Original ContributionsComparison of test characteristics of urine dipstick and urinalysis at various test cutoff points*,**,*
Introduction
Urinalysis is the most commonly used test for evaluation of emergency department patients with potential urinary tract infections. Unfortunately, in cases in which no other diagnostic studies are needed, urinalysis can significantly increase a patient's time in the ED. Substituting a urine dipstick test for a hospital laboratory urinalysis may be less time-consuming and less expensive, but the dipstick may not be as accurate.
Diagnostic accuracy of urine dipsticks is unclear because methodologies, such as definitions of a positive urine culture and thresholds for test positivity, vary among published studies.1, 2, 3, 4 Blum and Wright1 used only dipstick leukocyte esterase and nitrite as variables in examining diagnostic performance. Bonnardeaux et al3 studied 5 variables: leukocyte esterase, nitrite, protein, glucose, and ketones. Christenson et al2 looked at all 9 variables from the Chemstrip 9 dipstick (Boehringer Mannheim Corporation, Indianapolis, IN). Most studies were conducted in populations that were not typical of ED patients.2, 3, 5 Consequently, some authors recommend confirmatory urinalyses if the urine dipstick results are negative,1, 6 and others if results are positive.2, 3, 6, 7, 8, 9, 10, 11 If the definitions of positive test results, or “test cutoff point,” for urine dipstick and for urinalysis are adjusted, these 2 tests may prove to have comparable sensitivities, specificities, and predictive values at one or more test cutoff points. If this were true, it might be possible to substitute the dipstick test for the urinalysis.
The objective of this study was to compare the test characteristics of urine dipstick and urinalysis at various test cutoff points in women presenting to EDs and an intermediate care center with symptoms of urinary tract infection.
Section snippets
Materials and methods
This was a prospective, observational study of women older than 18 years of age presenting to the Borgess Medical Center ED, Bronson Methodist Hospital ED, or Woodbridge Intermediate Care Center with symptoms suggestive of a urinary tract infection. The study was approved by the institutional review boards of both hospitals.
Inclusion criteria were dysuria, urgency, urinary frequency, urinary incontinence, hematuria, gross pyuria, suprapubic pain or pressure, or flank pain. Patients who were
Results
Three hundred forty-three patients were enrolled. Twelve cases were withdrawn because of missing urinalysis or culture results. The average patient age was 33 years (range, 18 to 84 years). Patients had the following clinical findings: 84% (278/331) had urgency; 84% (278/331), frequency; 79% (261/331), dysuria; 39% (129/331), suprapubic tenderness; 18% (60/331), costovertebral angle tenderness. Four percent (13/331) reported pregnancy. Two percent (7/331) had been catheterized within 2 weeks
Discussion
Urinary tract infection is a problem that is commonly treated in EDs and urgent care centers. This study demonstrates that bedside urine dipsticks can be substituted for urinalysis to diagnose uncomplicated urinary tract infections. Use of dipsticks instead of urinalysis will decrease patient time in the ED and the cost of testing. However, basing treatment decisions on either urine dipsticks or urinalysis alone results in substantial undertreatment and overtreatment rates at most test cutoff
Acknowledgements
Author contributions: RLL designed the study and obtained research funding. RLL, SG, DK, WS, and GS participated in recruitment of participating centers, data collection, and quality control activities. RLL analyzed the data and wrote the manuscript; SG and DK contributed to manuscript revisions. All authors gave final approval of the version to be published. RLL takes responsibility for the paper as a whole.
We gratefully acknowledge Diana Cucos for her assistance with the statistical analysis
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Author contributions are provided at the end of this article.
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Supported by grant No. 016-PIRAP/96 from the Blue Cross/Blue Shield of Michigan Foundation.
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Address for reprints: Richard L. Lammers, MD, Department of Emergency Medicine, Michigan State University/Kalamazoo Center for Medical Studies, 1000 Oakland Drive, Kalamazoo, MI 49008;,616-337-6600, fax 616-337-6475;,E-mail [email protected].