The development and validation of different decision-making tools to predict urine culture growth out of urine flow cytometry parameter

Mûller, Martín; Seidenberg, Ruth; Schuh, Sabine K.; Exadaktylos, Aristomenis K.; Schechter, Clyde B.; Leichtle, Alexander Benedikt; Hautz, Wolf E.

doi:10.1371/journal.pone.0193255

Cited by 13 publications

(33 citation statements)

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“…Unfortunately, however, our results did not support this hypothesis. None of the UFC parameters, alone or in combination with bacterial count, were able to predict mixed culture, in accordance with other reports [5,9]. Thus, these samples still need to be cultured, since in many cases they have bacterial counts above the diagnostic cut-off.…”

Section: Discussionsupporting

confidence: 89%

“…This could benefit both the patient and healthcare system, as it allows for a more rapid clarification of the patient's condition, possibly reducing the number of hospital bed-days per patient, as well as the use of antibiotics. Flow cytometry is reported to be a rapid, accurate and robust screening method that can substantially reduce the number of excessive cultivations in the microbiology laboratory [4][5][6][7][8][9]. However, if the instrument cut-off regarding bacterial counts is set low, according to defined thresholds for positive urine cultures [2,10], there is a risk that the count measured by the flow cytometer represents carryover from a previous, rather than the current sample if rinsing of the instrument between samples is insufficient.…”

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confidence: 99%

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Use of Sysmex UF-5000 flow cytometry in rapid diagnosis of urinary tract infection and the importance of validating carryover rates against bacterial count cut-off

Haugum

Haugan

Skage

et al. 2021

Journal of Medical Microbiology

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Introduction. Urinary tract infections are common bacterial infections worldwide. Urine culture is the gold standard method to identify and quantify the presence or absence of bacteria in urine. Flow cytometry, which can differentiate and quantify multiple particles (including bacteria) in the urine, presents an alternative method for rapid screening to rule out bacteriuria. Hypothesis. Adding flow cytometry to identify urine samples without bacteriuria could substantially reduce the number of urine samples that need to be cultured as well as the response time for negative results. However, the level of instrument rinsing between samples could affect sample-to-sample carryover rate, a concept given little attention in previous studies. Aim. We aimed to evaluate urine flow cytometry as a rapid screening method to identify urine samples without significant bacterial growth, including analyses of cross-contamination and sample-to-sample carryover rate. Methodology. We analysed 3919 urine samples by quantitative urine culture and flow cytometry screening (Sysmex UF-5000). Receiver operator characteristic (ROC) curve analyses were used to test method agreement to identify: (a) positive vs. negative culture and (b) mixed vs. pure culture. In addition, we performed carryover and cross-contamination studies. Results. ROC curve analyses identified bacterial count (BACT ml−1) and leucocyte count (WBC µl−1) as possible predictors of bacterial growth in the total material and subpopulations, except pregnant women (n=451). This subgroup was excluded from further analyses, leaving a final 3468 urine samples. Area under the ROC curve was 0.94 (95 % CI 0.93–0.95) and 0.81 (95 % CI 0.79–0.82) for bacterial and leucocyte count, respectively. A bacterial count cut-off of 30 BACT ml−1 resulted in 95.2 % sensitivity and 91.2 % negative predictive value, resulting in approximately 30 % of urine samples that could be reported as negative without culture. Use of high-level rinse modes was necessary to ensure carryover rates <0.05 %. Conclusion. Flow cytometry is a suitable and rapid method to rule out urine samples without significant bacterial growth. Rinses between samples should be adjusted, depending on the cut-off used, to prevent sample-to-sample carryover, whereas cross-contamination can be eliminated by the use of separate urine aliquots for flow cytometry analysis and urine culturing respectively.

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Section: Discussionsupporting

confidence: 89%

mentioning

confidence: 99%

Use of Sysmex UF-5000 flow cytometry in rapid diagnosis of urinary tract infection and the importance of validating carryover rates against bacterial count cut-off

Haugum

Haugan

Skage

et al. 2021

Journal of Medical Microbiology

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“…This is a secondary analysis of a published data set, in which we developed generic tools to predict significant bacterial growth in urine culture from UFC measurements [ 14 ]. In the study presented here, we focus on patient characteristics: (i) age (>65 years and ≤65 years); (ii) gender; (iii) fever (>38.0°C on presentation in accordance with a previous UFC study [ 15 ]); (iv) urinary symptoms such as dysuria, urinary frequency, and UTI-specific abdominal pain, including suprapubic pain, lower abdominal pain, or flank pain; (v) renal insufficiency (classified by the medical history); (vi) diabetic patients; and (vii) immunosuppressed patients.…”

