Blood Glucose Testing

Clinical Pathology (JAA) Blood Glucose Testing Sometime in December Introduction • Blood sugars: fructose, galactose, glucose • Glucose is the primary source of energy of cells • Plasma glucose is maintained within narrow limits during fasting and postprandial state by insulin and counter regulatory hormones such as glucagon • Normally 4 – 8 mmol/L (70 – 150 mg/dl) • High = hyperglycemia e.g. impaired glucose tolerance or diabetes mellitus • Low = hypoglycemia e.g. fasting, insulinoma

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Specimen Considerations • Venous plasma glucose – standard • Serum, whole blood • Plasma or serum glucose levels are 15% higher than whole blood glucose

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Metabolized 7 mg/dL/h at 4oc

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Higher w/ bact contamination, leukocytosis Serum should be separated w/in 30 min (90 min if w/o bact contam) Stable in ref for 48 hrs

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Methods • Enzymatic methods o Glucose dehydrogenase o Glucose oxidase o Hexokinase – reference method • Electric current is produced proportional to initial glucose concentration • Product measured spectrophotometrically Diabetes Mellitus • Chronic disorder of carbohydrate, fat, protein metabolism due to absolute or relative deficiency of insulin • Complications - blindness, kidney disease, gangrene, heart disease, stroke

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•

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>200 mg/dL (11.1 mmol/L) or higher, diagnostic

of DM OGTT

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BUT: fasting below 126 mg/dL (7.0 mmol/L) and

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2 hr value > 140 mg/dL (7.8 mmol/L) but < 200 mg/dL (11.1 mmol/L) = IMPAIRED GLUCOSE TOLERANCE Fasting glucose >110 mg/dL (6.1 mmol/L) but < 126 mg/dL (7.0 mmol/L) = IMPAIRED FASTING GLUCOSE

Diagnosis of Pre-Diabetes and Diabetes Mellitus Fasting Plasma Glucose

Fasting plasma glucose level > 126 mg/dl (7.0 mmol/L) on at least 2 occasions; 8 hr fast

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Symptoms

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polydipsia, polyphagia, unexplained wt loss) w/ casual plasma glucose level of > 200 mg/dL (11.1 mmol/L) 2-hr plasma glucose value 200 mg/dl or higher following a 75-g oral glucose tolerance test (OGTT) OGTT not recommended for routine clinical use Indicated:

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Equivocal fasting or random plasma glucose concentrations o Diagnosis of impaired glucose tolerance or gestational diabetes o Epidemiologic studies to determine DM prevalence o Px’s w/ clinical features of DM or complications w/ normal blood glucose OGTT prep: o Eat normal diet ~ 150 g CHO/day x 3 days o Discontinue meds (diuretics, steroids, oral contraceptives) o Be ambulatory o Fast overnight (8- 14 hrs) o Conducted between 7 am – 12 pm o Patient is rested, seated o No smoking o Drinking water allowed o Collected in gray tube w/ fluoride and anticoagulant OGTT Procedure o Basal blood sample o Give 75 gm glucose in 250-300 ml water orally o Blood sample taken at 120 min o

of

hyperglycemia

MR*, Eisa, Mel

(e.g.

polyuria,

(di ko na alam kung ano ittrans)

Normal Prediabetes Impaired fasting glucose Impaired glucose tolerance Daibetes mellitus

mg/dL