Unsatisfactory Performance of Flow Cytometer UF-100 and Urine Strips in Predicting Outcome of Urine Cultures

Zaman, Zahur; Roggeman, Sylvie; Verhaegen, Jan

doi:10.1128/jcm.39.11.4169-4171.2001

Cited by 34 publications

(27 citation statements)

References 8 publications

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“…However, it still had a rather high false-negative rate. The UF-100 was also reported to have a high false-negative rate in the detection of significant bacteriuria (11). In this study, we developed a new flow cytometry-based automated device which was specific for accurate enumeration of bacterial cells in urine and tested the feasibility of the device for detecting significant bacteriuria.…”

Section: Discussionmentioning

confidence: 99%

Enumeration of Bacterial Cell Numbers and Detection of Significant Bacteriuria by Use of a New Flow Cytometry-Based Device

et al. 2006

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A new, automated flow cytometry-based urine bacterium analyzer (UBA) was developed. We assessed the UBA for linearity of measurement, reproducibility of results, carryover rate, and correlation of measured results with those determined by urine culture. We also evaluated its ability to screen urine samples for significant bacteriuria. The UBA showed excellent linearity and a minor carryover rate. Results from the UBA were highly reproducible, and in between-run precision assays, the coefficients of variation for the UBA results were smaller than those for the urine culture results. Two hundred seventy-three urine specimens from patients attending the outpatient clinics of two university-based hospitals were examined. The results for the UBA were compared with those for urine culture. The UBA detected significant bacteriuria with a sensitivity of 96.6%, a specificity of 79.9%, a positive predictive value of 57.0%, a negative predictive value of 98.8%, a false-positive rate of 15.8%, a false-negative rate of 0.7%, and an accuracy of 83.5%. These results were comparable to or better than those obtained with previously reported screening procedures. The UBA can perform accurate enumeration of bacterial cells automatically in 90 seconds and can be used for the screening of significant bacteriuria.Although the standard method for diagnosis of urinary tract infection is quantitative urine culture and identification of bacteria, fewer than 30 percent of urine samples sent to the laboratory are proven positive (6). Thus, a rapid screening method is required to reduce these time-consuming and expensive procedures. We have reported that the flow cytometrybased automatic urinalysis device UF-50 can detect significant bacteriuria with a false-negative rate (FN) of 5.4% (7). For the ideal screening method, the false-negative rate should be lower. For this purpose, we developed a new device to perform enumeration of bacterial cells in urine by using flow cytometry technology equipped with a semiconductor laser. In this paper, we evaluated the linearity and reproducibility of the measurement and compared the measured results with those from the conventional urine culture method using clinical urine specimens. We also evaluated the feasibility of using this new device to predict the results of urine culture. MATERIALS AND METHODSBacterial strains and media. Four bacterial strains, Escherichia coli ATCC 11775, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213, and Enterococcus faecalis ATCC 29212, were purchased from ATCC.Clinical specimens. Urine specimens were collected from patients attending the outpatient clinics of two university hospitals. Patients with urinary diversions or orthotopic neobladder with bowel segments were excluded. Also excluded were the patients who had fistulas between the urinary tract and bowels.A sterile plastic container with a wide opening was used to collect midstream urine. Female patients were asked to wipe their external genitalia with a wet tissue before urinating. Ten millilit...

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Section: Discussionmentioning

confidence: 99%

Enumeration of Bacterial Cell Numbers and Detection of Significant Bacteriuria by Use of a New Flow Cytometry-Based Device

et al. 2006

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“…However, the results of studies that compare the bacterial and leukocyte counts with the UF-100 with urine culture for the diagnosis of UTI vary widely. While some studies have reported an adequate performance in relation to urine culture (6,9,10,13), others have found a relatively large number of false negatives, which decreases sensitivity and makes the UF-100 unsuitable as a screening method to detect negative culture samples (2,15,22). Comparing studies is difficult though, since reported sensitivities and specificities depend on the definition used for gold standard positive and negative urines, and these definitions vary among laboratories.…”