Section: Methodsmentioning

confidence: 99%

“…The UFC is fully automated, and results can be viewed online by the attending physician 30 min after the start of the analysis. The procedures for urine collection, storage, and analysis are described in a previous publication [ 14 ].…”

Section: Methodsmentioning

confidence: 99%

“…To rule out negative urine culture (nonsignificant bacterial growth), most studies have focused on fixed cut-offs determined by UFC for counts of leucocytes and bacteria in the urine (UFC leucocytes and UFC bacteria, respectively) that help to decide whether culturing is rational and indicated for treatment [ 11 – 13 ]. Several diagnostic algorithms suggest an “optimal” cut-off for predicting significant bacterial growth in urine culture [ 14 ]. Thus, the diagnosis of a UTI remains challenging, as the individual medical history and comorbidities of the patient might influence the diagnostic validity of fixed UFC cut-offs for predicting significant bacterial growth in urine culture.…”

Section: Introductionmentioning

confidence: 99%

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Diagnosis of Urinary Tract Infections by Urine Flow Cytometry: Adjusted Cut-Off Values in Different Clinical Presentations

et al. 2019

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Background. Bacterium and leucocyte counts in urine can be measured by urine flow cytometry (UFC). They are used to predict significant bacterial growth in urine culture and to diagnose infections of the urinary tract. However, little information is available on appropriate UFC cut-off values for bacterium and leucocyte counts in specific clinical presentations. Objective. To develop, validate, and evaluate adapted cut-off values that result in a high negative predictive value for significant bacterial growth in urine culture in common clinical presentation subgroups. Methods. This is a single center, retrospective, observational study with data from patients of the emergency department of Bern University Hospital, Switzerland, with suspected infections of the urinary tract. The patients presented with different symptoms, and urine culture and urine flow cytometry were performed. For different clinical presentations, the patients were grouped by (i) age (>65 years), (ii) sex, (iii) clinical symptoms (e.g., fever or dysuria), and (iv) comorbidities such as diabetes and immunosuppression. For each group, cut-off values were developed, validated, and analyzed using different strategies, i.e., linear discriminant analysis (LDA) and Youden’s index, and were compared with known cut-offs and cut-offs optimized for sensitivity. Results. 613 patients were included in the study. Significant bacterial growth in urine culture depended on clinical presentation and ranged from 32.3% in male patients to 61.5% in patients with urinary frequency. In all clinical presentations, the predictive accuracy of UFC leucocyte and UFC bacterium counts was good for significant bacterial growth in urine culture (AUC≥0.88). The adapted LDA95 equations did not exhibit consistently high sensitivity. However, the in-house cut-offs (test positive if UFC leucocytes>17/μL or UFC bacteria>125/μL) were highly sensitive (>90%). In female, younger, and dysuric patients, even higher cut-offs for UFC leucocytes (169/μL, 169/μL, and 205/μL) exhibited high sensitivity. Specificity was insufficient (<0.9) for all tested cut-offs. Conclusions. For various clinical presentations, significant bacterial growth in urine culture can be excluded if flow cytometry measurements give a bacterial count of ≤125/μL or a leucocyte count of ≤17/μL. In female patients, dysuric patients, and patients younger than ≤65 years, the leucocyte cut-off can be increased to 170/μL.

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Flow Cytometry Methods to Monitor Immune Dysregulation Associated with Spaceflight

Crucian¹,

Makedonas²,

Sams³

2019

Stress Challenges and Immunity in Space

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The development and validation of different decision-making tools to predict urine culture growth out of urine flow cytometry parameter

Cited by 13 publications

References 32 publications

Use of Sysmex UF-5000 flow cytometry in rapid diagnosis of urinary tract infection and the importance of validating carryover rates against bacterial count cut-off

Use of Sysmex UF-5000 flow cytometry in rapid diagnosis of urinary tract infection and the importance of validating carryover rates against bacterial count cut-off

Diagnosis of Urinary Tract Infections by Urine Flow Cytometry: Adjusted Cut-Off Values in Different Clinical Presentations

Flow Cytometry Methods to Monitor Immune Dysregulation Associated with Spaceflight

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