstick and microscopy results could accurately rule out urinary tract infection (UTI) without urine culture.Design and methodsThe study included a total of 32 998 patients (11 928 men and 21 070 women, mean age: 39 ± 32 years) with a preliminary diagnosis of UTI and both urinalysis and urinary culture were requested. All urine cultures were retrospectively reviewed; association of culture positivity with a positive urinalysis result for leukocyte esterase (LE) and nitrite in chemical analysis and pyuria (WBC) and bacteriuria in microscopy was determined. Diagnostic performance of urinalysis parameters for detection of UTI was evaluated.ResultsIn total, 758 (2.3%) patients were positive by urine culture. Out of these culture positive samples, ratios of positive dipstick results for LE and nitrite were 71.0% (n = 538) and 17.7% (n = 134), respectively. The positive microscopy results for WBC and bacteria were 68.2% (n = 517) and 78.8% (n = 597), respectively. Negative predictive values for LE, nitrite, bacteriuria and WBC were very close to 100%.ConclusionsMost of the samples have no or insignificant bacterial growth. Urine dipstick and microscopy can accurately rule out UTI. Automated urinalysis is a practicable and faster screening test which may prevent unnecessary culture requests for majority of patients.     

Cost-effective screening by nursing staff for urinary tract infection in the spinal cord injured patient

Screening tests for urinary tract infections (UTI) are used in the clinical laboratory setting. This study evaluated the efficacy of screening by nursing staff on the inpatient unit, instead of the clinical laboratory, in the spinal cord-injured population. Fifty-three consecutive traumatically spinal cord-injured patients had weekly urine collection, except when infected or on antibiotics. Each urine sample was tested by a nitrite and leukocyte esterase (LE) dipstick (Chemstrip LN by Bio-Dynamics) and by routine clinical laboratory culture. A total of 169 tests were completed. The correlation coefficients of the LE and the nitrite tests with the culture were 0.604 (P less than 0.001) and 0.663 (P less than 0.001), respectively. The correlation of the combined tests was 0.837 (P less than 0.001). The sensitivity, specificity and positive and negative predictive values of nitrite-LE testing by nursing staff were calculated and compared favorably with published performances of clinical laboratory staff. When measured against the culture, the combined nitrite and LE test had a sensitivity of 79%, specificity of 99% and positive and negative predictive values of 96% and 95%, respectively. The use of a protocol where laboratory culture is performed only when the dipstick test is positive, would reduce the number of cultures by 83%. After extra costs of the additional screen are added, the use of dipstick screening methods by nursing staff can reduce the cost of weekly urine screening by 73%, with a false negative rate of only 4.4%. The expense and complexity of screening for UTI is reduced, response time is minimized and laboratory cultures will have a higher probability of useful clinical information.     

