Glucose Oxidase Test

The glucose oxidase test - which involves the use of commercial, plasticcoated reagent strips (Clinistix, Diastix) or Tes- Tape - is a specific, qualitative test for glycosuria. The test is used primarily to monitor urine glucose in patients with diabetes. Because of this test's simplicity and convenience, patients can perform it at home.

Purpose

• To detect glycosuria
• To monitor urine glucose levels during insulin therapy

Patient preparation

• Explain to the patient that this test determines urine glucose concentration.
• If he's a newly diagnosed patient with diabetes, teach him how to perform a reagent strip test.
• Check his drug history. If he's receiving levodopa, ascorbic acid, phenazopyridine, salicylates, peroxides, or hypochlorites, use Clinitest tablets instead.

Equipment

Specimen container, glucose test strips, reference color blocks

Procedure and posttest care

• Have the patient void; then give him a drink of water.
• Collect a second-voided specimen after 30 to 45 minutes.

Clinistix test

• Dip the test area of the reagent strip in the specimen for 2 seconds.
• Remove excess urine by tapping the strip against a clean surface or the side of the container, and begin timing.
• Hold the strip in the air, and "read" the color exactly 10 seconds after taking the strip out of the urine by comparing it with the reference color blocks on the label of the container.
• Record the results.
• Ignore color changes that develop after 10 seconds.

Diastix test

• Dip the reagent strip in the specimen for 2 seconds.
• Remove excess urine by tapping the strip against the container, and begin timing.
• Hold the strip in the air, and compare the color to the color chart exactly 30 seconds after taking the strip out of the urine.
• Record the results.
• Ignore color changes that develop after 30 seconds.

Tes- Tape

• Withdraw about 1" (3.8 cm) of the reagent tape from the dispenser; dip 1/4 "(0.6 cm) in the specimen for 2 seconds.
• Remove excess urine by tapping the strip against the side of the container, and begin timing.
• Hold the tape in the air, and compare the color of the darkest part of the tape to the color chart exactly 60 seconds after taking the strip out of the urine.
• If the tape indicates 0.5% or higher, wait an additional 60 seconds to make the final color comparison.
• Record the results.

Precautions

• Instruct the patient not to contaminate the urine specimen with toilet tissue or stool.
• Keep the test strip container tightly closed to prevent deterioration of strips by exposure to light or moisture.
• Store it in a cool place (under 86° F [30° C]) to avoid heat degradation.
• Don't use discolored or darkened Clinistix or Diastix or dark yellow or yellow-brown Tes- Tape.

Normal Findings

Normally, no glucose is present in urine.

Abnormal findings

Glycosuria occurs in diabetes mellitus, adrenal and thyroid disorders, hepatic and central nervous system diseases, conditions involving low renal thresh­old (such as Fanconi's syndrome), toxic renal tubular disease, heavy metal poisoning, glomerulonephritis, and nephrosis; in pregnant women; and in those receiving total parenteral nutrition. It also occurs with administration of large amounts of glucose and of certain drugs, such as asparaginase, corticosteroids, carbamazepine, ammonium chloride, thiazide diuretics, dextrothyroxine, large doses of nicotinic acid, lithium carbonate, and prolonged use of phenothiazines.

Interfering factors

• Dilute, stale urine or contamination of the specimen due to toilet tissue, stool, or bacteria
• Use of reagent strips after the expiration date, failure to keep the reagent strip container tightly closed, or failure to record the reagent strip method used
• Presence of reducing substances, such as levodopa, ascorbic acid, phenazopyridine, methyldopa, and salicylates (possible false-negative)
• Tetracyclines (false-negative)