Gestational Diabetes Screen (ACOG Recommendations)

CPT: 82950
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Test Details

Synonyms

  • Glucose Tolerance, Gestational Diabetes (One-hour)

Test Includes

50-gram one-hour glucose tolerance challenge

Use

Screening test for gestational diabetes

Methodology

Enzymatic

Contraindications

Patient with known history of diabetes mellitus

Reference Interval

65−139 mg/dL

Critical Value

<40 mg/dL or >500 mg/dL

Additional Information

The American College of Obstetricians and Gynecologists (ACOG) recommends that all pregnant women be screened for gestational diabetes mellitus (GDM)—whether by patient history, clinical risk factors, or with a 50-gram, one-hour loading test at 24 to 28 weeks of gestation to determine blood glucose levels—and suggests relying on the result of the 100-gram, three-hour oral glucose tolerance test for diagnosis (often referred to as a "two-step" method).2

The American Diabetes Association (ADA)3 released standards that vary from the ACOG recommendations. The ADA recommends a simplified "one-step" approach to the screen and diagnosis of gestational diabetes mellitus with a 75-gram, two-hour glucose tolerance test. The LabCorp test according to the ADA recommendations is Gestational Glucose Tolerance Screening and Diagnostics Test (Two-hour, ADA Recommendations) [101000]. A glucose tolerance screen glucose threshold >139 mg/dL after a 50-gram load identifies approximately 80% of women with gestational diabetes mellitus, while the sensitivity is further increased to approximately 90% by a threshold >129 mg/dL. Perform a diagnostic 100-gram oral glucose tolerance test (102004) on a separate day on women who exceed the chosen threshold on 50-gram screening.

Specimen Requirements

Specimen

Serum or plasma

Volume

1 mL serum or plasma each tube

Minimum Volume

0.5 mL serum or plasma each tube

Container

Gel-barrier tube or gray-top (sodium fluoride/potassium oxalate plasma) tube

Patient Preparation

None; glucose challenge is administered without regard to time of day or time of last meal.

Collection

Note: A fasting blood sample is not required. Draw one hour specimen after a 50-gram glucose challenge. The patient should remain seated and not smoke throughout the test. Submit 1 mL serum or plasma for one-hour specimen. Separate serum or plasma from cells within 45 minutes of venipuncture. Gray-top tubes only, may be submitted without centrifugation. Label tube with patient's name and collection time interval (ie, one-hour).

Storage Instructions

Maintain specimen at room temperature.1

Stability Requirements

Temperature

Period

Room temperature

14 days

Refrigerated

14 days

Frozen

14 days

Freeze/thaw cycles

Stable x3

Causes for Rejection

Frozen gray-top tube (frozen plasma from gray-top is acceptable); stressed patient (surgery, infection, corticosteroids) should not have GTT; specimen not labeled with collection time intervals (i.e., one hour)

Clinical Information

Special Instructions

The patient need not be fasting. The one-hour screen requires a 50-gram oral glucose load followed by a plasma glucose determination one hour later. (Refer to Additional Information below.) See the online Endocrine Appendix: Glucose Tolerance: Gestational Diabetes Mellitus for further information regarding glucose tolerance testing.

Footnotes

1. LabCorp internal studies.
2. American College of Obstetricians and Gynecologists. Committee on Practice Bulletins—Obstetrics. Practice Bulletin N° 137: Gestational diabetes mellitus. Obstet Gynecol. 2013 Aug; 122(2 Pt 1):406-416. 23969827
3. American Diabetes Association. Standards of Medical Care in Diabetes—2015: Summary of revisions. Diabetes Care. 2015 Jan; 38(Suppl 1):S4. 25537706

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
102277 Gest. Diabetes 1-Hr Screen 1504-0 102285 Gestational Diabetes Screen mg/dL 1504-0

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