A 42 year old male has strong positive Benedict’s test, random blood sugar is > 163 mg%, fasting blood sugar is >200 mg% Next line of investigation is-
Correct Answer: OralGTT
Description: Urine testing Glucose -Testing the urine for glucose with dipsticks is a common screening procedure for detecting diabetes. If possible, testing should be performed on urine passed 1-2 hours after a meal to maximise sensitivity. Glycosuria always warrants fuher assessment by blood testing (see below). The greatest disadvantage of urinary glucose measurement is the individual variation in renal threshold for glucose. The most frequent cause of glycosuria is a low renal threshold, which is common during pregnancy and in young people; the resulting 'renal glycosuria' is a benign condition unrelated to diabetes. Another disadvantage is that some drugs (such as b-lactam antibiotics, levodopa and salicylates) may interfere with urine glucose tests. Ketones -Ketone bodies can be identified by the nitroprusside reaction, which measures acetoacetate, using either tablets or dipsticks. Ketonuria may be found in normal people who have been fasting or exercising strenuously for long periods, who have been vomiting repeatedly, or who have been eating a diet high in fat and low in carbohydrate. Ketonuria is therefore not pathognomonic of diabetes but, if associated with glycosuria, the diagnosis of diabetes is highly likely. In diabetic ketoacidosis (p. 811), ketones can also be detected in plasma using test sticks (see below). Protein -Standard dipstick testing for albumin detects urinary albumin at concentrations above 300 mg/L, but smaller amounts (microalbuminuria, see Box 17.13, p. 476) can only be measured using specific albumin dipsticks or by quantitative biochemical laboratory measurement. Microalbuminuria or proteinuria, in the absence of urinary tract infection, is an impoant indicator of diabetic nephropathy and/or increased risk of macrovascular disease (p. 830). Blood testing Glucose- Laboratory glucose testing in blood relies upon an enzymatic reaction (glucose oxidase) and is cheap, usually automated and highly reliable. However, blood glucose levels depend on whether the patient has eaten recently, so it is impoant to consider the circumstances in which the blood sample was taken. Blood glucose can also be measured with colorimetric or other testing sticks, which are often read with a poable electronic meter. These are used for capillary (fingerprick) testing to monitor diabetes treatment (p. 810). There is some debate as to whether selfmonitoring in people with type 2 diabetes improves glycaemic control. Many countries now only offer selfmonitoring to people with type 2 diabetes taking blood glucose concentration should be estimated using an accurate laboratory method rather than a poable technique.Glucose concentrations are lower in venous than aerial or capillary (fingerprick) blood. Whole blood glucose concentrations are lower than plasma concentrations because red blood cells contain relatively little glucose. Venous plasma values are usually the most reliable for diagnostic purposes (Boxes 21.10 and 21.11). Ketones -Blood ketone monitoring is increasingly available. Urinary ketone measurements described above are semi-quantitative, difficult to perform and retrospective (i.e. the urine has accumulated over several hours), and do not measure the major ketone in blood during diabetic ketoacidosis (DKA), beta-hydroxybutyrate (bOHB). Whole blood ketone monitoring detects b-OHB and is useful in assisting with insulin adjustment during intercurrent illness or sustained hyperglycaemia to prevent or detect DKA. Blood ketone monitoring is also useful in monitoring resolution of DKA in hospitalised patients (Box 21.7). Glycated haemoglobin Glycated haemoglobin provides an accurate and objective measure of glycaemic control integrated over a period of weeks to months. In diabetes, the slow non-enzymatic covalent attachment of glucose to haemoglobin (glycation) increases the amount in the HbA1 (HbA1c) fraction relative to nonglycated adult haemoglobin (HbA0). These fractions can be separated by chromatography; laboratories may repo glycated haemoglobin as total glycated haemoglobin (GHb), HbA1 or HbA1c. In most countries, HbA1c is the preferred measurement. The rate of formation of HbA1c is directly propoional to the ambient blood glucose concentration; a rise of 1% in HbA1c corresponds to an approximate average increase of 2 mmol/L (36 mg/dL) in blood glucose. Although HbA1c concentration reflects the integrated blood glucose control over the lifespan of erythrocytes (120 days), HbA1c is most sensitive to changes in glycaemic control occurring in the month before measurement. DAVIDSONS PRINCIPLES AND PRACTICE OF MEDICINE 22ND EDITION PAGE NO-807,808
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