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Test Code 3 Hr GTT Glucose Tolerance Test, Gestational Diagnostic

Aliases

3 Hour GTT, 3 Hour Glucose Tolerance Test, 100 g (Care Set)

Useful For

Diagnosis of gestational diabetes

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 specimen.
  2. Give 100 g glucola.
  3. Draw venous specimen at 1, 2, 3 hours post consumption.

Collection Method

Venous collection

Minimum Volume

0.4 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 <95 mg/dL
1 hour <180 mg/dL
2 hour <155 mg/dL
3 hour <140 mg/dL

Reportable Units

mg/dL

Critical Value

<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 Stat: 1 hour
Routine: 4 hours
Stat Availability Yes
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

Additional Information/Important Notes

This entry is for the 3 hour glucose tolerance test careset. For shorter intervals, the same reference values apply. For shorter durations, see Navex for instructions on Glucola dosing

Diagnostic criteria are met when glucose exceeds 2 or more of the cited cut-offs.

CPT Codes

82591, 82952