Type of test

Blood

 Normal findings

 2-Hour PPG

 0-50 years: < 140 mg/dL or < 7.8 mmol/L (SI units)

50-60 years: < 150 mg/dL

60 years and older: < 160 mg/dL

1-Hour glucose screen for gestational diabetes < 140 mg/dL

Test explanation and related physiology

For this study, a meal acts as a glucose challenge to the body’s metabolism. Normally, insulin is secreted immediately after a meal in response to the elevated blood glucose level, causing the level to return to the premeal range within 2 hours. In patients with diabetes, the glucose level usually is still elevated 2 hours after the meal. The PPG is an easily performed screening test for diabetes mellitus. If the results are greater than 140 mg/dL and less than 200 mg/dL, a glucose tolerance test (GTT, p. 469) may be performed to confirm the diagnosis. If the 2-hour PPG is greater than 200 mg/dL, a diagnosis of diabetes mellitus is confirmed.

The 1-hour glucose screen is used to detect gestational diabetes mellitus (GDM). Screening for GDM is performed with a 50- to 100-g oral glucose load followed by a glucose level determination 1 hour later. This is called the O’Sullivan test. Screening is done between weeks 24 and 28 of gestation. However, patients with risk factors such as a previous history of GDM may benefit from earlier screening. Patients whose serum glucose levels equal or exceed 140 mg/dL may be evaluated by a 3-hour glucose tolerance test. A 100-g oral glucose load is indicated for the diagnosis of gestational diabetes when results of the 50-g oral glucose load 1-hour screening test result are abnormal.

Interfering factors

• Stress can increase glucose levels.

 • If the patient is not able to eat the entire test meal or vomits some or all of the meal, levels will be falsely decreased.

Procedure and patient care

• See inside front cover for Routine Blood Testing.

 • Fasting: yes • Blood tube commonly used: red or gray

* For the 2-hour PPG, instruct the patient to eat the entire meal (with at least 75 g of carbohydrates) and then not to eat anything else until the blood is drawn.

 • For the 1-hour glucose screen for GDM, give the fasting or non-fasting patient a 50-g oral glucose load.

* Instruct the patient not to smoke during the testing. Smoking may increase glucose levels.

* Inform the patient that he or she should rest during the 1- or 2-hour interval.

 Abnormal findings

Increased levels

- Diabetes mellitus

 -Gestational diabetes mellitus

 -Malnutrition

 -Hyperthyroidism

 -Acute stress response

 -Cushing syndrome

 -Pheochromocytoma

 -Chronic renal failure

 -Glucagonoma

 -Diuretic therapy

-Corticosteroid therapy

 -Acromegaly

-Extensive liver disease

Decreased levels

- Insulinoma

 -Hypothyroidism

 -Hypopituitarism

 -Addison disease

 -Insulin overdose

 -Malabsorption or maldigestion

مواضيع ذات صلة

Immunoglobulins

Complement

Ceruloplasmin

glucose tolerance test (GTT, Oral glucose tolerance test [OGTT])

α1-antitrypsin

Albumin

Diagnostic Laboratory Tests for Mycobacterium Tuberculosis

Glucose, blood (Blood sugar, Fasting blood sugar [FBS])

Gliadin, endomysial, and tissue transglutaminase antibodies

Antimicrobial Susceptibility Testing and Therapy of Staphylococcus, Micrococcus, and Similar Organisms

Glucagon

genetic testing (Breast cancer [BRCA] and ovarian cancer, Colon cancer, Cardiovascular disease, Tay–Sachs disease, Cystic fibrosis, Melanoma, Hemochromatosis, Thyroid cancer, Paternity [parentage analysis], Forensic genetic testing)