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

Abstract

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.

Analytical and Clinical Evaluation of Sysmex Uf1000i for Automated Screening of Cerebrospinal Fluids Analitička I Klinička Evaluacija Uređaja Sysmex Uf1000i Za Automatski Skrining Cerebrospinalnih Tečnosti

“…The good performance for bacterial load assessment is another important and innovative finding of this study, wherein the UF-1000i displayed an AUC of 0.99, a sensitivity of 1.00 and a specificity of 0.97 at a threshold of 19 bacteria/mL. It is thus likely that the UF-1000i may be reliably used for the routine screening of bacterial load in CSFs, as already suggested for the screening of urinary tract infections (22,23).…”

Automated urinalysis: First experiences and comparison of automated urinalysis system and manual microscopy

“…[9][10][11] Conventional microscopic analysis of urine sediments although considered to be the reference method, in values several methodological steps such a centrifugation and discarding that lead to loss and destruction of cells and result in imprecision and inaccuracy. 6 These procedures are not required in the automated analysis.…”

Selective detection of bacteria in urine with a long-range surface plasmon waveguide biosensor

“…In addition, dipsticks have poor sensitivity especially with diluted urine or low colony count samples. In the labeled biosensing category, flow cytometry is a family of automated systems providing results in less than one minute for detection levels below 10 5 CFU/ml [3][4][5]. Selectivity in flow cytometry can be obtained by double staining with fluorescent dyes [6].…”