Glucose Flashcards
Specimen Collection and Storage: normal hematocrit
whole blood glucose is 10-12% lower than plasma glucose
Specimen Collection and Storage: Capillary blood glucose
2-5 mg/dl higher than venous blood
Possible samples glucose method
Serum
CSF
Whole Blood
Synovial Fluid
Urine
Standard specimen glucose method
Fasting venous sample
Specimen Consideration
Uncentrifuged coagulated blood
Prolonged standing: 7 mg/dL per hour (RT)
Separated nonhemolyzed sterile serum
Specimen consideration: Uncentrifuged coagulated blood
Lower 5-7 % in 1 hour
Specimen Consideration: Prolonged
standing
- 7 mg/dL per hour (RT)
- 40C - 1-2 mg/dL per hour
Specimen Consideration: Separated nonhemolyzed sterile serum (25oC)
8 hrs
Specimen Consideration: Separated nonhemolyzed sterile serum (40oC)
72 hrs
CHOICE OF SAMPLE:
Serum should be separated from the clot within 0.5 to 1 hour
NaF: 2mg/ml of blood or iodoacetate
NaF - 2 mg for up to 48 hrs
Binds with Ca and Mg
inhibition of enolase
Precautions in sample collection to prevent glucose utilization by leukocytes (WBC)
RBC have all the enzymes necessary to metabolize glucose
The sample should be kept cool
Other samples for glucose testing urine sample reagent
5 mL glacial acetic acid
5g sodium benzoate (24 hr specimen)
Chlorhexedine
0.1% sodium nitrate w/ 0.01% benzethonium chloride
Tests for Glucose
Measurement
Random Blood Sugar
Fasting Blood Sugar (FBS)
Two-hour post prandial test (PPBS)
Glucose Tolerance Test
Oral glucose tolerance test
Requested during insulin shock and hyperglycemic ketonic coma.
Random blood sugar
The test should be performed after an 8 hour fast
Fasting blood sugar
The test is performed two hours after meal
2 hrs post prandial test
Used to determine how well the body metabolizes glucose over a required period of time
Glucose tolerance test
Used for diagnosis of gestational diabetes
Glucose tolerance test
Glucose tolerance test is used to diagnose
Gestational diabetes
Not generally recommended for routine clinical use for diagnosis of DM
Glucose tolerance test
Kinds of Glucose Tolerance
Tests
Oral Glucose Tolerance Test
Intravenous Glucose Tolerance Test
Oral glucose tolerance test 2 types
Janney-isaacson method
Exton rose method
Most common single dose method oral glucose tolerance test
Janney-isaacson method
Divided oral dose or double dose method oral glucose tolerance test
Exton rose method
Janney-isaacson method AKA
Single dose method
Exton rose method AKA
Divided oral dose
Double dose method
Used for DM patients with gastrointestinal disorders
Intravenous glucose tolerance test
Intravenous glucose tolerance test used for dm patient with
Gastrointestinal disorder
Intravenous glucose tolerance test body weight
0.5 g of glucose/kg of body weight
Oral glucose tolerance test Requirements:
• Patient must be ambulatory
• Patient to be tested should ingest at least 150 g of CHO 3 days prior to testing
• Patient should not eat food, drink tea, coffee or alcohol, vigorously exercise, or smoke cigarettes during the test
• Patient must fast the night before the testing is performed
Procedure for
OGTT
Collect the fasting blood sample
Instruct the patient to drink the glucose load
Collect blood sample after 1°, 2° and 3°
Categories of Oral Glucose Tolerance
Normal glucose tolerance
Impaired glucose tolerance
Provisional diabetes diagnosis
Normal glucose tolerance value
2-h PG < 140 mg/dl
Impaired glucose tolerance value
2-h PG 140-199 mg/dl
Provisional diabetes diagnosis value
2-h PG > 200 mg/dl
If the 1 hour postload glucose level is 140 mg/dL (7.8 mmol/L), a complete _______ three-hour oral glucose tolerance test should be performed
100g
TEST USED TO DIAGNOSE
GESTATIONAL DIABETES a _______ oral glucose load is recommended as basis of initial
diagnosis.
