Diabetes Mellitus Urine Testing

Diabetes Mellitus Urine Testing

Discuss briefly the laboratory diagnosis of diabetes mellitus.
Or
Write short notes on diagnostic tests of diabetes mellitus.
Or
Write a brief on investigating methods in the diagnosis of diabetes mellitus.
Answer:

Diabetes Mellitus Urine Testing

These tests are cheap and convenient, but the diagnosis of diabetes cannot be based on urine testing alone since there may be false positives and false-negative results. They can be used in population screening surveys. Urine is tested for the presence of glucose and ketones.

1. Glucosuria

• Benedict’s qualitative test detects any reducing substance in the urine and is not specific for glucose. A more sensitive and glucose-specific test is the dipstick method based on an enzyme-coated paper strip, which turns purple when dipped in urine containing glucose. Besides diabetes mellitus, glucosuria may also occur in certain other conditions, such as—renal glycosuria, alimentary (lag storage) glucosuria, and many metabolic disorders. However, two of these conditions—renal glucosuria and alimentary glucosuria, require further elaboration.
• Renal glucosuria: Next to diabetes, the most common cause of glucosuria is the reduced renal threshold for glucose. In such cases, although the blood glucose level is below 180 mg/dl, glucose still appears regularly and consistently in the urine due to lowered renal threshold.
• Alimentary (lag storage) glucosuria: A rapid and transitory rise in blood glucose levels above the normal renal threshold may occur in some individuals after a meal. During this period, glucosuria is present.

Urine test for diabetes

2. Ketonuria

Tests for ketone bodies in the urine are required for assessing the severity of diabetes and not for the diagnosis of diabetes. However, if both glucosuria and ketonuria are present, the diagnosis of diabetes is almost certain.

• Rothera’s test (nitroprusside reaction) and strip test are conveniently performed for the detection of ketonuria.

Diabetes Mellitus Single Blood Sugar Estimation

For the diagnosis of diabetes, blood sugar determinations are necessary. Currently used are O—toluidine, Somogyi—Nelson, and glucose oxidase methods.

Whole blood or plasma may be used, but whole blood values are 15% lower than plasma values. A grossly elevated single determination of plasma glucose may be sufficient to make the diagnosis of diabetes.

A fasting plasma glucose value above 126 mg/dl is indicative of diabetes.

Glucose in urine diabetes

Diabetes mellitus Screening by Fasting Glucose Test

Fasting plasma glucose determination is a screening test for type 2 diabetes mellitus. It is recommended that all individuals above 45 years of age must undergo a screening fasting glucose test every 3 years.

Diabetes Mellitus Oral Glucose Tolerance Test

It is performed principally for patients with borderline fasting plasma glucose values (i.e., between 100 and 140 mg/dl).

The patient who is scheduled for an oral glucose tolerance test is instructed to eat a high carbohydrate diet for at least three days before the test and come after an overnight fast on the day of the test.

A fasting blood sugar sample is first drawn. Then 75 gm of glucose dissolved in 300 mL of water is given. Blood and urine specimens are collected at half-hour intervals for at least 2 hours.

Blood or plasma glucose content is measured, and urine is tested for glucosuria to determine the approximate renal threshold for glucose.

Urine sugar test procedure

Diabetes mellitus Other Test

A few other tests are sometimes performed in specific conditions in diabetics and for research purposes:

• Glycosylated hemoglobin (HbA1c): Measurement of blood glucose level in diabetics suffers from variation due to dietary intake of the previous day. Long-term objective assessment of the degree of glycemic control is better monitored by measurement of glycosylated hemoglobin (HbA1C), a minor hemoglobin component present in normal persons (normal range 4–6%). This is because the non-enzymatic glycosylation of hemoglobin takes place over 90-120 days, the lifespan of red blood cells. HbA1C assay, therefore, gives an estimate of diabetic control and compliance for the preceding 3-4 months.
• Glycated albumin: This is used to monitor the degree of hyperglycemia during the previous 1-2 weeks when HbA1C can not be used.
• Extended GTT: The oral GTT is extended to 3-4 hours for the appearance of symptoms of hyperglycemia. It is a useful test in cases of reactive hypoglycemia of early diabetes.
• Intravenous GTT: This test is performed in persons who have intestinal malabsorption or in postgastrectomy cases.
• Cortisone­primed GTT: This provocative test is a useful investigative aid in cases of potential diabetics.
• Islet autoantibodies: Glutamic acid decarboxylase and islet cell cytoplasmic antibodies may be used as a marker for type I DM.