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Test Code 2 Hr GTT 2 Hour Glucose Tolerance Test, Non-Gestational

Aliases

2 Hour Glucose Tolerance Test, 75 g (Care Set)

Useful For

Diagnosis of diabetes type 1 / 2

Patient Preparation

8 to 14 hour fast after 3 days of normal carbohydrate (>150 g/day) diet. Perform only if fasting glucose is <150 mg/dl.

Special Collection Instructions

  1. Draw fasting venous specimen.
  2. Give 75 g glucola.
  3. Draw venous specimen at 2 hours post consumption.

Collection Method

Venous collection

Minimum Volume

  • Adult: 0.4 mL
  • Pediatric: 0.25 mL

Container

Grey Top / Sodium Fluoride Potassium Oxalate

Preferred Specimen

Grey (Sodium Flouride/Potassium Oxalate)

Acceptable Specimens

Serum:

  • Gold Top SST
  • Red Top


Plasma:

 

  • Light Geen Top (lithium heparin)

 

Reference or Target Ranges

Fasting (adult) 70 – 99 mg/dL
2 hour (adult) 70 – 139 mg/dL
  Impaired Tolerance Diabetes
Fasting 100 – 125 mg/dL >125
2-Hour 140 – 199 mg/dL >199

Reportable Units

mg/dL

Critical Value

Infants <1 months <40 mg/dL or >300 mg/dL
Others <40 mg/dL or >400 mg/dL

Reasons for Rejection

Hemolysis Threshold 1000 mg/dL
Icterus Threshold 60 mg/dL
Lipemia Threshold 1000 mL
Other QNS, contaminated, improperly Labeled, improper specimen type

Specimen Stability

Ambient 8 hours (if collected in SodiumFlouride/Potassium Oxalate tube)
Refrigerated (4°C to 8°C) 3 days
Frozen(-40°C to 0°C) Not listed

Performance Information

Days and Time Performed 24/7
Expected Turn Around Time 1 hour
Stat Availability No
Performing Bench UH Chemistry, WCH Chemistry
Methodology/Method Description Roche Cobas – Glucose Hexokinase

Special Handling

Centrifuge within 2 hours of collection if collected in PST/SST/Serum tube

CPT Codes

82947, 82590