CARBOHYDRATES LAB Flashcards
Specimens for carbohydrate analysis:
Whole blood, plasma, serum, urine, CSF, synovial, serious fluid
standard clinical specimen
fasting venous plasma
T or F: Serum is appropriate for glucose analysis if it is separated from the cells immediately after centrifugation
(approximately 60 minutes after blood collection)
F; approximately 30 mins
Bacteria, WBC, RBCs might consume the glucose present in the sample which can ____ the glucose results
lower
What should be used if processing will be delayed for more than 30 minutes?
sodium fluoride
Mechanism of action of fluoride in preventing glycolysis
Fluoride binds to magnesium, inhibiting enolase which is necessary for glycolysis
If whole blood is refrigerated, ______/mL of whole blood prevents glycolysis for up to ____hours
2 mg of NaF; 48
Fasting blood sugar should be obtained after ____ of fasting (but not >16hrs)
8-10 hours
CSF glucose concentration is approximately ______that of plasma concentrations.
60%-70%
How many hours should blood glucose be obtained before spinal tap?
1-2 hours
T or F: Peritoneal fluid glucose is the same as plasma glucose
T
Whole blood gives approximately ____LOWER glucose levels than serum or plasma.
10-15%
Venous blood glucose is 7mg/dL ____ than capillary blood glucose due to tissue metabolism
lower
T or F: Capillary blood glucose is not the same with arterial blood glucose
F; it is the same
Rate of glucose metabolism at RT
7 mg/dl/hr
At ___, glucose decreases by approximately 2mg/dl/hr.*
4 deg. Celsius
T of F: The rate of metabolism is lower with bacterial contamination or leukocytosis.
False; higher
In serum specimens without bacterial contamination or leukocytosis, results are clinically acceptable up to ______
90 minutes before separation of serum from cells.
Glucose methodologies can be categorized into:
Chemical and Enzymatic methods
Methodologies under Chemical method
Copper reduction, Ferric reduction, condensation method
Principle of copper reduction method
glucose and other reducing sugars convert cupric to cuprous ions in the presence of heat and alkali
Why is Folin Wu method sensitive but NOT SPECIFIC?
Because non-glucose reducing substances also react with the test
End color of Folin Wu
Phosphomolybdenum BLUE
Why is Nelson Somogyi method BOTH sensitive and specific
Because after PFF preparation, non- glucose reducing substances are adsorbed by BARIUM SULFATE
end color of Nelson Somogyi method
Arsenomolybdenum BLUE
end color of neocuproine method
Cuprous-Neocuproine Complex (YELLOW or YELLOW-ORANGE)
Which method is a modification of the Folin Wu?
Benedict’s method
stabilizing agents used in Benedict’s
citrate and tartrate
Positive and negative result for Benedict’s
(+) Green - yellow - brick red ppt
(-) blue
It is the modern version of Benedict’s method
Clinitest tablet
What sample is used in clinitest tablet
Urine
Phenomenon that occurs in clinitest tablet test when there is increased glucose level
PASS THROUGH PHENOMENON
Other term for Ferric Reduction method
Hagedorn jensen method
Principle of ferric reduction method
Inverse Colorimetry (reduction of yellow ferricyanide to colorless ferrocyanide)
Disappearance of color is measured at which wavelength
400 nm
Which method is employed in autoanalyzers
Ferric reduction method
Principle of condensation method
The aldehyde group of glucose condenses with aromatic amines in hot acetic acid solution to form colored derivatives
It is the most specific non-enzymatic method for glucose measurement
Orthotoluidine method / Dubowski method
disadavantage of Dubowski method
carcinogenic and teratogenic
end color of Dubowski method and at which wavelength is it measured
bluish green; 620-630 nm
3 enzyme systems commonly used to measure glucose
glucose dehydrogenase, glucose oxidase, and hexokinase
Percentage of alpha and beta glucose
Alpha - 35%
Beta - 65%
Enzyme involved in conversion of alpha to beta glucose
mutarotase
principle of glucose dehydrogenase method
amount of reduced nicotinamide adenine dinucleotide is proportional to glucose concentration in the sample
end color of glucose dehydrogenase method
blue
Why is glucose oxidase method the most specific enzymatic method?
It reacts only with Beta-d-glucose
The coupled reaction involved in glucose oxidase method is known as ___
TRINDER’S REACTION
Reducing agents causing falsely decreased results (13)
Oxidizing agents causing falsely increased results (2)
Reducing agents: uric acid, ascorbic acid, bilirubin, glutathione, creatinine, formalin, hemoglobin, tetracycline, l-cysteine, l-dopa, dopamine, methyldopa, and citric acid
Oxidizing agents: bleach and detergents
In polarographic method, ____ is measured and is proportional to the amount of glucose present
oxygen depletion
H2O2 is prevented from re-forming O2 by adding:
molybdate, iodide, catalase and ethanol
Why glucose oxidase is NOT the reference method?
Glucose oxidase is very specific, it only measures beta-glucose
Glucose oxidase is affected by reducing and oxidizing agents
REFERENCE METHOD/ GOLD STANDARD TEST
hexokinase method
principle of hexokinase method
glucose concentration is proportional to the rate of production of nicotinamide adenine dinucleotide phosphate (NADPH)
Wavelength used for hexokinase method
340 nm
hexokinase method can be performed on serum or plasma collected using
heparin, EDTA, fluoride, oxalate, or citrate
Is hexokinase method, specific or non specific?
