Carbohydrates -Analytical Methods for measuring Glucose - Cerebrospinal Fluid Glucose, Serum, Urine Glucose, Glycated Hemoglobin,
How long is the serum or plasma specimen good for?
-8 hours at 25 degrees C -72 hors at 4 degrees C
Plasma vs serum?
-Plasma = naturally found in body = anticoagulants added to get it this way -Serum = no anticoagulants = allowed to clot and doesnt contain fibrinogen Serum = plasma - fibrinogen (clotting factors)
CSF glucose < 40 mg/dL is indicative of what pathologies?
-bacterial meningitis -fungal meningitis -tuberculous meningitis -systemic hypoglycemia -cancers -impairment of glucose transport across blood brain barrier, ect
What are the two coupled reactions involved in the hexokinase system
1. Glucose + ATP -----------> G-6-PO4 + ADP (hexokinase) 2. G-6-PO4 + NADP -----------> 6-phosphogluconate + NADPH + H+ (glucose-6-phosphate dehydrogenase)
What other reducing substances besides other sugars can interfere with the clinitest?
1. creatinine (protein (seen in kidney disease) 2. uric acid 3. ascorbic acid aka vit C)
Results with whole blood a greater or less than those with serum or plasma (anticoagulated = has fibrinogen)
10% less than those with serum or plasma due to having more water content?
Glucose level in CSF
40-70mg/dL
specimen shelf life for Glycated hemoglobin
4C 1 week = whole blood 4C 4 to 7 days or -70 30 days = hemosylate
HbA1c Range
5.7-6.4%
What is an adapted procedure for Benedict's Principle?
Clinitest Tablets (yellow is pos, blue is neg)
Glycated hemoglobin needs to be collected with what anticoagulants
EDTA, heparin, or fluoride
(March 8th 2018 - on page 169 of Anderson Chemistry Book) Whole blood used for glucose testing allowed to sit out for an hour is still a good specimen to use? True or False? And Why?
False - glucose is metabolyzed by the cells in the specimen at a rate of about 7% at roo temp
What is the most accepted reference method for glucose determination
Hexokinase enzyme system
is the clinitest specific for glucose?
NO (glucose, fructose, maltose, lactose, xylose, ribose, arabinose, ect, all react = all reducing sugar)
Does hemolysis interfere with the hexokinase system? Explain why or why not?
RBC contain G-6-Phosphate dehydrogenase (used as enzyme in second step of reaction )and 6-P-gluconate dehydrogenase use NADP+ as a substrate and would then have the results appear much lower because there would be less NADP+ available for glucose to be phosphorylated with
Is glucose a reducing substance?
YES BETCHHHHHHH, only sucrose isn't a reducing sugar
False negatives for urine strips are caused by
ascorbic acid and urates that inhibit reduction reaction?
What is the name of the reaction that the urine glucose methedology is based on ?
benedict's copper reduction reaction urine strips don't use Benedict's, but color idea is similar...use chomagen and oxidizing agen ... https://www.youtube.com/watch?v=wJykz_Eg1G4 ... (blue is negative...yellow or red is positive...yellow + blue = green, and blue + red = purple...get an orange/red/ green color for positive)
How long is urine good for for a glucose analysis?
ehhhhh not very long -can be preserved for 24 hours
what is used to preserve urine glucose?
glacial acetic acid or sodium benzoate must be added to container BEFORE collection
Principle for urine glucose test
greducing sugars like glucose reduce cupric ions to cuprous ions and forms a yellow or red color ... Blue is negative for glucose = negative for reducing substances (reduce means add electrons, so elemental charge is reduced) ...
Urine strips are better than the clinitest because?
more specific for glucose
False positives occur with urine strips due to
oxidizing substances, such as 1. bleach (hypochlorite), and hydrogen peroxide
What preservatives are used to keep glucose stable for 24 hours at room temp?
sodium fluoride, fluoride-oxalate, iodoacetate
when no preservatives are used, serum or plasma must be separated from the cells w/in how long after blood is drawn?
w/in 1 hour - to prevent glucose metabolization by cells