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2.11: Glucose Tolerance Test

  • Page ID
    120228
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    RELATED READING: Chapter 32. See Methods in CD-ROM for Glucose.

    OBJECTIVES

    Upon completion of this exercise, appropriate discussion, and related reading, the student will be able to:

    1. Explain how to perform a Glucose Tolerance Test (GTT) for Gestational Diabetes.
    2. Construct a graph showing the relationship of time to serum glucose concentration.
    3. Perform calculations that allow evaluation of a glucose tolerance test.
    4. Discuss the possible physiological status of the patient that would produce the observed results.
    5. Determine urine glucose concentrations (Optional).

    PROCEDURE

    1. Perform glucose determinations on the patient samples provided using the procedure given in the previous exercise (#10). Each student will have GTT samples from one patient drawn at the following intervals: fasting, 60 min., 120 min., 180 min. The determination of urine glucose levels is an optional activity. Your instructor will give you specific instructions dealing with that procedure.
    2. Perform glucose determinations on the urine samples provided with your GTT samples and record the results on the data sheet (optional).
    3. Plot the results of serum glucose (mg/L, Y or vertical axis) vs. time (hours, X or horizontal axis) to establish a Glucose Tolerance Curve. Using the discussion of the O’Sullivan-Mahan test (as modified by Carpenter-Coustan) in Chapter 32 determine if the patient has gestational diabetes. The test uses a 100-g glucose load. Cut-off criteria for a normal response to this test are: fasting 950 mg/L, 1-hour 1800 mg/L, 2-hour 1550 mg/L, 3-hour 1400 mg/L. Two or more of the plasma glucose values must be equaled or exceeded for a diagnosis of gestational diabetes.
    DATA SHEET, EXERCISE #11

    NAME: ___________

    DATE: ___________

    Absorb. 525 nm Calculated Glucose Value (mg/L) Target Glucose Value (mg/L) Urine Glucose (Optional) (mg/L) Exceeds limits?
    Standard
    Normal Control
    Abnormal Control
    Fasting
    1 Hr.
    2 Hr.
    3 Hr.

    Discussion Questions

    1. What do the results of your glucose values, the O’Sullivan-Mahan test and graph suggest regarding this patient?
    2. Do the urine glucose values you obtained correspond to the serum values in the expected manner? Explain.
    3. What are the advantages and disadvantages of using a 3 hr. post-prandial evaluation instead of a 4 or 5 hour tolerance test?

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    2.11: Glucose Tolerance Test is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts.

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