Urinalysis

The urinalysis department, often paired with the chemistry or hematology department, is where urine is visually, chemically, and microscopically examined. Urine specimens are received in sterile cups or urinalysis tubes.

The first step in urinalysis is the visual inspection of the urine specimen. The urine is examined for color and clarity. Normal, healthy urine varies from pale yellow (dilute) to amber (concentrated). Normal urine is clear at first and then becomes cloudy when allowed to sit. If the specimen is cloudy or turbid before it sits, the lack of clarity may indicate infection. Unusual odors may also indicate infection.

The second step in urinalysis is chemical examination. Chemical examination is performed by using a urine test strip known as the dipstick or instrumentation. The dipstick contains up to 10 pads, each containing a specific chemical marker for various analytes, including leukocytes, nitrites, urobilinogen, protein, pH, hemoglobin, specific gravity, ketones, bilirubin, and glucose. When the strip is dipped in the urine, the pads turn different colors. The colors are compared against a color scale on the bottle that indicates their quantitative values based on the lightness, darkness, and hue of the colors. This is performed by either a semi-automated analyzer or a trained professional.

The third step in urinalysis is the microscopic evaluation. If an abnormality is detected in visual and/or chemical examination, the urine will be microscopically reviewed for formed elements, such as cells, casts, and crystals. For example, if leukocytes and nitrites are positive on the dipstick, the specimen will undergo microscopic examination for the presence of bacteria and leukocytes.