尿流式有形成分及干化学分析在尿路感染诊断中的应用评价

目的 评价尿干化学分析及UF-1000i流式尿有形成分分析单独及联合应用时在尿路感染诊断中的应用价值.方法 留取148例尿路感染(UTI)患者、284例非尿路感染患者的中段尿标本,分别用培养法做尿细菌计数和鉴定,用UF-1000i流式尿有形成分分析仪做细菌计数(BACT)、酵母样菌(YEC)、WBC检测,用URISYS 2400尿干化学分析仪做自细胞酯酶(LEU)、亚硝酸盐(NIT)检测.评价尿干化学分析、UF-1000i流式尿有形成分分析仪以及UF-1000i联合尿干化学分析与定量尿细菌培养对诊断UTI的一致程度,并评价其对UTI诊断的敏感度、特异度、阳性预测值、阴性预测值、准确度.结果 在148例尿路感染患者中,定量尿细菌培养的检出率为73.6%(109/148),尿干化学分析LEU和NIT同时为阳性的检出率为26.4%(39/148),两种方法的检出率之间差异有统计学意义(χ2=55.68,P<0.05).UF-1000i流式尿有形成分分析BACT和WBC任意1项为阳性诊断UTI的检出率为91.2%(135/148),高于定量尿细菌培养的检出率,差异有统计学意义(χ2=14.70,P<0.05).UF-1000i流式尿有形成分分析和尿干化学分析仪联合参数BACT、WBC、LEU和NIT任意1项为阳性诊断UTI的检出率为94.6%(140/148),高于定量尿细菌培养的检出率,差异有统计学意义(χ2=20.45,P<0.05).尿干化学分析敏感度较低,为26.4%(39/148),特异度较高,为99.3%(282/284);应用UF-1000i流式尿有形成分分析BACT作为尿路感染诊断依据时的敏感度为92.6%(137/148),特异度为39.8%(113/284),阳性预测值为44.5%(137/308),阴性预测值为91.1%(113/124);尿干化学分析与UF-1000i流式尿有形成分分析联合应用时,敏感度为98.O%(145/148),阴性预测值97.1%(100/103),特异度为35.2%(100/284),阳性预测值为44.1%(145/329),准确度为56.7%(245/432).结论 联合UF-1000i流式尿有形成分分析及尿干化学分析可在早期尿路感染筛查诊断中发挥重要作用;同时对尿细菌培养为阴性的UTI患者的明确诊断具有重要价值.     

尿干化学和尿流式检测结果快速预测肾结石患者尿路细菌感染模型的建立与评价

目的 建立一种可以通过尿干化学和尿流式检测结果预测肾结石患者尿路感染(UTI)的方法.方法 分析414例肾结石患者的清洁中段尿样本,将尿流式细菌计数和亚硝酸盐、白细胞酯酶尿干化学检测结果与中段尿培养结果进行比对,确定阈值.结果 尿流式细菌计数为231.8/μL时,检测敏感性为73.97％、特异性为91.14％.亚硝酸盐...     

Rapid screening and microbiologic processing of pediatric urine specimens

Urinary nitrite and leukocyte esterase dipstick tests were evaluated as rapid screening procedures to select probable culture-positive urines for direct identification (AutoMicrobic System urine cards) and modified Kirby-Bauer susceptibility testing. Approximately 73% of significant culture-positive (greater than 10(5) organisms per milliliter, pure culture) urine specimens could be selected by nitrite testing alone with very high specificity (approximately 99%). The leukocyte esterase test detected 85% of culture-positive urines when used alone and approximately 91% when used in combination with nitrite testing (if either test was positive it was considered a positive screening); however, the esterase test was significantly less specific for bacteriuria than the nitrite test. Based on these results, the nitrite test was selected for use as the screening test. Rapid, direct identification and susceptibility tests on screen-positive urines showed 97% correlation with standard testing methods. Significant positive urines processed in this manner could be reported with quantitation, identification, and susceptibility results within 24 hr.     

Bacteriuria detection with a urine dipstick applied to incontinence pads of nursing home residents

The purpose of this study was to evaluate a new method of initial on-site evaluation of bacteriuria in an incontinent nursing home population. Nitrite and a composite of nitrite and/or leukocyte esterase results of the new method were compared with clean-catch urine culture results of each participant to determine sensitivity, specificity, positive and negative predictive values, and efficiency. These findings were compared with results of the traditional dipstick urinalysis for bacteriuria assessment. The new method was as effective as the traditional method in assessing both the presence and absence of bacteriuria. Results of this study indicate the new dipstick/pad method may assist in the assessment of bacteriuria in incontinent nursing home residents.     

Screening for bacteriuria with the LN strip test

Recently, the LN strip test was introduced for purposes of rapid screening of urine specimens for bacteriuria. The LN strip test permits detection of urinary leukocyte esterase and nitrite. A total of 2,481 unselected urine specimens from three tertiary care hospitals were examined using the LN strip test and the results were compared with those obtained with a conventional quantitative culture technique. When the results of the leukocyte esterase and nitrite tests were combined, the sensitivity and specificity of the LN strip test were 88.8% and 71.3%, respectively, based on culture results of greater than or equal to 10(5) CFU/ml. Test sensitivity decreased at greater than or equal to 10(4) CFU/ml, whereas test specificity increased.     

