Waived Tests and Glucose Tolerance Test

Waived Tests

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Waived tests are the laboratory procedures that are the simplest to perform but provide important diagnostic information. They can be performed accurately by non laboratory health care workers with minimum training. These procedures have traditionally been performed in physicians’ offices and clinical laboratories for years, but have since found their way into such settings as long-term care facilities, at bedside in acute care settings, ambulatory settings, insurance companies, and home health care. Waived tests have become a valuable component of the competency menu in multi skilling for the non laboratory health care provider, as the industry and its members prepare for the evolution of health care roles in the 21st century. These procedures are regulated by a variety of health care agencies.

Moderately complex tests require more highly trained personnel, a procedure manual, instrument calibration, specific quality control procedures, proficiency testing, and extensive documentation and record keeping.

Glucose Tolerance Test

Glucose is the sugar the body uses for energy. Patients with untreated diabetes have high blood glucose levels. Glucose tolerance tests are one of the tools used to diagnose diabetes. Determine how quickly it is cleared from the blood. The test is usually used to test for diabetes, insulin resistance, and sometimes reactive hypoglycemia and acromegaly, or rarer disorders of carbohydrate metabolism.

With type 2 diabetes, the illness and symptoms tend to develop gradually (over weeks or months). This is because in type 2 diabetes you still make insulin (unlike type 1 diabetes). However, you develop diabetes because: you do not make enough insulin for your body's needs, or the cells in your body do not use insulin properly. This is called 'insulin resistance'. The cells in your body become resistant to normal levels of insulin. This means that you need more insulin than you normally make to keep the blood glucose level down; or a combination of the above two reasons.

Above-normal blood glucose levels can be used to diagnose type 2 diabetes or high blood glucose during pregnancy (gestational diabetes). Insulin levels may also be measured. (Insulin is the hormone produced by the pancreas that moves glucose from the blood into cells.)

The oral glucose tolerance test is used to screen pregnant women for gestational diabetes between 24 and 28 weeks of pregnancy. It may also be used when the disease is suspected, even though the fasting blood glucose level is normal.

Interpretation

Normal blood values for a 75-gram oral glucose tolerance test used to check for type 2 diabetes in those who are not pregnant:

Fasting: 60 -100 mg/dL

1 hour: less than 200 mg/dL

2 hours: less than 140 mg/dL

Higher-than-normal levels of glucose may mean you have prediabetes, diabetes, or gestational diabetes. Between 140 - 200 mg/dL is called impaired glucose tolerance. Your doctor may call this "prediabetes." It means you are at increased risk for developing diabetes. A glucose level of 200 mg/dL or higher is a sign of diabetes. However, high glucose levels may be related to another medical problem (for example, Cushing syndrome).

Procedure

Ÿ  The test takes up to 3 hours.

Ÿ  Eat normally for several days before the test.

Ÿ  Do not eat or drink anything for at least 8 hours before the test. You cannot eat during the test. In preparation for the oral glucose tolerance test, the person should eat and drink as they normally would. The morning of the test, the person should not smoke or consume caffeine.

Ÿ  Ask your health care provider if any of the medicines you take can affect the test results.

Ÿ  Before the test begins, a sample of blood will be taken.

Ÿ  You will then be asked to drink a liquid containing a certain amount of glucose (usually 75 grams). 1.75 grams of glucose per kilogram of body weight, to a maximum dose of 75g. Dose should be drunk within 5 minutes. Your blood will be taken again every 30 to 60 minutes after you drink the solution.

Ÿ  If renal glycosuria (sugar excreted in the urine despite normal levels in the blood) is suspected, urine samples may also be collected for testing along with the fasting and 2 hour blood tests.

Factors that may affect the test results

Ÿ  Acute stress (for example, from surgery or an infection)

Ÿ  Vigorous exercise

Ÿ  Several drugs may cause glucose intolerance, including:

Ÿ  Atypical antipsychotic medications, including aripiprazole, olanzapine, quetiapine, risperidone, and ziprasidone

Ÿ  Beta-blockers (for example, propranolol)

Ÿ  Birth control pills

Ÿ  Corticosteroids (for example, prednisone)

Ÿ  Dextrose

Ÿ  Epinephrine

Ÿ  Estrogens

Ÿ  Glucagon

Ÿ  Isoniazid

Ÿ  Lithium

Ÿ  Phenothiazines

Ÿ  Phenytoin

Ÿ  Salicylates (including aspirin)

Ÿ  Thiazide diuretics (for example, hydrochlorothiazide)

Ÿ  Triamterene

Ÿ  Tricyclic antidepressants

Ÿ  Medicines that could affect the blood glucose.