South Bend Medical Foundation - Your Community Laboratory

test directorySearch Results

Click here to search again.

Test Name:
Glucose Tolerance, 3-Hour, Gestational, with 100g Glucose Load

• SBMF No:
  29057
• Performance Lab Name:
  Automated Lab
• Test Mnemonic:
  GTTP DIAG
• ABN:
  Not required
• CPT Code:
  82951; 82952
• LOINC Code:
  1558-6; 12646-6; 12610-2; 18342-6
• Test Includes:
  Fasting glucose test result
  100 g glucose dose
  1-, 2-, and 3-hour post-glucose test results (4 samples total)
• Also Known As:
  Gestational Glucose Tolerance Test
  Pregnancy Glucose Tolerance
• Also See:
  29129 Glucose, Plasma
  29004 Glucose Challenge, 50 g, 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
• Spec Collect:
  

  Routine venipuncture
  Collect at specified times:

  • Fasting sample (pre-glucose dose)
  • 1-, 2-, and 3-hour samples (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 (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 pregnant patient
• 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 Gestational Diabetes
  ADA and WHO continue to recommend an oral glucose tolerance test for establishing the diagnosis of gestational diabetes, however, the following modifications have been made to the recommendations:
  Low-risk patients do not require testing. Low-risk status applies to women with all of the following criteria:
  – Age less than 25 years
  – Weight normal before pregnancy
  – Member of an ethnic group with a low prevalence of gestational diabetes
  – No known diabetes in first-degree relatives
  – No history of abnormal glucose tolerance
  – No history of poor obstetric outcome
  High-risk patients should undergo immediate testing. This applies to women with any of these criteria:
  – Marked obesity
  – Personal history of gestational diabetes
  – Glycosuria
  – Strong family history of diabetes
  Average-risk patients (falling between low-risk and high-risk) should be tested at 24-28 weeks of gestation
  
  
  A one-step approach, accomplished by performing the gestational oral glucose tolerance test, may be most effective in high-risk women. In average-risk patients, a two-step approach can be employed beginning with the gestational 50 g glucose challenge.
  Glucose Challenge, 50 g, Gestational
  – Dosage: 50 g
  – Diagnostic Criteria:
  1-hour PG equal to or greater than 140 = positive screen
  Recommend follow-up 100 g Diagnostic Test
  Glucose Tolerance, Gestational
  – Dosage: 100 g
  – Diagnostic Criteria:
  Considered diagnostic, if two or more plasma glucose (PG) results meet the following criteria:
  Fasting PG equal to or greater than 95 mg/dL
  1-hour PG equal to or greater than 180 mg/dL
  2-hour PG equal to or greater than 155 mg/dL
  3-hour PG equal to or greater than 140 mg/dL
  • Reference Range:
    GTT interpretation in pregnancy with a 100g glucose load
    Diagnostic of gestational diabetes if two or more of glucose results meet the following criteria:

    Fasting 1 hour 2 hour 3 hour

    >= 95 mg/dL >= 180 mg/dL >= 155 mg/dL >= 140 mg/dL

  • Day Run:
    Mon-Sat
  • Time Run:
    As received
  • Time Reported:
    Same day
  • Test Type:
    OBSTETRIC-NEONATAL