Diabetes mellitus is a group of metabolic diseases characterized by the high blood sugar (glucose) level that results from defect in insulin secretion or its action or both. It can lead to blindness, kidney failure and nerve damage.Thirst, polyuria, blurring of vision and weight loss are the symptoms of Diabetes.

Blood sugar level- The prime source of energy for all the animal and human cells is glucose which is a kind of sugar which passes through the blood system. The level of glucose is kept normal by glucagon and insulin. Insulin is the hormone which is generated in the pancreas and discharged into the blood system when the level of glucose rises. The blood sugar level in the normal adult ranges from 70-100 mg/dl during fast and less than 140 mg/dl after consuming glucose. The blood sugar level in diabetic patients is more than 126 mg/dl during fast and exceeds to 200 mg/dl after consuming glucose.

Glycosylated hemoglobin is a form of hemoglobin that is measured primarily to identify the average plasma glucose concentration over the prolonged period of time. This test is not used to detect diabetes. It is more important to judge the control of diabetes during a period of 6-10 weeks prior to the test, in a person undergoing treatment for the disease. The haemoglobin present in the red blood corpuscles has a tendency to get bound to glucose. The greater the blood-glucose concentration, the greater is the amount of glucose-bound (glycosylated) haemoglobin. If the amount of glycosylated hemoglobin is between 6-8% the control of diabetes is excellent. If the range is 8-10%, then the result is satisfactory. But if the glycosylated hemoglobin rises above 12% it is impossible to control diabetes. This is a sign of danger.

There are several different types of blood glucose test. They are:

i) Fasting blood sugar (FBS)- it measures the blood glucose level during fast. The patients are not allowed to eat for at least 8 hours. It is often the first test done to check the pre-diabetic and diabetic status.

ii) Postprandial blood sugar- it measures the blood glucose level exactly 2 hours after consuming the meal. This test does not diagnose diabetes.

iii) Random blood sugar (RBS)- it measures the blood glucose level regardless of food consumption by the patient. Several random measurements may be taken throughout the day. Random testing is useful because the glucose level in healthy people do not vary widely throughout the day.

iv) Oral glucose tolerance test- it is used to diagnose pre-diabetes and diabetes. An oral glucose tolerance test is a series of blood glucose measurements taken after consuming a sweet liquid that contains glucose. This test is commonly used to diagnose diabetes that occurs during pregnancy (gestational diabetes).

v) Glycohemoglobin A1c- it measures how much sugar (glucose) is stuck to the red blood cells. This test can be used to diagnose diabetes. The result of A1c test can be used to estimate the average blood sugar level. The normal values are 4% to 6%. The level for pre-diabetic are 6% to 6.5%. the level more than 6.5% indicates diabetes.

Hyperglycemia is a condition in which the blood glucose level rises above the normal range. This results in diabetes, overactive thyroid gland, pancreatic cancer, pancreatitis, rare tumors like glucagonoma. Hypoglycemia is a condition in which the blood glucose level depreciates than the normal value. The disorders of this condition are fatal like, hypopituitarism (a pituitary gland disorder), underactive thyroid gland, insulinoma (a very rare condition).
The pancreas is an organ in the abdomen that makes several enzymes and hormones, including the hormone insulin. When the blood sugar level drops too low, the pancreas stops making insulin until the blood sugar level returns to normal. Insulinoma is a condition in which pancreas produces too much insulin. Insulinoma keep making insulin, even when the blood sugar level is low.

At the level over 240 or higher, the risk of diabetic coma is prominent. Ketoacidosis can occur when the body does not have enough insulin to breakdown glucose and therefore the body begins to use stored fat for energy. This process causes the development of ketones in our body which is toxic in nature. The body can not release all the ketones and as they build up in the blood system, they create the condition of ketoacidosis which leads to diabetic coma and even death.

Now, lets focus on the procedure of collection of blood sample for estimating the blood glucose level. The peripheral blood samples collected from the adults needed for laboratory testing, with proper specimen identification and handling, while ensuring patient and staff safety is important. Proper collection of an appropriate clinical specimen is the first step in obtaining an accurate laboratory diagnosis. The sample should be collected in the area specified for sample collection having appropriate table and chair with arm rest and should be sent to the laboratory for specified tests. The laboratory staff is responsible for collection of blood samples. The officer- incharge implements the Standard Operating Procedure (SOP) by providing specific training and thereafter by inspections. The equipments required for the blood sample collection are disposable gloves, alcohol swabs, isopropyl alcohol / spirit, tourniquet, vacutainer specimen tubes, vacutainer holders, appropriate size sterile disposable needles, cotton balls or swabs, sharps disposal container, markers and centrifuge machine.

In the hematology tests, liquid EDTA is used as an anticoagulant. The clotted blood make the test invalid so the addition of an anticoagulant is compulsory. Invert the sample tube 7 to 10 times to prevent clotting.

The phlebotomist must be highly carefull while puncturing the skin for collecting blood. Obtain capillary blood from fingertips or earlobes (adults) or from the great toe or heel (infants). Disinfect the puncture site and dry the site with cotton swab. The skin should be punctured with the sterile disposable needle and wipe away the initial drop of blood. Collect the subsequent drops of blood in a microtube or prepare a smear directly from a drop of blood.
The blood samples collected should be in a particular order. Date and time should be mentioned when the samples were taken. For immediate storage, aliquoted samples need to be labelled with subject identifier, date of sample collection, visit number and sample type. Assign the box numbers to aid location in the freezers. Freeze the blood sample at -80ºC. Samples should ideally be sent as soon as they are obtained. If the samples cannot be sent immediately then they should be stored at ambient temperature for a maximum period of one week before sending. Generally, samples are transported every three months or when there is sufficient number of samples. During transportation the boxes containing blood samples are packaged properly with sufficient dry ice to ensure samples do not thaw or leak.

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Geetanjali Murari
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