Ann Clin Microbiol.  2018 Dec;21(4):75-79. 10.5145/ACM.2018.21.4.75.

Selection of Unnecessary Urine Culture Specimens Using Sysmex UF-5000 Urine Flow Cytometer

• Song D
• Lee HJ
• Jo SY
• Lee SM
• Chang CL

• KMID: 2429650
• DOI: http://doi.org/10.5145/ACM.2018.21.4.75

Abstract

BACKGROUND
Urine culture is one of the most frequently requested tests in microbiology. Automated urine analyzers yield much infection-related information. The Sysmex UF-5000 analyzer (Sysmex, Japan) is a new flow cytometry urine analyzer capable of quantifying urinary particles, including bacteria, WBCs, and yeast-like cells (YLCs) and can provide a Gram stainability flag. In this work, we evaluated how many unnecessary urine cultures could be screened out using the UF-5000.
METHODS
We compared the culture results of 126 urine samples among 453 requested urine cultures (from sources other than the Urology and Nephrology departments) with urinalysis results. Urine cultures were considered positive if bacterial or YLC growth was ≥104 CFUs/mL.
RESULTS
We used urinalysis cut-off values of 50/µL and 100/µL for bacteria and YLC, respectively. Forty eight of the 126 (38.1%, or 10.6% of 453 requested) cultures were below these cut-off values and did not contain any culture-positive samples.
CONCLUSION
Bacteria and YLC counts generated using the UF-5000 analyzer could be used to screen out negative cultures and reduce urine culture volume by ~10% without sacrificing detection of positive cultures.

Keyword

Sysmex UF-5000 flow cytometer; Unnecessary urine cultures; Urinary tract infection

MeSH Terms

Bacteria
Flow Cytometry
Nephrology
Urinalysis
Urinary Tract Infections
Urology

Figure

• 

  Fig. 1 Classification of culture negative urine samples using the three urinalysis parameters. 1) LE (N), negative (−) or trace (+/−) leukocyte esterase by urine reagent strip analysis; 2) nitrite (N), negative (−) nitrite by urine reagent strip analysis; and 3) Flag (N), no or unclassified flag by UF-5000 analysis. Abbreviations: LE, leukocyte esterase; N, negative.

• 

  Fig. 2 Distribution of WBC, bacteria and YLC counts according to culture results. The UF-5000 analyzer produced a result of 105 for bacterial counts >105. A bacterial count of 0 is expressed as 1.0 and a YLC count of 0 as 0.1 (these values were minimum values in bacterial and YLC count data set, respectively) because the X-axis was transformed to a log scale. Abbreviations: YLC, yeast-like cell; WBC, white blood cell.

• 

  Fig. 3 Receiver operating characteristic (ROC) curves of WBC, bacteria and YLC counts versus urine culture results. The red marks in left and center graphs indicate the cut-off values for bacteria (50/µL) and YLCs (100/µL), respectively. Abbreviations: YLC, yeast-like cell; WBC, white blood cell.

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