Most Common Tests for Glucose

Glucose- also known as dextrose- is the most predominant carbohydrate. The glucose level in the blood is affected by diet through the food that we eat like carbohydrates (rice, bread, starch, etc.)

Blood glucose levels are usually tested in fasting samples of patients- Fasting Blood Sugar (FBS). The patient is required to fast for 8-12 hours before blood is extracted for testing. On certain occasions, Random Blood Sugar (RBS) or non-fasting samples are required too.

Oral Glucose Tolerance is also done in borderline suspected Diabetes Mellitus (DM) patients; sometimes an HbA1C test is done to monitor compliance to medication of patients.

Although automated procedures employing the enzymatic principle of glucose assays are now being adapted by many clinical laboratories, the manual method using the Orthotoluidine method is still useful. Some manual methods employ the oxidation-reduction property of glucose to measure its concentration.

In the Orthotoluidine method utilizes the principle of the condensation of aromatic amines by glucose to form a green end product which is then measured spectrophotometrically.

Unhemolyzed, non-icteric, non- tubid and non- lipemic serum is the best specimen. Serum is the supernatant fluid when coagulated blood is centrifuged. If an anticoagulant is used EDTA (ethylenediaminetetraacetic acid) is preferable.

The specimen and the orthotoluidine reagent is mixed and then boiled for 5-8 minutes, and then the absorbance or transmittance is read in the spectrophotometer. The reading will then be computed based on the absorbance /transmittance of unknown and standard and computed.

This formula is used to determine Cu (concentration of unknown):

Cu= Absorbance of Unknown/ Absorbance of Standard X Concentration of standard (Cu=Au/As X Cs)

This will give you the concentration in milligrams per deciliter. To convert this to mmol/L multiply it with 0.0555 (conversion factor)

The oral glucose tolerance test (OGTT) on the other hand, measures the body's ability to metabolize glucose. This test is used to diagnose borderline diabetes and also determines gestational diabetes mellitus (GDM) in pregnant women.

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DIABETES MELLITUS

CLINICAL SIGNIFICANCE OF ELEVATED BLOOD GLUCOSE

Diabetes Mellitus

When the pancreas produces insufficient insulin or no insulin at all, Diabetes Mellitus results. This is because insulin is responsible in maintaining the normal blood glucose levels by several processes that allow the body’s tissues to absorb glucose and utilize it as energy or store it for future use.

Diabetes Mellitus is characterized by what is called the classical triad, or the three P's - polyuria, polydyipsia and polyphagia. Other symptoms also are hyperglycemia and glycosuria among others. This condition can affect several organs in the body.
For more information visit this site: MedicineNet.com

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ORAL GLUCOSE TOLERANCE TESTS

The oral glucose tolerance test (OGTT) measures the body's ability to metabolize glucose. This test is used to diagnose prediabetes and diabetes and to determine gestational diabetes in pregnant women.

Patient Preparation:

* Regular diet containing least 150 to 200 grams of carbohydrate per day is
observed for 3 days prior to the test.

* Medications should be referred to the doctor whether to stop or continue taking
them.

* Alcohol and cigarettes are not allowed at least 8 hours before blood collection.

* Strenuous exercise also is to be avoided at least 8 hours before blood collection.

* No unnecessary activities ( doing errands, manual labor) should be done during the
duration of the test.

* The patient is allowed water.

* If the fasting blood sugar is between 100-130 mg/dL, then OGTT is recommended.
Ranges higher than this, FBS is recommended.

* The patient should be ambulatory.

* The test should be performed in a hospital where a resident doctor can respond to
any emergencies.

* For polycystic ovary syndrome, a Glucose tolerance test screening is usually
performed at age 30 and above.

* Urine and fasting blood specimens should be tested first, before proceeding with
the test.

CARBOHYDRATES

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Carbohydrates are the main source of energy for the body. Sources of carbohydrates are rice, bread, pasta, corn, and many more. When ingested they are reduced to monosaccharide by the body's biochemical processes.

The most predominant monosaccharide is glucose. Glucose- also known as dextrose- is the sugar tested in the clinical laboratory when a person requests for a blood sugar test.

Blood glucose levels are maintained in the body at 60-100 mg/dL and this level is maintained through the body's homeostatic ability.

When the glucose levels increase the primary hormone that decreases this levels is insulin. On the other hand, the primary hormone that increases glucose levels when it is below normal, is glucagon. Both of these hormones are produced by the pancreas in the beta and alpha cells of the Islets of Langerhans, respectively.

Since blood glucose levels are affected by diet through the food that we eat, fasting is required before a test is performed( except in cases of RBS - Random Blood Sugar).

Fasting hours for 8-12 hours is done prior to the extraction of blood.

In the colorimetric method of glucose determination, visit the link below for full information and example:
Bioassaysys.com