Chapter III Laboratory Tests and MonitoringLABORATORY PROCEDURES The diagnosis of diabetes mellitus has been primarily dependent upon the results of specific glucose tests, along with a physical examination, presence or absence of symptoms, and a medical history. The two main tests used to measure the presence of blood sugar irregularities are the direct measurement of glucose levels in the blood during an overnight fast and measurement of the body’s ability to appropriately handle the excess sugar presented after drinking a high glucose drink. In June 1997, the American Diabetes Association devised new criteria for the diagnosis of diabetes. The blood glucose level considered to be normal was lowered and new recommendations for when to test for diabetes were put into place. The new criteria for diagnosis are as follows:
The classic symptoms of diabetes include:
Along with changing the diagnostic criteria for diabetes, two new categories have been added. Impaired fasting glucose (IFG) is when fasting plasma glucose is found to be at or above 110mg/dl but below 126mg/dl. The second category is when the results of the oral glucose tolerance test (OGTT) are between 140mg/dl in the 2-hour sample. This is called impaired glucose tolerance (IGT). Patients in these two categories need to be monitored closely since they are at a higher risk for developing diabetes as well as hypertension and heart disease. Criteria for who should be tested have also changed. The following should be tested:
BLOOD SUGAR MONITORING In order to establish an insulin treatment plan, it is essential that blood sugar levels are checked at various times to determine how each part of the treatment plan is working. The blood sugar results help identify adjustments needed in insulin, food and exercise to achieve better control of the disease process. Reasons for blood sugar fluctuations are:
There are two common ways that physicians may assess how well diabetes is being controlled. They are:
Combined, these tests give a fairly accurate picture of the state of glucose control in a diabetic. Frequent Measurements of Blood Glucose Blood glucose levels can be measured randomly (RBS) from a sample taken any time or it can be measured in the fasting state. A fasting blood glucose sample is taken when the patient has not eaten in the past 8 hours and is usually done overnight. In a patient with normal insulin production, blood glucose levels return to normal fasting levels within 3 hours of eating. After a meal, diabetics are not able to return to a normal fasting level within a 3-hour period. The goal is to keep fasting blood sugars under the 140mg/dl or lower (in the 70-120mg/dl range) Measurements of Glycohemoglobin Hemoglobin A1c or Glycohemoglobin (or glycosylated hemoglobin) is used to access blood sugar levels over a 2-3 month period. The level of hemoglobin A1c correlates with the patient’s recent overall blood sugar levels. If blood sugar levels have been running high the previous month, the level of hemoglobin A1c will be high. Values in the better ranges are consistent with fewer incidences of diabetic complications in later life. Type 1 diabetics will usually have hemoglobin A1c levels drawn every 3 to 4 months, while Type 2 diabetics will often require measurements less frequently. Values vary from lab to lab. Below are common values for Hemoglobin A1c. Blood Glucose monitoring provides data for the patient and the health care team to:
Increase the frequency of blood glucose checks:
Keeping a log book The patient should keep a record of their glucose values in a logbook. The records should include:
SELF-MONITORING OF BLOODD GLUCOSE Self-monitoring blood glucose (SMBG) is used as a guide to diabetes control. SMBGs is a direct method of monitoring blood glucose level. SMBG allows the health care provider and the patient to determine the pattern of blood glucose levels and make necessary changes in diet, exercise, or the insulin dose. SMBG measures precisely the effects of changes in diet, exercise, and insulin dosage as they relate to blood glucose levels. The immediate information made available by SMBG helps in avoiding insulin reactions and allows for a rapid response to an elevation or decline in blood sugar, and can be used as a basis for treatment. BLOOD GLUCOSE LEVELS
Using Glucose Monitoring as a Tool The patient should be taught the following in order to use glucose monitoring to their best advantage.
URINE TESTS Testing for Ketones in Urine (Type 1 Diabetes) When there is not enough insulin present to channel glucose into the cells, the body uses stored far to make fuel available to the cells. The fat in fat cells is broken down to fatty acids, which pass through the liver and form ketones (acetone). Ketones are exhaled and excreted in urine. Aa blood sugar greater than 200 along with ketones in the urine is a warning sign of a low insulin level and requires immediate action. Ketostix, Chemstrip UK, or Ace test tablets can be used to test for ketones. Testing for Glucose in Urine Urine testing is still used despite the invention of SMBG because it is easy, painless, non-invasive, and inexpensive. This is important for people on fixed incomes or for those whose insurance policies do not cover the strips used in SMBG. The result of the urine test indicates the concentration of glucose in the urine. The higher the result of the urine test, the higher the concentration of glucose in the urine. Test results with vary from1/2% to 5% depending on the concentration of glucose. |