Tecnólogo Médico

Infect Dis Obstet Gynecol 2001;9:249–255

Urinalysis and urinary tract infection: update for clinicians
Jennifer L. Young and David E. Soper
Medical University of South Carolina, Charleston, SC
Dysuria is a common presenting complaint of women and urinalysis is a valuable tool in the initial evaluation of this presentation. Clinicians need to be aware that pyuria is the best determinate ofbacteriuria requiring therapy and that values significant for infection differ depending on the method of analysis. A hemocytometer yields a value of 10 WBC/mm 3 significant for bacteriuria, while manual microscopy studies show 8 WBC/high-power field reliably predicts a positive urine culture. In cases of uncomplicated symptomatic urinary tract infection, a positive value for nitrites and leukocyteesterase by urine dipstick can be treated without the need for a urine culture. Automated urinalysis used widely in large volume laboratories provides more sensitive detection of leukocytes and bacteria in the urine. With automated microscopy, a value of > 2 WBC/hpf is significant pyuria indicative of inflammation of the urinary tract. In complicated cases such as pregnancy, recurrent infectionor renal involvement, further evaluation is necessary including manual microscopy and urine culture with sensitivities. Key words: DYSURIA; PYURIA; BACTERIURIA; URINE CULTURE; AUTOMATED URINALYSIS

As many as one in four women experience an episode of dysuria each year, making this one of the most common presenting complaints of women seen by clinicians1. Dysuria suggests the diagnosis ofcystitis but may be present in other conditions such as vaginitis, chlamydial urethritis or pyelonephritis2. Urinalysis is valued as a quick and inexpensive screening method for the presence of a lower urinary tract infection (UTI). Often this test is used in conjunction with or in place of a urine culture in the diagnosis of a UTI. However, a recent study found many practicing clinicians use differentstandards to determine the presence or absence of a UTI, most not updated on current literature3. To further complicate matters, the level of automation in urinalysis is increasing and accepted cut-off values differ for these more sensitive methods. This article will review the components of a standard urinalysis, examine the usefulness of each in the diagnosis of UTI, and

bring the clinician upto date on automated urinalysis procedures.

BACTERIURIA IN DIAGNOSIS
While a urine culture is the gold standard in the diagnosis of a UTI, the limitations of this test have led many physicians to use urinalysis as an initial step in the evaluation of dysuria. Bacteriuria is classically defined as a urine culture with greater than 100 000 cfu/ml of a single microorganism4. This valuedistinguishes patients with asymptomatic bacteriuria from those with a contaminated specimen. However, Stamm and colleagues5 found that this culture count was insufficient to include almost half of patients with symptoms of dysuria and frequency. In a study of 181 women with symptoms of dysuria and frequency, 102 had 105 cfu/ml but 79 had < 105 cfu/ml and would not have yielded a positive culture by thestandard

Correspondence to: David E. Soper, MD, Medical University of South Carolina, Gynecology & Obstetrics, 96 Jonathan Lucas St. Suite 634, P.O. Box 250619, Charleston, SC 29425, USA. Email: soperde@musc.edu

Review article

249

Urinalysis and UTI

Young and Soper

criterion. Further study demonstrated that women with dysuria, pyuria and a colony count of 103 cfu/ml have a lowerUTI1,5. The additional problem of urine sample contamination clouds the already muddy picture surrounding urine culture. Several studies found 29–32% of urine cultures were contaminated and concluded that the methodology used in collection does not alter this value6,7. Because of these difficulties with urine culture, in addition to the fact that it is slow and expensive, physicians have turned...