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confidence: 89%

Screening for Urinary Tract Infection with the Sysmex UF-1000i Urine Flow Cytometer

et al. 2011

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The diagnosis of urinary tract infection (UTI) by urine culture is time-consuming and can produce up to 60 to 80% negative results. Fast screening methods that can reduce the necessity for urine cultures will have a large impact on overall turnaround time and laboratory economics. We have evaluated the detection of bacteria and leukocytes by a new urine analyzer, the UF-1000i, to identify negative urine samples that can be excluded from urine culture. In total, 1,577 urine samples were analyzed and compared to urine culture. Urine culture showed growth of >10 3 CFU/ml in 939 samples (60%). Receiver operating characteristics (ROC) curves and ROC decision plots were been prepared at three different gold standard definitions of a negative urine culture: no growth, growth of bacteria at <10 4 CFU/ml, and growth of bacteria at <10 5 CFU/ml. Also, the reduction in urine cultures and the percentage of false negatives were calculated. At the most stringent gold standard definition of no growth, a chosen sensitivity of 95% resulted in a cutoff value of 26 bacteria/l, a specificity of 43% and a reduction in urine cultures of only 20%, of which 14% were false negatives. However, at a gold standard definition of <10 5 CFU/ml and a sensitivity of 95%, the UF-1000i cutoff value was 230 bacteria/l, the specificity was 80%, and the reduction in urine cultures was 52%, of which 0.3% were false negatives. The applicability of the UF-1000i to screen for negative urine samples strongly depends on population characteristics and the definition of a negative urine culture. In our setting, however, the low workload savings and the high percentage of false-negative results do not warrant the UF-1000i to be used as a screening analyzer.

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“…It has already been reported that most FN results are observed primarily in certain patient groups, including those that are immunosuppressed, renal transplant recipients or pregnant woman (2). Of course, it is possible that in some of these cases, microbiologists ''over'' interpret the urine culture and consider them significant.…”

Section: Although the Sysmexmentioning

confidence: 99%

“…᭨ UF-100 detects a large percentage of UTIs, reported sensitivities are only in the range of 70%-90% (1,2,15,18). However, some investigators reported higher sensitivities ()95%), but this caused the specificity to drop to values as low as 15%-49% (11,12).…”

Section: Although the Sysmexmentioning

confidence: 99%

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Use of flow cytometry (Sysmex^® UF-100) to screen for positive urine cultures: in search for the ideal cut-off

Brilha

Proença²,

Melo‐Cristino

et al. 2009

Clinical Chemistry and Laboratory Medicine

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Background: Cultures for urinary tract infections (UTI) constitute a large workload in the clinical microbiology laboratory, although up to 80% are usually negative. Several automated methods are available to screen urines for UTI, one being the flow cytometry-based Sysmex ᭨ UF-100. Methods: The performance of the UF-100 was evaluated over a 16-month period using urine culture as the reference method. Results: During this period, a total of 5356 urine samples were studied (469 children; 3229 women and 1658 men), of which 706 were culture positive (593 grew Gram negative bacilli). Receiver operating characteristics (ROC) curve analysis showed an area under the curve (AUC) of 0.83 for leukocytes and 0.85 for bacterial count. Applying cut-off values reported in the literature gave sensitivities ranging from 75% to 90%, resulting in 73-174 false negatives (FN). Using a logical combination (leukocytes G15=10 6 /L OR bacteria G500=10 6 /L) gave a sensitivity of 98%. However, the specificity dropped to 25%, resulting in 15 FN. Conclusions: Screening urine samples for UTI detects a large number of culture positive samples. However, the rather large number of FN observed precludes the use of the UF-100 as a routine screening method to exclude urine samples from culture. Clin Chem Lab Med 2010;48:289-92.

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Unsatisfactory Performance of Flow Cytometer UF-100 and Urine Strips in Predicting Outcome of Urine Cultures

Cited by 34 publications

References 8 publications

Enumeration of Bacterial Cell Numbers and Detection of Significant Bacteriuria by Use of a New Flow Cytometry-Based Device

Enumeration of Bacterial Cell Numbers and Detection of Significant Bacteriuria by Use of a New Flow Cytometry-Based Device

Screening for Urinary Tract Infection with the Sysmex UF-1000i Urine Flow Cytometer

Use of flow cytometry (Sysmex^® UF-100) to screen for positive urine cultures: in search for the ideal cut-off

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Unsatisfactory Performance of Flow Cytometer UF-100 and Urine Strips in Predicting Outcome of Urine Cultures

Cited by 34 publications

References 8 publications

Enumeration of Bacterial Cell Numbers and Detection of Significant Bacteriuria by Use of a New Flow Cytometry-Based Device

Enumeration of Bacterial Cell Numbers and Detection of Significant Bacteriuria by Use of a New Flow Cytometry-Based Device

Screening for Urinary Tract Infection with the Sysmex UF-1000i Urine Flow Cytometer

Use of flow cytometry (Sysmex® UF-100) to screen for positive urine cultures: in search for the ideal cut-off

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Use of flow cytometry (Sysmex^® UF-100) to screen for positive urine cultures: in search for the ideal cut-off