test directorySearch Results
Click here to search again.
Test Name:
Glucose Tolerance, Modified (ADA), Non-Gestational
- SBMF No:
29056 - Performance Lab Name:
Automated Lab - Test Mnemonic:
GTT - ABN:
Not required - CPT Code:
82947; 82950 - LOINC Code:
1558-6; 12610-2 - Test Includes:
Fasting glucose test result
75 g glucose dose (adults)
2-hour post-glucose test result (2 samples total) - Also Known As:
GTT
Tolerance, Glucose
OGTT
Modified Glucose Tolerance
Oral Glucose Tolerance - Also See:
29129 – Glucose, Plasma
29004 – Glucose Challenge, 50 g, Gestational
29057 – Glucose Tolerance, Gestational - Spec Type:
Plasma - Spec Container:
Light green top (PST) tube - Alt Spec Type:
Plasma - Alt Spec Container:
Gray top (fluoride/oxalate) tube
Note: Although not preferred, serum samples are acceptable, but must be removed from cells within 60 minutes of collection and refrigerated - Pref Vol:
1.0 mL - Min Vol:
0.3 mL - Fasting:
Yes - Patient Prep:
Fasting at least 8 hours; 12-hour fast is preferred; fasting should not exceed 14 hours
At least 3 days prior to sample collection, patient should consume an unrestricted diet containing at least 150 grams of carbohydrates, unless physician advises against it
The patient may drink only water during test
Dozing, smoking, gum chewing and exercise are not permitted during the test
Refer to patient instruction sheet and suggested diet - Spec Collect:
Routine venipuncture
Collect at specified times:
– Fasting sample (pre-glucose dose)
– 2-hour sample (post-glucose dose) - Spec Process:
PST or gray top tubes:
– Promptly centrifuge 15 minutes and refrigerate
Gold top or red top tubes:
– Clot 30 minutes
– Promptly centrifuge 15 minutes
– Within 60 minutes of collection, transfer serum to separate plastic tube and refrigerate - Spec Store Transport:
Refrigerated - Spec Stability:
1 week refrigerated (2-8°C) - Spec Reject:
Plasma or serum in contact with RBC more than 1 hour - Spec Remarks:
For diagnostic purposes, plasma samples are recommended, rather than serum. Plasma glucose results are generally 5% lower than serum and the cutoff values for diagnostic testing, as recommended by the ADA study, were established using plasma. The reference ranges posted on SBMF glucose reports are also based on plasma studies.
Urine specimens will not be routinely collected and tested for the tolerance test
- Methodology:
Photometric - Use:
Establish the diagnosis of diabetes mellitus in the non-pregnant adult patient or in children - Clinical Significance:
Based on recommendations made in 2002 by the Expert Committee of the American Diabetes Association (ADA) and by the World Health Organization (WHO), South Bend Medical Foundation has adjusted testing procedures and interpretative data for diabetes testing as summarized below.- Recommendations for Diagnosing Type 1 and Type 2 Diabetes
- Fasting Plasma Glucose (FPG)
- – FPG less than 110 mg/dL = normal fasting plasma glucose level
– FPG equal to or greater than 110 and less than 126 mg/dL = impaired fasting plasma glucose level
– FPG equal to or greater than 126 mg/dL = provisional diagnosis of diabetes; confirm on subsequent day
When the FPG is in the impaired fasting glucose range (110-126 mg/dL), a modified oral glucose tolerance test is recommended, consisting of a fasting and a 2-hour post-glucose plasma sample.- Glucose Tolerance, Modified (ADA), Non-Gestational
- Testing should be performed after at least three (3) days of an unrestricted diet. Schedule the test for the morning following an overnight fast for the patient of at least 8 hours, but not more than 14 hours.
– Dosage (unless the physician order instructs otherwise):- Children (<12 years of age): 1.75 g/kg body weight; maximum dose is 75 g
Adults: 75 g- Criteria for adult glucose tolerance testing have been revised so that cutoff values for the fasting plasma glucose and 2-hour post-glucose results reflect a similar degree of hyperglycemia. The criteria are also meant to facilitate and encourage use of the simpler, and equally accurate, fasting plasma glucose (FPG) for diagnosing diabetes. During the non-gestational glucose tolerance, two specimens, an FPG and a 2-hour plasma glucose (PG), will be collected (unless the physician order instructs otherwise).
The result of the 2-hour PG specimen should be interpreted as follows:
2-hour PG less than 140 mg/dL = normal glucose tolerance
2-hour PG equal to or greater than 140 and less than 200 mg/dL = impaired tolerance
2-hour PG equal to or greater than 200 mg/dL = provisional diagnosis of diabetes - Reference Range:
Fasting plasma glucose (FPG) result: Less than 110 mg/dL
2-hour plasma glucose (PG) result: Less than 140 mg/dL - Day Run:
Mon-Sat - Time Run:
As received - Time Reported:
Same day - Test Type:
CHEMISTRY
