Urinary Tract Infection - Diagnosis

Clean-Catch Sample. A clean-catch sample for UTI depends on a sample free of contaminants normally present at the opening of the urethra (e.g., white blood cells and bacteria unrelated to UTIs). To obtain an untainted urine sample, doctors usually request a so-called midstream, or clean-catch, urine sample. To provide this, the following steps are taken:

Patients must first wash their hands thoroughly, then wash the penis or vulva and surrounding area four times, with front-to-back strokes, using a new soapy sponge each time.
The patient must then begin urinating into the toilet and stop after a few drops.
The patient then positions the container to catch the middle portion of the stream. Ideally, this urine will contain only the bacteria and other evidence of the urinary tract infection.
The patient then urinates the remainder into the toilet.
The patient securely screws the container cap in place without touching the inside of the rim.

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The sample is generally given to the doctor or sent to the laboratory for analysis. For the majority of cases of suspected cystitis, this sample is considered adequate. In fact, a 2000 study reported that the clean-catch sample had identical contamination rates as a simple urine sample taken with no precautions. Researchers in the study suggested that in young, sexually active women with symptoms of cystitis, a urine sample may not even be necessary.

Incontinence Pads. Testing and diagnosing UTIs in elderly patients who are incontinent is especially difficult, because of the similarities in symptoms. Researchers have found that pressing a dipstick into an incontinence pad is an effective way to screen for urinary tract infections in incontinent patients.

Collection with a Catheter. Some patients (e.g., small children, elderly people, or hospitalized patients) cannot provide a urine sample. In such cases, a catheter may be inserted into the bladder to collect urine. This is the best method for providing a contaminant-free sample.

Urinalysis

A urinalysis involves a physical and chemical examination of urine. In addition, the urine is spun in a centrifuge to allow sediments containing blood cells, bacteria, and other particles to collect. This sediment is then examined under a microscope. A urinalysis, then, offers a number of valuable clues for an accurate diagnosis:

Simply observing the urine for color and cloudiness can be important.
Acidity is measured.
White blood cells (leukocytes) are counted. A high count in the urine is referred to as pyuria. (A leukocyte count over 10 per microliter is considered to indicate pyuria.) This is very accurate in identifying the disease when it's present, but it also tests positive in many people who do not have a UTI. Pyuria is usually sufficient for a diagnosis of UTI in nonhospitalized patients if other standard symptoms (or just fever in small children) are also present.