Module 2: Carbohydrates Obj. 5 Flashcards
difference in glucose values between serum/plasma and whole blood
glucose in whole blood is 10% less than serum/plasma
length of time required for a patient to be considered fasting
8-16hrs
preferred handling requirement for serum/plasma samples
refrigerated and separated from cells within 1-2 hours
collection preservative that should be used if glucose testing is significantly delayed
Sodium fluoride (grey top) inhibits glycolysis
role of glucose measurement in CSF samples
help to identify bacterial meningitis
2 main methods for measuring glucose
Glucose oxidase: glucose is oxidized to form H2O2
Hexokinase method: hexokinase in presence of ATP converts glucose to G-6-P
form of glucose that glucose oxidase is specific for
beta-D-glucose
2 measurement techniques that can be used in glucose oxidase methods, and which is more susceptible to interferences
amperometry: measure rate of oxygen disappearance using oxygen electrode (avoids pos/neg interferences of chromogenic method)
H2O2 produced used with reagent peroxidase enzyme to produce a coloured product
reason the hexokinase method is considered more accurate (reference method)
coupling reaction using G-6-P dehydrogenase is more specific and has less interference
what is actually measured in the hexokinase method, including wavelength
NADPH is measured at 340nm
describe 2 hr post-prandial test for glucose
patient drinks 75g glucose load. Measurement is taken 2 hours later. Some facilities may take fasting glucose prior to test (should be less than 7.8mmol/L; it above that, test is not performed)
Provide the reference range for fasting serum/plasma glucose and for a 2 hour PP value
Fasting: 3.3-6.0mmol/L
Random: 3.3-11.0mmol/L
2hPP: less than 6.7mmol/L
2hPP CL: less than/equal to 2.5mmol/L
2hPP CH: more than/equal to 25.0mmol/L
state the approximate difference in values from serum for arterial/capillary and CSF samples
CSF is about 60% of plasma glucose levels
