A medical test to determine the ability of an individual to maintain HOMEOSTASIS of Blood Glucose The most commonly performed version of the Test (OGTT)

History First described in 1923 by jerome W.conn( ) (Conn syndrome )

GDM International Association of Diabetes and pregnancy study groups (IADPSG) criteria American diabetes association(ADA)-2014

Screening for and diagnosis of GDM “One-step” (IADPSG consensus) Perform a 75-g OGTT, with plasma glucose measurement fasting and at 1 and 2 h, at 24–28 weeks of gestation in women not previously diagnosed with overt diabetes. The OGTT should be performed in the morning after an overnight fast of at least 8 h.

The diagnosis of GDM is made when any of the following plasma glucose values are exceeded: Fasting: ≥92 mg/dL (5. 1 mmol/L) 1 h: ≥180 mg/dL (10.0 mmol/L) 2 h: ≥153 mg/dL (8.5 mmol/L)

“Two-step” (NIH consensus) Perform a 50-g GLT (nonfasting), with plasma glucose measurement at 1 h (Step 1), at 24–28 weeks of gestation in women not previously diagnosed with overt diabetes. If the plasma glucose level measured 1 h after the load is ≥140 mg/dL* (10.0 mmol/L), proceed to 100-gOGTT (Step 2).

The 100-g OGTT should be performed when the patient is fasting. The diagnosis of GDM is made when the plasma glucose level measured 3 h after the test is ≥140 mg/dL (7.8 mmol/L). *The American College of Obstetricians and Gynecologists (ACOG) recommends a lower threshold of 135 mg/dL in high-risk ethnic minorities with higher prevalence of GDM.

OGTT is not an appropriate study for evaluating a patient suspected of having hypoglycemia. An OGTT is rarely necessary for the diagnosis of diabetes mellitus.

Recommendation for postpartum care in women with GDM to ruled out prediabetes or overt diabetes 2-hour,75g OGTT 6 to 12 weeks after delivery (nonpregnant OGTT criteria 2h ≥200mg/dl)

Two-hour PG ≥200 mg/dL ( 11.1 mmol/L) during an OGTT. The test should be performed as described by the WHO, using a glucose load containing the equivalent of 75 g anhydrous glucose dissolved in water *In the absence of unequivocal hyperglycemia, result should be confirmed by repeat testing..

Categories of increased risk for diabetes (prediabetes) FPG 100 mg/dL (5.6mmol/L) to 125 mg/dL (6.9 mmol/L) (IFG) OR 2-h PG in the 75-g OGTT 140 mg/dL (7.8 mmol/L) to 199 mg/dL ( 11.0 mmol/L) (IGT) OR A1C 5.7–6.4%

The Following conditions should be met before an OGTT is performed: Discontinue, when possible, medications Known to affect glucose tolerance Perforrm in the morning after 3 days of unrestricted diet & activity (diet containing at least 150g of carbohydrate per day ) After a 10 to 16 hour fast only in ambulatory outpatient (bed rest impairs glucose tolerance) (8-14hour)

Patient should remain seated during the test without smoking cigarettes Testing should use plasma glucose analyzed at a laboratory, not capillary blood glucose analyzed with a blood glucose meter GTT should not be performed on hospitalized, acutely ill or inactive patient The Test should begin between 7AM and 9AM. 75g anhydrous glucose/300ml water ingested over 5minutes

Factors Other Than Diabetes That Influence the Oral Glucose Tolerance Test Patient Preparation Duration of fast Prior carbohydrate intake Medications (e.g., thiazides, oral contraceptives, corticosteroids) Trauma Intercurrent illness Age Activity Weight

Administration of Glucose Form of glucose (anhydrous or monohydrate) Quantity of glucose ingested Volume in which administered Rate of ingestion During the Test Posture Anxiety Caffeine Smoking Activity Time of day Sample preservation

OGTT Indications 1- Diagnosis of GDM 2- Diagnosis of IGT (controversial ) 3- Evalution of a patient with unexplained nephropathy, neuropathy or retinopathy with random PG <140 mg/dl 4- Population studies for epidemiologic data