It is non specific because any sugar with 6 carbon units will react with the test (fructose, glucose, galactose)
Analogy:
RBG: _____
_____: Screening
Monitoring; FBG
RBG is requested during:
Insulin Shock
Hyperglycemic Ketonic Coma
EMERGENCY CASES
There is a fast increase in the glucose level approxmately how many minutes after a meal?
30 minutes
blood glucose level normalizes within ___
2 hrs
In 2 hr PPBG, how many grams of glucose should be administered, and when should the sample be drawn?
75 g of glucose, after 2 hours
also referred to as CHALLENGE test
GTT
Procedure for Janney Isaacson method
Procedure:
Fasting blood and urine samples are obtained
Glucose load is given
Blood and urine samples are collected for glucose measurements 30 minutes, 1 hour, 2 hours and 3 hours after
Procedure for Exton Rose method
Procedure:
Fasting blood and urine samples are obtained
Glucose load is given
Blood and urine samples are collected for glucose measurements 30 minutes, 1 hour, 2 hours and 3 hours after
how many grams of glucose in ___ mL of water is used in double dose method?
100 g; 650 mL
Expected added plasma glucose after:
30 mins, 1 hr, 2hr, and 3 hr
30 mins: 30-60 mg/dL above fasting
1 hr: 20-50 mg/dL above fasting
2 hr: 5-15 mg/dL above fasting
3 hr: fasting level or below
Requirements for OGTT
- Patient should be ambulatory (mobile)
- The test should be performed after an overnight 8 to14-hour fasting (not longer than 16 hours)
- Unrestricted diet of 150 g of CHO per day for 3 days prior to testing
- Individual should not eat food, drink tea, coffee, or alcohol, or smoke cigarettes during the test, and should be seated.
Glucose load for:
Adults, pregnant women (suspected of GDM), and for children
Adults: 75 g
Preg: 100 g
Children: 1.75 g/kg of body weight
which GTT is used for diabetics with GIT d/o
IVGTT
glucose load for IVGTT, and time of glucose load administration and sample collection
0.5 g/kg of body weight; within 3 minutes; 5 mins after glucose administraiton
Indications for the use of IVGTT:
Unable to tolerate large carbohydrate in the diet
🞑 Presence of altered gastric physiology
🞑 Previous operation or surgery of the gastrointestinal tract
🞑 Presence of chronic malabsorption syndrome
INTERPRETATION OF RESULTS FOR FASTING BLOOD GLUCOSE
Non Diabetic: < 100mg/dL
Impaired FBS: > 100mg/dl but < 126 mg/dL
Diabetes Mellitus: > 126 mg/dL
INTERPRETATION OF RESULTS FOR ORAL GLUCOSE TOLERANCE TEST
Normal OGTT (2hr Glucose): < 140 mg/dL
Impaired OGTT (2hr Glucose): 140-199 mg/dL Diabetes Mellitus (2hr Glucose): > 200 mg/dL
DIAGNOSTIC CRITERIA FOR DIABETES MELLITUS
RBG: > 200 mg/dL with symptoms of DM
FBG: > 126 mg/dL
2-hr Post Prandial: > 200 mg/dL
HbA1c : > 6.5%
T: F glycosylated Hgb is more reliable than RBG for monitoring SHORT TERM glucose control
F; long term
SOC for glycated hemoglobin
non fasting whole blood drawn in EDTA
reference range for HbA1c
4-6%
T of F: for every 1% change in HbA1c value, 35 mg/dl is added to plasma glucose level
T
Any condition associated with shorted red blood cell survival will ____ the HbA1c level as the result of ____
Lower; reduced exposure to plasma glucose
Conditions associated with low HbA1c level due to shortened RBC survival
Hemolysis
Recovery from acute blood loss
Transfusions
Splenectomy
most widely used to assess short-term glycemic control
fructosamine (glycated albumin)
time interval for glycated hemoglobin and fructosamine
2-3 months; 3-6 weeks
When should fructosamine not be performed?
When the serum albumin level is low (<3.0 mg/dL)
specimen for POCT
whole blood capillary glucose
how does hematocrit affect POCT glucose measurements
High Hct = lower glucose
Procedure for One Step Method for GDM
- Collect fasting plasma (8 hours)
- Give 75 g glucose load
- Collect plasma after 1 and 2 hours
Criteria for diagnosis of GDM using One - Step method
Fasting: >- to 92 mg/dL
1 hr: >- to 180 mg/dL
2 hr: >- to 153 mg/dL
Procedure for Two Step method for GDM
Step 1: 1. Give 50 g of glucose to non fasting patient 2. Collect plasma after 1 hr 3. If plasma glucose level is >140 mg/dl, proceed to Step 2, if not stop Step 2 : 1. Collect fasting plasma (8hrs) 2. give 100 g of glucose load 3. Collect plasma after 1,2, and 3 hours
Criteria for diagnosis of GDM using Two Step
Accdg to Carpenter: Fasting: >- 95 mg/dL 1 hr: 180 mg/dL 2 hr: 155 mg/dL 3 hr: 140 mg/dL
Accdg to NDDG: Fasting: >- 105 mg/dL 1 hr: >190 mg/dL 2 hr: >-165 mg/dL 3 hr: >-145 mg/dL
