Results of dipstick tests, visual inspection, microscopic examination of urine sediment, and microbiological cultures of urine compared for simplifying urinalysis

Using microscopic sediment examination, reagent dipsticks, visual appearance, and microbiological culture, we studied 196 urine specimens collected under sterile conditions. We conclude that the sensitivities and specificities noted in the comparison of dipstick urinalysis with urine microscopy justify eliminating many microscopic examinations if a procedural flowchart is used. All 33 (16.8%) of the uncontaminated urine specimens showing substantial potential pathogen content on culture had either a turbid appearance or positive results for one or more dipstick tests. A positive dipstick test result for nitrite most consistently indicated that the urine should be cultured.     

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%.     

尿干化学与流式细胞术联合用于尿液有形成分镜检筛选的研究与应用

目的 制定针对UF-1000i尿液分析流水线(由UF-1000i尿流式分析仪和AX-4030尿干化学分析仪组成)自动化检测结果的尿液镜检复检规则.方法 收集2009年9月至2010年2月解放军总医院尿液常规标本共2 839份.首先利用UF-1000i尿液分析流水线对2 839份尿液标本进行有形成分分析(包括RBC、WB...     

尿液分析试纸在腹水感染中的诊断价值

目的 研究尿液分析试纸在腹水感染中的诊断价值.方法 选择不同病因形成的腹水标本33例,应用尿液分析试纸对腹水标本进行白细胞检测,同时与手工计数法作比较,并作统计学分析.结果 尿试纸检验结果阳性率为54.5%,传统方法结果阳性率为57.6%.两种方法阳性率比较,差异无统计学意义(P>0.05).应用尿液分析试纸结果的敏感性78.95%,特异性78.57%,阳性预测值83.33%,阴性预测值73.33%,尿液分析试纸对诊断腹水感染的敏感性及特异性均较高.计算kappa值为0.57,尿液分析试纸与手工计数法两种方法一致性较好.结论 尿液分析试纸检测法具有快速、操作简单、结果比较可靠等优势,在临床上应用于腹水感染的初步筛检有一定的可行性.     

False-positive microhematuria in dipsticks urinalysis caused by the presence of semen in urine

OBJECTIVES: Positive readings of blood in dipstick urinalysis may indicate trauma or imbalance in hemostasis associated with drug treatment. We evaluated the possibility that the presence of semen in urine may cause false-positive hematuria. DESIGN AND METHODS: Semen specimens obtained from 25 healthy men were directly applied on urine dipsticks for evaluation of the presence of blood. Isolated sperm cells and seminal fluid were also tested. Dipstick analyses were further performed with semen samples diluted in normal urine.Four healthy male volunteers provided urine samples before and immediately after having had sexual relationships. These samples were dipstick tested for the presence of blood. RESULTS: Semen, spermatozoa and seminal fluid gave false positive results for microhematuria following direct application of samples on dipsticks as well as after their suspension in urine (p < 0.00001).Three out of four postcoital urine specimens yielded positive results for blood. CONCLUSIONS: In men, postcoital urine may be falsely "positive" for microhematuria. This may have implication on the management of male patients in emergency situations such as acute coronary syndromes.     

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.     

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.     

全自动尿沉渣分析仪在尿管型检测中的应用

目的探讨全自动尿沉渣分析仪在尿管型检测中的应用。方法收集尿管型患者晨尿标本836份。所有标本均经尿干化学分析仪检测Pro≥1＋或尿沉渣分析仪提示有管型。采用UF100全自动尿沉渣分析仪和显微镜检测管型,对比分析两者的检测结果。结果 836份标本中,UF100全自动尿沉渣分析仪检测阳性者320例,占38.28%;显微镜检测阳性者195例,占23.33%。其中UF100全自动尿沉渣分析仪的假阳性率为26.52%,假阴性率为23.08%。UF100尿沉渣分析仪与显微镜检测管型的阳性结果比较,差异有统计学意义（P〈0.01）。结论 UF100全自动尿沉渣仪能快速筛检尿沉渣,但存在一定的假阴性,必须同时将其检测结果与尿干化学结果结合考虑以决定是否再进行显微镜检测,减少假阴性以防止漏检。     

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.     

Dipstick screening for urinary tract infection before arthroplasty:a safe alternative to laboratory testing?