Evaluation of dipstick tests and reflectance meter for screening for bacteriuria in elderly patients.

When screening for bacteriuria in 615 elderly people was compared to standard methods of bacterial culture, the Ames Multistix 10 dipstick was more effective than the BM Test 7. Tests for nitrite and leucocyte esterase on the Multistix 10 had a higher sensitivity and specificity than tests for blood and protein only. Using a reflectance meter increased the sensitivity of the Multistix 10 to 80.6%. Of five common urinary symptoms only incontinence was significantly more frequent in patients with bacteriuria.     

Comparison of three automated urinalysis systems--Bayer Clinitek Atlas, Roche Urisys 2400 and Arkray Aution Max for testing urine chemistry and detection of bacteriuria

BACKGROUND: Our study is aimed to determine the performance of 3 automated urinalysis systems-Clinitek Atlas, Urisys 2400 and Aution Max. METHODS: One thousand urine specimens were analyzed with the 3 automated systems. The results of the 3 assays were compared for testing urine chemistry and evaluating the capacity of leukocyte esterase and nitrite to detect bacteriuria. RESULTS: The correlation between the 3 instruments represented as within 1 grading difference was better between the Atlas and Aution Max systems for pH, blood, glucose, urobilinogen, ketone and specific gravity. For protein and nitrite, better correlation was observed between the Atlas and Urisys 2400, while the Aution Max and Urisys 2400 conveyed better correlation for bilirubin and white blood cells. The sensitivity and specificity of both the leukocyte esterase and nitrite in screening for significant bacteriuria were 71.7, 58.9, 70.8% and 99.1, 99.1 and 97.2%, for the Clinitek Atlas, Aution Max and Urisys 2400, respectively. CONCLUSIONS: The automated urinalysis systems demonstrate acceptable correlations with each other in urine chemistries, especially between the Clinitek Atlas and Aution Max systems on the majority of items. The specificity and negative predictive value of leukocyte esterase and nitrite of the 3 instruments for screening of significant bacteriuria were sufficient to avoid unnecessary urine culture.     

Rapid urinalysis assays for the diagnosis of urinary tract infection

Urinary tract infection (UTI) in premenopausal women is a frequent complaint in general practice. UTI is usually diagnosed on the basis of clinical symptoms and the use of one or more laboratory tests, the most common being rapid urinalysis reagent assays (urine dip) or midstream urine culture. In order to correlate the leucocyte esterase results of a rapid urinalysis assay with direct urine microscopy for pyuria, undiluted non-centrifuged urine samples from 206 volunteer female healthcare professionals were subjected to analysis using direct urine microscopy using a counting chamber and a rapid urinalysis assay. Of the 206 specimens, 74 were positive for leucocyte esterase using the rapid urinalysis assay, and 39 specimens demonstrated significant pyuria (greater than or equal to 10 leucocytes/microl) on direct microscopy. When the leucocyte esterase results were correlated with the direct urine microscopy results, an assay reading of 15 leucocytes/microl ('trace' on the visual scale) had a sensitivity of 91%, specificity of 79%, positive predictive value of 53% and a negative predictive value of 97%. An assay reading of 25 leucocytes/microl ('+' on the visual scale) or greater had a sensitivity of 63%, specificity of 95%, positive predictive value of 75% and a negative predictive value of 91%. In premenopausal, non-pregnant females, a rapid urinalysis assay result of 25 leucocytes/microl or greater will predict significant pyuria on urine microscopy with reasonable confidence, thereby reducing the need for more costly urine cultures.     

