Glucose tolerance test

The oral glucose tolerance test ( glucose tolerance test, also briefly OGTT) used for the detection of impaired glucose utilization and the diagnosis of diabetes mellitus. In overt diabetes mellitus it is contraindicated.

The oral glucose tolerance test is used in a modified form for the diagnosis of other endocrine disorders ( GH suppression test in acromegaly, extended OGTT for up to 6 hours of suspected hypoglycaemia eg, insulinoma ).

Principle of the Test

Idea is to determine the blood glucose - regulating ability of the body with the help of a strong stimulation by recorded sugar. For this purpose is used glucose dissolved in water, as it is the form of sugar that can accommodate the fastest of the body and leads to a sharp rise in blood glucose concentration (equivalent to the determination of a system response in systems theory ). Stimulated by this increase in blood sugar, the pancreas regulates the secretion of insulin against which stimulates hypoglycemic reactions in the liver, muscle and fat cells. During the OGTT is periodically over time the blood sugar value, possibly the insulin value measured: fasting value, rise, maximum and drop in blood sugar up on fasting value.

With an OGTT regulating the body's ability in strength and the speed can be determined, which allows diagnostic statements with appropriate benchmarks. For example, in a delayed decrease in fasting glucose levels are closed to insulin resistance or reduced Insulinsekretionsfähigkeit, at too high maximum glucose values ​​or failure to achieve a fasting glucose level within a defined period on a strong diabetes mellitus.

Indication as a diagnostic method

The WHO recommends the OGTT as a diagnostic tool in general, also contrary to concerns about effort and cost. This is justified by the poor sensitivity of a pure fasting glucose level determination; According cited DECODE study about 30 % of diabetics are not thereby detected. Also could be discovered only through a oGTT impaired glucose tolerance (IGT ).

The German Diabetes Society (DDG ) proposed in the 2007 Directive kürzerintervalliges screening with an OGTT if the following risk factors are present:

  • Type 2 diabetes mellitus in first-degree relatives
  • Obesity and physical inactivity
  • Arterial hypertension ( blood pressure ≥ 140/90 mmHg)
  • Dyslipoproteinemia with HDL cholesterol ≤ 35 mg / dL and / or triglycerides ≥ 250 mg / dL
  • State after gestational diabetes or birth of a child with birth weight > 4000 g
  • Earlier detection of impaired glucose tolerance (IGT ) or impaired fasting glucose ( IGF)
  • Macrovascular diseases
  • Albuminuria

It should also be noted that the HbA1c or fructosamine value for a diabetes screening are unsuitable.

Contraindications

Contraindications for the OGTT are according to the DDG intercurrent diseases (eg after gastrointestinal resection or gastrointestinal diseases with altered absorption ) or an already onset diabetes mellitus.

Action recommendation of the German Diabetes Society

According to the German Diabetes Association (DDG ) of the test is to be performed in the morning at ten hours before fasting patients. In order to obtain a meaningful result, the patient must be connected to the previous three days with at least 150 g of carbohydrates per day and have as yet fed ( no diet attempts to get a favorable result ). In addition, no febrile illness may be present in patients and has a three-day spacing before and will be adhered to menstruation. During the test, the patient must not eat, do not drink, do not smoke and not be physically active.

Commercially available instruments for blood glucose self-monitoring (up to 15% ) not authorized pursuant to the allowable fluctuation range of the measurement results for the diagnostics.

  • 0 min: blood for fasting glucose determination ( capillary or venous plasma)
  • Then, taking a defined amount of glucose (75 g, for children 1.5 g per kg body weight) were dissolved in 250-300 ml of water. The liquid must be drunk within 5 minutes.
  • Multiple blood for glucose determination ( capillary or venous plasma) after 60 min and 120 min, with extended test after every 60 minutes or such as the presence of a hypo.

OGTT and gestational diabetes

To establish a gestational diabetes test as part of preparedness 24 to 28 weeks' gestation can be performed. In Germany, this test is since March 2012 part of the maternity guidelines and thus a performance of the statutory health insurance.

Currently (as of March 2013) offer health insurance to test for their insured to:

  • AOK Plus
  • Barmer GEK
  • Betriebskrankenkasse Mobil Oil
  • Hkk

The offers of health insurance change frequently. In some cases there are also country-specific agreements between the physicians' associations and health insurance.

The American Diabetes Association (ADA ) recommends screening of gestational diabetes a 3 -hour OGTT ( 100 g glucose ), if a 1 -hour OGTT ( 50 g glucose) with a blood glucose level ≥ 140 mg / dl ( ≥ 7, 8 mmol / l) is striking. The criteria of Carpenter and O'Sullivan have a high sensitivity for a large range of women ( age, ethnicity, etc.), that are considered to be reliable indicators.

Interpretation

Possible confounders

An OGTT may be false positive in:

  • Taking medication (such as diuretics, laxatives, contraceptives)
  • Duodenal ulcer ( duodenal ulcer )
  • And v. a

To false negative results may result:

  • To low carbohydrate intake on the previous days
  • Malabsorption
  • Taking medications ( hypoglycemic )
  • Physical activity, smoking during the test phase
  • And v. a
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