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2. Glucose and Diabetes II

Terms in this set (25)

What is the most commonly used sample for glucose analysis?
serum or plasma
Why must serum/plasma be separated from cells within 1 hr of collection and refrigerated?
To prevent loss of glucose to cellular metabolism
How long should one be fasting for FPG?
8-10 hr
GOD-POD
-glucose oxidase peroxidase
1. beta-D-glucose + O2 + glucose oxidase -> gluconic acid + H2O2
2. H2O2 + reduced dye + peroxidase -> colored, oxidized dye + H2O
What are interfering substances that alter the 2nd reaction of GOD-POD?
-bleach
-ascorbic acid
How does bleach affect GOD-POD?
oxidizes the dye = falsely elevated
How does ascorbic acid (vitamin C) affect GOD-POD?
reacts with H2O2 = falsely decreased
What is the gold standard for glucose analysis?
hexokinase
Hexokinase method
1. D-glucose + ATP(Mg++) + hexokinase -> glucose-6-phosphate + ADP
2. glucose-6-P + NAD+(or NADP+) + G6PD -> 6-phosphogluconic acid + NADH(or NADPH) + H+
What is measured in the hexokinase method and at what wavelength?
Increase in absorbance of NADH or NADPH is measured at 340nm
What is an interference in the hexokinase method?
EDTA anticoagulant will bind to Mg++ = falsely decreased
Copper reduction method
-Benedict's copper reduction reaction
-glucose reduces cupric ions to cuprous ions to produce a yellow or red cuprous compound
Method of analysis for Hgb A1c
ion-exchange or affinity chromatography
ion-exchange chromatography
-Glucose attaches to the end of the beta chains in Hgb and ties up the amino group, changing the charge.
-Glycated Hgb are less positively charged at neutral pH than HbA and elute first. Non-glycosylated Hgb binds to the resin.
-Measure the amount of red color (glycohemoglobin)
-Glycated hemoglobin is calculated as a percentage of total Hgb
Disadvantages to ion-exchange
-abnormal Hgb (F, S, C, etc) have a different # of amino groups than Hgb A, so may bind or flow whether or not they are glycosylated
-False increase with increased Hgb A
-False decrease with RBC survival disorder
affinity chromatography
-All glucose molecules that have free OH groups on C4 and C5 will bind to boronic acid
-All glucose plus all glycosylated proteins will stick to the resin
-Non-glycosylated Hgb elutes through
Presence of autoantibodies to the beta islet cells of the pancreas is characteristic of Type _____ diabetes.
1
Lactate accumulation causes:
-increased anion gap
-depletion of bicarbonate
-metabolic acidosis
Lactic acidosis (type A)
Respiratory: decreased tissue oxygenation (hypoxia)
Lactic acidosis (type B)
Metabolic: associated w/ diseases like diabetes, drugs/toxins, inborn errors, metabolism
galactosemia
-deficiency of enzymes required to convert galactose to glucose
-leads to accumulation of galactitol (neurotoxic)
What is used to routinely detect galactosemia in patients <2 yrs old?
Clinitest (copper reduction test), even if glucose in urine is negative
Why isn't dipstick used for galactosemia?
Dipstick doesn't detect reducing sugars
Glycogen storage disorder (type 1)
-von Gierke's disease
-glucose-6-phosphatase deficiency
fructosuria
-fructose in urine
-defects in the enzymes involved in the metabolism of fructose
-diagnosis by chromatography
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