Urinary tract infection in children

Up to 7 percent of girls and 2 percent of boys will have a symptomatic, culture-confirmed urinary tract infection by six years of age. Urinary tract infection may be suspected because of urinary symptoms in older children or because of fever, nonspecific symptoms, or failure to thrive in infants. Urine dipstick analysis is useful for ruling out urinary tract infections in cases with low clinical suspicion. However, urine culture is necessary for diagnosis of urinary tract infections in children if there is high clinical suspicion, cloudy urine, or if urine dipstick testing shows positive leukocyte esterase or nitrite activity. Despite current recommendations, routine imaging studies (e.g., renal ultrasonography, voiding cystourethrography, renal scans) do not appear to improve clinical outcomes in uncomplicated urinary tract infections. Oral antibiotics are as effective as parenteral therapy in randomized trials. The optimal duration of antibiotic therapy has not been established, but one-day therapies have been shown to be inferior to longer treatment courses.     

EVALUATION OF DIPSTICK TESTS AND REFLECTANCE METER FOR SCREENING FOR BACTERIURIA IN ELDERLY PATIENTS

SUMMARY When screening for bacteriuria in 615 elderly people was compared to standard methods of bacterial culture, the Ames Multistix 10 dipstick was more effective than the BM Test 7. Tests for nitrite and leucocyte esterase on the Multistix 10 had a higher sensitivity and specificity than tests for blood and protein only. Using a reflectance meter increased the sensitivity of the Multistix 10 to 80.6%. Of five common urinary symptoms only incontinence was significantly more frequent in patients with bacteriuria.     

Evaluation of the Coral UTI Screen system for rapid automated screening of significant bacteriuria in a regional centralized laboratory

An evaluation of the Coral UTI screen system (Coral Biotechnology, San Diego, CA) compared to urinalysis/urine culture was done to assess its performance for rapidly screening a high volume of urine samples for significant bacteriuria in a regional central microbiology laboratory. A total of 1094 urine samples from ambulatory patients were evaluated. 670 (61.2%) urine samples were negative or positive [178 (16.3%)] by both methods. 217 (19.8%) other samples were UTI screen positive but had either no growth or no uropathogens on culture; 9 of these samples were possibly false negative by culture because of the presence of pyuria, indicating the presence of either a urinary tract infection or another inflammatory process. Another 29 (2.7%) samples had false negative screens because the urine culture was positive, but only 5 of these patients were treated with antibiotics after urine specimen collection. Overall, the Coral UTI screen has a sensitivity of 86.0%, a specificity of 75.5% and a positive and negative predictive value of 45.0% and 95.9% respectively. Routine use of the UTI screen would allow same day reporting of 65% of all urine culture results without having to proceed to culture.     

The uncertainties of the diagnosis and treatment of a suspected urinary tract infection in elderly hospitalized patients

ABSTRACT

Introduction: The diagnostic criteria for a urinary tract infection (UTI) and proper treatment of elderly patients hospitalized with nonspecific symptoms is uncertain.

Areas covered: A nonsystematic literature review of the variable approaches in diagnosing and treating hospitalized elderly patients with a suspected UTI.

Expert commentary: Bacteriuria and/or pyuria cannot confirm the diagnosis of a UTI because of the high prevalence in the elderly regardless of presentation so urine cultures are not indicated in those hospitalized for diseases outside the urinary tract. The microscopic urinalysis is imprecise and inaccurate, and lowers the sensitivity in detecting a bacteremic UTI if used to confirm a positive dipstick test result. There is some evidence that cancelling urine cultures in the absence of a positive dipstick (negative leukocyte esterase and nitrite) is safe and prevents unnecessary antibiotic therapy. Urinary catheterization to obtain a urine sample is common in the elderly and it is unclear if changes in antibiotic therapy based on culture results outweighs the risks of the procedure. In hospitalized elderly patients without septic shock, it is unclear when it is safe to withhold antibiotic therapy, and when patients with criteria used to define severe sepsis need immediate treatment with broad-spectrum antibiotics.     

An evaluation of a leukocyte esterase/nitrite test strip and a bioluminescence assay for detection of bacteriuria

A leukocyte esterase/nitrite (Chemstrip LNTM) and a bioluminescence assay (LumacTM) were evaluated for detection of bacteriuria in 1,000 urine specimens. Both devices provided high predictive negative values (95.4-97.8%); however, false-negative values at levels of bacteriuria greater than or equal to 10(4) CFU/ml were 22.6% and 12.3%, respectively, for the leukocyte esterase/nitrate and the bioluminescence assay tests. The corresponding false-negative values at levels of bacteriuria of greater than or equal to 10(5) CFU/ml were 16.5% and 3.9%, respectively.     

