Simple screening tests that determine blood and urine glucose levels are used to aid in the diagnosis of diabetes mellitus.
a. Fasting Blood Sugar. The fasting blood sugar (FBS) test measures the amount of sugar present in the blood after a patient has been fasting for a prescribed amount of time (generally 6-8 hours). An elevated fasting blood sugar level indicates the possibility of diabetes and the need for further investigation.
b. Two-Hour Post-Prandial Blood Sugar. The two-hour post-prandial blood sugar (two percent ppBS) is a common diagnostic test to determine how well sugar is metabolized by the body. A patient remains fasting for 6-8 hours, a fasting blood specimen is drawn, and the patient is given a high carbohydrate meal. The meal contains a measured amount of carbohydrates. The patient must eat the entire meal within 15 minutes. Two hours after completion of the meal, another blood sugar level is drawn. In a person with normal metabolism, the blood sugar level has returned to normal range within two hours after the meal. An elevated blood sugar level indicates the possibility of diabetes and the need for further investigation.
c. Glucose Tolerance Test. The glucose tolerance test (GTT) test is performed when a patient is found to have an elevated blood sugar level or sugar in the urine. This test is used to evaluate the body’s use of glucose. During this test, blood and urine specimens are collected at timed intervals following the ingestion of a measured amount of glucose. The test normally proceeds in this manner:
(1) The patient may be required to follow a prescribed high carbohydrate diet for three days prior to the test date.
(2) The patient must fast for the required period of time prior to the start of the test, normally 6-12 hours.
(3) Blood and urine are collected while the patient is fasting.
(4) The patient is given a measured amount of glucose solution to drink, which must be consumed quickly.
(5) Blood and urine are collected at timed intervals after the ingestion of the glucose drink. Intervals are normally at 1/2 hour, 1 hour, 2 hours, and even up to 6 hours following the ingestion of the glucose drink.
(6) The patient is permitted to take water only during the duration of the test. This is done to make the patient more comfortable and to facilitate voiding for the urine specimen collection.
d. Urinalysis. Urine tests are used to detect the presence of glucose or acetone in the urine. Normally, urine contains no sugar or acetone. When excess sugar accumulates in the blood, it “spills over” into the urine during filtration of the blood by the kidneys. Urine must be tested for sugar and acetone on a regular schedule. This is normally done IAW ward SOP or the physician’s orders. Common times are prior to each meal and at bedtime.
(1) Urine. Always use freshly voided urine for testing. Stale urine will not provide accurate results. Do not use urine that has been standing in a urinary drainage bag.
(2) Double Void. For complete accuracy, the “double void” method should be used when testing urine. Instruct the patient to empty his bladder, wait 15-30 minutes, and void again. Test the urine from the second voiding.
(3) Clinitest tablets. Place 10 drops of water into a test tube. Add 5 drops of fresh urine. Drop in one of the clinitest tablets. Wait 15 seconds and compare the color of the solution in the test tube to the appropriate color chart (enclosed in the kit) to determine the concentration of sugar present.
(a) This chemical reaction is heat producing. Always use a test tube rack to hold the tube. Never hold it in your hand.
(b) Document the test results in the patient’s record.
(4) Acetest tablets. Place one drop of fresh urine onto an acetest tablet. If the tablet turns purple, the test is positive for the presence of acetone. Document the test results in the patient’s record.
(5) Ketodiastix. Test strips measure glucose and acetone at the same time. Dip one ketodiastix quickly in the fresh urine. Time the readings according to the instructions provided and use the color chart on the ketodiastix bottle to determine the presence of acetone and the concentration of glucose. Document the results in the patient’s record.