Glucose Tolerance 2 Hour, Modified (ADA), Non-Gestational

Glucose Tolerance 2 Hour, Modified (ADA), Non-Gestational

Alternate Test Name

2 Hour Glucose Tolerance
GTT
OGTT
Modified Glucose Tolerance
Oral Glucose Tolerance
Tolerance, Glucose

Epic Mnemonic
Sunquest Mnemonic

LAB169
2GTT

Category

Chemistry

Methodology

Enzymatic; Hexokinase

Test Performance Schedule

Sunday-Saturday

Result Availability

Within 24 hours

Container

Gold top (SST), Green top (lithium heparin) or Lavender top (EDTA) tube

Volume

Pref. Vol.: 1.0 mL serum or plasma
Min. Vol.: 0.3 mL serum or plasma

Collection Instructions

• Routine venipuncture
• Collect at specified times:
» Fasting sample - preglucose dose
» 2 hour sample - postglucose dose

Gold Top:
• Clot 30 minutes
• Immediately centrifuge 15 minutes
• Within 60 minutes of collection, transfer serum to separate plastic tube
• Refrigerate



DIET INSTRUCTIONS PRIOR TO GLUCOSE TOLERANCE TEST

Transportation Instructions

Refrigerate for up to one week at 2-8° C

Stability

• Room Temperature: 8 hours
• Refrigerated: 3 days

Causes for Rejection

Serum or plasma in contact with cells (unspun) for more than 2 hours
Gross Icterus

Remarks

Test Includes:
• Fasting glucose test result
• 75g glucose dose (adult)
• 2-hour post-glucose test result (2 samples total)

Patient Preparation:
• Fasting at least 8 hours; 12-hour fast is preferred; fasting should not exceed 14 hours
• At least 3 days prior to sample collection, ambulatory patients should receive appropriate Lakeland Instruction sheet regarding test preparation and diet requirements
• The patient may drink only water during test
• Dozing, smoking, gum chewing and exercise are not permitted during the test

Additional Test Information:
NOTE: Dosage for children (12 years of age or less) is 1.75g/kg body weight; maximum dose is 75g.

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), Lakeland has adjusted testing procedures and interpretative data for diabetes testing as summarized below:
• Recommendations for diagnosing Type 1 and Type 2 diabetes: Glucose Tolerance, Modified (ADA), Non-Gestational (75g adult dosage) Diagnostic Criteria: Criteria for adult glucose tolerance testing have been revised so that cutoff values for the fasting and 2-hour post-glucose results reflect a similar degree of hyperglucemia. The criteria are also meant to facilitate and encourage use of the simpler, and equally accurate, fasting glucose (GLUF) for diagnosing diabetes. During the non-gestational glucose tolerance, two specimens, a fasting glucose and a 2-hour glucose, will be collected. The result of the 2-hour glucose specimen should be interpreted as follows:
• 2-hour glucose less than 140mg/dL = normal glucose tolerance
• 2-hour glucose equal to or greater than 140mg/dL and less than 200mg/dL = impaired tolerance
• 2-hour glucose equal to or greater than 200mg/dL = provisional diagnosis of diabetes

CPT Codes

82951

Effective/Revised

3/24/2022