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%.     

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.     

Correlation of urinalysis and dipstick results with catheter-associated urinary tract infections in surgical ICU patients

Objective To determine the utility of urinalysis and dipstick results in predicting urinary tract infections in catheterized ICU patients.Design and setting Urine samples were collected for 4 months from patients admitted a ten-bed surgical ICU of an urban public teaching hospital designated by the state of New York as a level I trauma center. The correlation was analyzed between urinalysis and dipstick results from urine samples and subsequent quantitative culture results.Patients All patients with indwelling urinary catheters admitted to the ICU were considered eligible; 106 patients were enrolled, and 300 individual urine samples were analyzed.Measurements and results There were 44 catheter-associated urinary tract infections. Nitrite presence was the best indicator of infection (91.8% specificity) but was not a reliable clinical test due to a sensitivity of 29.5% and positive and negative likelihood ratios of 3.52 and 0.56, respectively. None of the other parameters (leukocyte esterase, white blood cell count, urobilinogen, presence of yeast or bacteria) were independently correlated with the culture results either individually or in combination.Conclusions Based on our data we cannot recommend the use of urinalysis or dipstick in screening for potential catheter-associated urinary tract infections.     

UF-1000i尿有形成分分析仪在尿路感染筛查中的应用评价

目的评价UF-1000i尿流式有形成分分析仪在尿路感染（UTI）筛查中的应用价值。方法应用UF—1000i尿流式有形成分分析仪检测148例疑似uTI患者中段尿标本中的细菌（BACT）数和白细胞（WBC）数,以定量尿细菌培养作为诊断UTI金标准,应用受试者工作特征（ROC）曲线确立阳性判断标准,评价UF-1000i尿流式有形成分分析仪诊断UTI的敏感性、特异性、阳性预测值、阴性预测值和准确性。结果UF—1000i尿有形成分分析仪BACT和WBC诊断UTI的cut—off值分别为325个／汕和48个／μL,其诊断UTI的敏感性、特异性、阳性预测值、阴性预测值、准确性分别是：78．3％、92．2％、81．8％、90．4％、87．8％和73．9％、81．4％、64．2％、87．4％、79．1％。UF—1000i联合诊断uTI的敏感性、特异性、阳性预测值、阴性预测值和准确性分别95．7％、70．6％、59．5％、97．3％、78．4％。结论UF．1000i尿有形成分分析仪可作为UTI的快速筛查工具。     

Validity of urinalysis and microscopy for detecting urinary tract infection in the emergency department.

This study assessed the validity of standard urinalysis, urinalysis for leucocyte esterase and nitrites, and urgent microscopy in the diagnosis of urinary tract infection (UTI) in 60 female patients with a triage diagnosis of UTI. There were 24 (40%) proven UTIs after culture. Simple urinalysis was sensitive for UTI (95.8%) but the positive predictive value was only 45.1%. The addition of leucocyte esterase and nitrite urinalysis testing did not improve the sensitivity, but if both of these were positive the positive predictive value improved to 100%. Urgent microscopy alone was sensitive (100%) but non-specific (38.9%). The specificity of the diagnosis improved to 94.4% for organism counts of >or=10/microl and to 88.9% for leucocyte counts of >or=50/microl. The negative predictive value of no detectable leucocytes on microscopy was 94.7%. Screening for UTI in the emergency department (ED) population is improved by the addition of leucocyte esterase and nitrite test. A positive urinalysis test for leucocytes and nitrites, or urinalysis positive at levels of >or=500 leucocytes or >or=5 g/l protein should confirm a clinical diagnosis of UTI. Urgent urine microscopy should be performed only if the above criteria are not met yet a minimum of one urinalysis result is positive.