Pregnant women should be screened for diabetes mellitus sometime between the 24th and 28th week of gestation.
(1) Starting 3 days prior to test, the patient receives a diet containing 150 g of carbohydrate per day.
(2) The patient must not be stressed by illness prior to or during the test.
(3) All nonessential medications should be discontinued at least 3 days prior to testing; many medications can impair glucose tolerance.
(4) A 10-16 hour fast is recommended.
(5) Undue exercise before or during the test is to be avoided.
(6) No coffee or smoking is allowed once the fast has started or during the test.
Dose of glucose for test:
(1) screening test: 50 grams orally
(2) diagnostic test: 100 grams orally
Oral glucose solutions come in 10 US fluid ounces (296 mL) bottles containing 50, 75 or 100 grams of glucose (5, 7.5 and 10 g per fluid ounce).
50 gram oral screening test:
The serum glucose is measured 1 hour after the dose and if it exceeds the cutoff then the 100 gram diagnostic test is performed:
(1) The cutoff prior to 1997 was >= 150 mg/dL.
(2) The current cutoff is >= 130 mg/dL
100 gram oral diagnostic test:
The diagnosis of gestational diabetes requires that at least 2 glucose values exceed the cutoffs for various times.
Cutoffs for the 100 g oral test from the National Diabetes Data Group (NDDG)
Current cutoffs for the 100 g oral test (after Carpenter and Coustan)
• Glucose in whole blood is 90% of that in serum or plasma.
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Purpose: To evaluate the 100 gram oral diagnostic test for gestational diabetes.
Specialty: Endocrinology, Clinical Laboratory
Objective: laboratory tests
ICD-10: R73.0, O24.4,