Use of Automated Urine Microscopy Analysis in Clinical Diagnosis of Urinary Tract Infection: Defining an Optimal Diagnostic Score in an Academic Medical Center Population

Abstract

A retrospective case record study was conducted that established a scoring tool based on clinical and iQ200 parameters, able to predict or rule out the clinical diagnosis of UTI in the majority of adult patients in an academic hospital. Automated standardized quantitative urine analysis, such as iQ200 analysis, is on the rise because of its high accuracy and efficiency compared to those of traditional urine analysis. Previous research on automated urinalysis focused mainly on predicting culture results but not on the clinical diagnosis of urinary tract infection (UTI). A retrospective analysis was conducted of consecutive urine samples sent in for culture because of suspected UTI. UTI was defined by expert opinion, based on reported symptoms, conventional urine sediment analysis, and urine cultures. Parameters of iQ200 analysis and clinical symptoms and signs were compared between cases and controls. Optimal cutoff values were determined for iQ200 parameters, and multivariate logistic regression analysis was used to identify the set of variables that best predicts the clinical diagnosis of UTI for development of a scoring tool. A total of 382 patients were included. Optimal cutoff values of iQ200 analysis were 74 white blood cells (WBC)/μl, 6,250 "all small particles" (ASP)/μl, and a bacterial score of 2 on an ordinal scale of 0 to 5. The scoring tool attributed 1 point for frequent micturition or increased urge, 2 points for dysuria, 1 point for a bacterial score of ≥2, 2 points for WBC/μl of ≥50, and an additional point for WBC/μl of ≥150. This score had a sensitivity of 86% and a specificity of 92% when using a threshold of <4 points. The combination of iQ200 analysis and a simple survey could predict or rule out UTIs in a majority of patients in an academic medical center.

Prediction of urine culture results by automated urinalysis with digital flow morphology analysis

“…Another study with the iQ200 system exhibited an acceptable NPV of 97.7% and approximately 50% reduction of urine culture when using WBC ≥ 4/HPF as a cutoff in predicting urine culture results, but the PPV was only 24.5% in the same study 17 . The scoring system suggested by Foudraine et al, which was composed of clinical symptoms including dysuria and urgency and the number of WBCs obtained by the iQ200 analyzer, gave good diagnostic performance with a high AUC value of 0.950 for predicting positive blood cultures 18 . However, the diagnostic performance of a test could vary according to the characteristics and composition of cases and controls included in each study, thus it would be difficult to directly compare diagnostic performance among the studies.…”

Automated urinalysis combining physicochemical analysis, on-board centrifugation, and digital imaging in one system: A multicenter performance evaluation of the cobas 6500 urine work area

“…This feature may be of particular relevance in academic centers and teaching hospitals, where higher proportions of complex urine samples with abnormal particles may be encountered compared with non-academic centers. Rapid response times for urinalysis are also essential for efficient collaboration with microbiology departments in order to guide decisions on patient management; up to 60% of urine cultures can be avoided with early recognition (within 10–15 min) of a negative urine screen in patients with suspected UTI [72]. Finally, there was good agreement for the quantitative determination of sample WBC content between the cobas u 701 module, iQ200 system and KOVA visual microcopy.…”

Deconstructing the urinalysis: A novel approach to diagnostic and antimicrobial stewardship

“…12 The microscopic examination can also provide information on the presence of microorganisms in the urine but the clinical value has not been systematically studied and likely varies between populations. 27 Most are performed by automated flow cytometry or image analysis with or without manual microscopic confirmation and cannot distinguish pathogens from nonpathogens or viable from nonviable organisms. Hence, detection of bacteria on the microscopic examination may be associated with positive urine cultures, but it cannot differentiate between asymptomatic bacteriuria, contamination, and UTI.…”

“…Currently, some hospitals limit the use of microscopy in patients that meet specific criteria on urinalysis, while other laboratories limit urine cultures to patients that meet specific urinalysis criteria. 27,48 Laboratories can consider changing the ordering or reporting of urinalysis parameters to reflect underlying disease states based on the clinician's evaluation: inflammation, metabolic disorders, renal disorders, etc (Table 1). Our suggested panels may serve as a starting point for streamlined evaluation of urine.…”