We performed a prospective study on 247 consecutive patients attending our arthroplasty pre-admission clinic over six months, to compare the accuracy of dipstick urinalysis with the standard microbiological test for excluding urinary tract infection. There were 22 positive culture results and 43 positive dipstick results, with 16 true positives and 198 true negatives. Sensitivity was 72.7%, lower then the 88.0% figure for specificity. The positive predictive value was 37.2%, and the negative predictive value was 97.1%. Dipstick urinalysis is ideally suited to the busy pre-admission setting and would have resulted in a 90% reduction in the number of samples sent for laboratory analysis. In view of these results, we have changed our working practise from performing cultures to dipstick urinalysis on all patients prior to arthroplasty.     

Squamous epithelial cell presence reduces accuracy of urinalysis for prediction of positive urine cultures

BackgroundDiagnostic value of urinalysis specimens contaminated with squamous epithelial cells (SEC) from the genital surfaces is assumed to be limited compared to clean-catch samples. However, no studies have quantified the change in predictive value in the presence of SECs for individual urinalysis markers.MethodsIn a retrospective, single center cohort study, we analyzed all urine cultures sent from the ED over a 26-month period with corresponding urinalysis results. Cultures were classified as positive with growth of >10⁴ colony forming units of pathogenic bacteria, negative if no growth, or contaminated for all other results. UA specimens were classified as contaminated or clean based on SEC presence. Accuracy of urinalysis markers for prediction of positive cultures was calculated as an area under the curve (AUC) and was compared between contaminated and clean UA specimens.Results6490 paired UA and urine cultures were analyzed, consisting of 3949 clean and 2541 contaminated samples. SEC presence was less common with male gender, older age, and smaller BMI. Urine cultures were 19.2% positive overall, and SECs were more common in contaminated cultures. AUCs for individual markers ranged from 0.557 to 0.796, with pyuria, bacteriuria, and leukocyte esterase having higher AUC in clean samples over contaminated.ConclusionAnalysis of AUC for individual urinalysis markers showed reduced diagnostic accuracy in the presence of SECs. SEC presence also reflected much higher rates of contaminated cultures. These results support the reduced reliance on contaminated UA specimens for ruling in UTI in ED patients.     

Urine polymerase chain reaction is not as sensitive as urine antigen for the diagnosis of disseminated histoplasmosis

We developed a colorimetric microtiter plate polymerase chain reaction enzyme immunoassay (PCR-EIA) for the detection of Histoplasma capsulatum in urine. The specificity of the PCR assay was confirmed using H. capsulatum (positive control) and Blastomyces dermatitidis (negative control) isolates. The analytical sensitivity of the PCR assay was determined by testing urine samples spiked with freshly grown H. capsulatum organisms and was 2 yeasts per reaction in urine and 0.2 yeasts per reaction in urine sediment after centrifugation. Fifty-one urine specimens positive for H. capsulatum antigen and 25 urine specimens from healthy volunteers were tested blindly. Patient specimens also were cultured for H. capsulatum. The PCR assay was positive in 4 (7.8%) of 51 urine specimens containing antigen and negative in urine specimens from healthy volunteers. The positive PCR results occurred in 4 of 5 urine specimens that were positive by culture, and each exhibited high level of antigenuria (>20 U). Urine cultures were not positive in 24 urine specimens with an antigenuria of 1-19.9 U, but were positive in 5 of 27 urine specimens with antigenuria >20 U. Thus, positive PCR results in urine specimens correlate with positive culture results, but not with antigenuria. The low sensitivity of this PCR assay in urine limits its use in the diagnosis of disseminated histoplasmosis.     

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.     

Diagnostic value of various urine tests in the Jordanian population with urinary tract infection.

We compared the performance of leukocyte esterase and nitrite reductase dipstick tests with microscopic examination and uroculture in cases with clinically suspected urinary tract infection (UTI). We studied urine specimens from 504 Jordanian patients which were obtained by the mid-stream clean catch method and analyzed for bacteria. All samples were subjected to culture. Results of urine dipstick tests and pyuria (white blood cells (WBC)/high power field) were compared with urine culture for each sample. Significant bacteriuria was found in 117 cases (23.2%) with positivity of 59% and 68.5% for the presence of nitrite reductase and leukocyte esterase, respectively. Echerichia coli was the most common organism isolated. The dipstick leukocyte esterase and nitrite testing had a sensitivity of 68.5% and 59% for detecting bacteriuria in UTI cases and specificity of 73.5% and 78%, respectively. The positive predictive value of the tests was 44% and 60%, and the negative predictive value 88.5% and 86.2%, respectively. Microscopic WBC showed 86.5% specificity but low sensitivity. Urine dipstick results and pyuria significantly correlated with the results of urine culture but demonstrated more false-positive results, which ranged from 13.4-26.6%. The probability of growing a urinary pathogen correlated with urinary WBC counts and allowed prediction of the presence or absence of bacteriuria by counting urinary leukocytes. A combination of pyuria and urine dipstick testing appears to be a very useful marker for the diagnosis of UTI. Urine culture can be omitted if both tests are negative.     

