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Epic Code LAB1230091 Glucose Tolerance, 3 hour test, 100g (Gestational Diabetes Diagnostic)

Important Note

  • For outpatient collection: Providers please instruct patient to arrive at least 4 hours prior to the lab closing to ensure there is enough time to complete the test.
  • This test is recommended and only available for pregnant patients.
  • Fasting specimen required -  A fasting glucose specimen will be drawn.

Test Name Alias

Oral Glucose | 3 hr, Glucose Tolerance, Glucose | GTT | OGTT | 177 | 1230100111 | 1230100112|1230100115 |1230102386

Interface Order Alias

1230091

Ordering Instructions

This test is recommended as a follow-up or confirmatory test for an abnormal One Hour Post (50 gram) OGTT.

 

This test is recommended and only available for PREGNANT patients.

 

For safety and accuracy of testing, patients are encouraged to have Oral Glucose Tolerance Tests (OGTT) performed at one of our Outpatient Service Centers.

Collection Instructions

  • A fasting glucose specimen will be drawn.
  • The patient is given a 100 gram oral glucose load.
  • Another specimen is drawn 1, 2 and 3 hours later.
  • GlucoCrushTM, the glucola drink used in Spectrum Health Grand Rapids Laboratory does not contain gluten.

 

Specimen Collection: Blood

 

Container(s): Gray Top (Potassium Oxalate and Sodium Fluoride)

  • Also acceptable: Light Green Top (Lithium Heparin Gel) OR 5.0 mL Gold Top (Serum Separator-SST Gel)
  • Minimum Volume to Collect: 1.0 mL
  • Neonate Volume to Collect: 0.5 mL
  • Capillary collect ok? Yes
  • Microtainer acceptable: Yes

Collection Instructions:

  • Fasting specimen required
  • After collection, gently invert tube 8-10 times.
  • Gray top whole blood is preferred specimen type
  • If collecting green or gold top:
    • Specimen should be processed within 2 hours – See Processing Instructions.
    • Processed Specimen: Plasma or Serum
    • Centrifuge/Spin: Yes
    • Aliquot: Yes
    • Processing Instructions:
      • Gold Tube/Serum: Allow blood to clot for 30 minutes in a vertical position and centrifuge within 2 hours.
      • Green Tube/Plasma: Centrifuge after collection.
      • Minimum plasma/serum volume: 0.5 mL

Transport Temperature: Refrigerated

 

Lab Central Instructions:

  • Centrifuge Gray-top tubes before delivery to the appropriate testing station.

Specimen Stability

Ambient: 8 hours

Refrigerate: 72 hours

Frozen: aliquot plasma/serum for longer storage

Laboratory Retention: 72 hours

Test Frequency

Available daily, usual TAT 1 day.

Reference Range

  • Glucose Fast (3) 70 - 95 mg/dL
  • Glucose 1 Hr (3) ≤179 mg/dL
  • Glucose 2 Hr (3) ≤154 mg/dL
  • Glucose 3 Hr (3) ≤139 mg/dL

 

Glucose 3 Hr Gestational GTT 100G Interpretation

  • Negative:  3-hour Glucose Tolerance Testing does not support a diagnosis of Gestational Diabetes.  Based off of ADA guidelines, the test is negative if none or only one of the Glucose results are elevated.
  • Positive:  3-hour Glucose Tolerance Testing supports a diagnosis of Gestational Diabetes.  Based off of ADA guidelines, the test is positive if two or more of the Glucose results are elevated.         

Performing Department

Chemistry

Performing Department Laboratory Location

CHW: Corewell Health Reference Laboratory, Grand Rapids, MI
CHS: Corewell Health Lakeland St. Joseph Laboratory, St. Joseph, MI

Methodology

Enzymatic

CPT

82952, 82951, 82952, 82947

CDM Code

3018295201
3018295101
3018295201
3018294701

Epic Test ID

1230100111,
1230100112,
1230100115,
1230102386

LOINC

Currently not available

Reviewed Date

3/7/2024

Updated Date

3/14/2024 - Reference Range

5/13/2025 - CHS info added

Orderable Regions

Southwest; West