Is it meaningful to apply midstream urine culture to urine specimens with negative Gram stain results?

IntroductionGram staining is a convenient method for bacterial estimation. Urine culture is typically used to diagnose urinary tract infections. Therefore, urine culture is also performed on Gram stain-negative urine specimens. However, the frequency of uropathogen identification in these samples remains unclear.MethodsFrom 2016 to 2019, we retrospectively compared the results of Gram staining and urine culture tests on midstream urine specimens submitted for the diagnosis of urinary tract infections to confirm the significance of urine culture on Gram stain-negative specimens. Analysis was performed according to the patients’ sex and age, and the frequency of uropathogen identification in the culture was examined.ResultsA total of 1763 urine specimens (women, 931; men, 832) were collected. Of these, 448 (25.4%) were not positive on Gram staining but were positive on culture. In specimens without bacteria on Gram staining, the frequencies of specimens with uropathogens detected on culture were 20.8% (22/106) in women aged <50 years, 21.4% (71/332) in women aged ≥50 years, 2.0% (2/99) in men aged <50 years, and 7.8% (39/499) in men aged ≥50 years.ConclusionsIn men aged <50 years, the frequency of uropathogenic bacteria identification by urine culture was low in Gram stain-negative specimens. Therefore, urine cultures may be excluded from this group. In contrast, in women, a small number of Gram stain-negative specimens showed significant culture results for the diagnosis of urinary tract infection. Therefore, urine culture should not be omitted in women without careful consideration.     

High incidence of significant urinary ascorbic acid concentrations in a west coast population--implications for routine urinalysis.

Examination of 4379 routine urinalysis specimens with dipsticks sensitive to ascorbic acid showed that 22.8% were positive specimens. The mean urinary vitamin C concentration in this population was 2120 mumol/L. There was a high rate of false-negative dipstick results for hemoglobin in patients with vitamin C in the urine. The highest false-negative rates were observed in urine samples containing less than 50 erythrocytes per high-power field. In further experiments when volunteers consumed supplemental oral USP vitamin C at doses of 100, 250, 500, and 1000 mg or vitamin C-containing fruit juices, even the lowest doses of oral vitamin C or juice resulted in sufficient urinary vitamin C to produce false-negative dipstick results in hemoglobin and glucose testing. To prevent potentially dangerous false-negative results, screening urinalysis protocols relying only on dipstick testing should include a check for urinary vitamin C or use a dipstick that is not subject to vitamin C interference.     

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.     

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...     

Reflect Urine Culture Cancellation in the Emergency Department

Background

The yield of urine culture testing in the emergency department (ED) is often low, resulting in wasted laboratory and ED resources. Use of a reflex culture cancellation protocol, in which urine cultures are canceled when automated urinalysis results predict that culture yield will be low, may help to conserve these resources.

Study Objectives

To identify a reflex culture cancellation protocol consisting of urinalysis-based criteria to limit urine culture over-utilization.

Methods

We studied patients aged 5 years and older whose ED evaluation included both an automated urinalysis and urine culture. Logistic regression models incorporating individual urinalysis components were used to predict culture growth. Receiver operating characteristic curves corresponding to each model were constructed, and the area under the curve was used to identify the model that best predicted positive urine culture growth.

Results

There were 1546 ED patients who met study inclusion criteria. Of these, 314 (20%) had positive urine cultures. Restriction of culture testing to samples with white blood cells > 10 per high-power field, positive nitrites, positive leukocyte esterase, or positive bacteria provided a sensitivity of 96.5% (95% confidence interval [CI] 93.6–98.1%) and specificity of 48.1% (95% CI 45.3–51.0%) for positive urine culture. Implementation of a reflex culture cancellation protocol based on these criteria would have eliminated 604 of 1546 cultures (39%); 11 of 314 positive cultures (3.5%) would have been missed.

Conclusion

These results suggest that a substantial reduction in urine culture testing might be achievable by implementing this protocol. Confirmation of these findings in a validation cohort is necessary.     

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.