50 g
CRITERIA USED TO DIAGNOSE
DIABETES: FBS level that is greater than or equal to ____________ (7.0 mmol/L) on at least 2 occasions
126 mg/dL
CRITERIA USED TO DIAGNOSE
DIABETES : Two-hour postprandial glucose greater than __________ (7.8 mmol/L).
140 mg/dL
CRITERIA USED TO DIAGNOSE
DIABETES: Symptoms of hyperglycemia which include
polyuria (increased urine) , polyphagia (extreme hunger), polydipsia (extreme thirst)
CRITERIA USED TO DIAGNOSE
DIABETES: A two-hour postload glucose of _______________ in an OGTT.
200 mg/dL or greater than
CRITERIA USED TO DIAGNOSE
DIABETES : HbA1C of _________ or equal to 6.5%
greater than or equal to 6.5%
CRITERIA USED TO DIAGNOSE
DIABETES
FBS is greater than (126mg/dl)
2 hour postprandial is greater than (140mg/dl)
Symptoms of hyperglycemia
2 hour postload glucose 200mg/dl
HbA1C is greater than or equal 6.5%
Monitoring Test for Diabetes
Mellitus
Glycosylated hemoglobin
Fructosamine
Determined for DM once in 3 months
Glycosylated hemoglobin
ideal HbA1C valu
<7%
Factors affecting HBA1c
• Average glucose concentration
• RBC life span
Hemoglobinopathies, increased red
cell turnover
pregnancy
recent blood loss
transfusion
erythropoietin
therapy/hemolysis
Laboratory Testing of HbA1c: Specimen requirement
Ethylenediaminetetraacetid acid whole blood samples (hemolysate)
2 Categories of HbA1c
Charge difference
Structural characteristics of glycogroups on hemoglobin
Categories under Charge differences
cation exchange chromatography, electrophoresis,
isoelectric focusing
preferred method for HbA1c
Affinity chromatography
HbA1c attaches to the ________ group of the resin and is selectively eluted
from the resin bed using a buffe
boronate group
HbA1c attaches to the boronate group of the_______ and is selectively eluted
from the resin bed using a buffe
resin
Point of care HbA1c
latex immunoagglutination inhibition methodology
Monitor test for DM Once in 3 weeks
Fructosamine
Affected by albumin levels or hypoalbuminemia
• Liver disease
• Malabsorption
• Burns
• Nephrotic syndrome
Glucometer aka
Point of care blood glucose meter
Glucometer factor
1.11 concentration
Glucometer reaction
Glucose oxidase/peroxidase chromogen reaction
Glucometer factor
1.11 concentration
Factors affecting accuracy and reproducibility: glucometer
User variability
Hematocrit → the presence of anemia (false increase); polycythemia (false
decrease)
Defective reagent strips and instrument malfunction
Other variables: altitude, temperature, humidity, hypotension, hypoxia, high
triglyceride concentrations
Ketones specimen
Fresh serum/urine
Ketones method or test used
Gerhardt’s test
Copper Reduction Methods
Folin wu method
Nelson-somogyi method
Neocupreine method
Benedict’s method/fehlings method
Method that uses PMA
Folin wu method
Accurate but labor intensive and difficult to automate
Nelson-somogyi method
Cu+ reduces AMA to molybdenum blue
Nelson-somogyi method
Cu + neocupreine → yellow to yellow orange
Neocupreine method
Inverse colorimetry method
Ferric reduction (hagedorn jensen)
Ferric reduction Yellow → colorless measured at
400nm
Most sensitive
method glucose
Dubowski method - o-toluidine method
Uses acetic
acid
Dubowski method
Dubowski method that is used but
carcinogenic
and poisonous
O-toluidine
Wavelengths used dubowski method
630nm
Method that very specific to a substrate
Enzymatic method
first enzymatic reaction used
Glucose oxidase method
H2O2 measurement:
Trinders method
Peroxidase method
O2 is measured by:
Clark electrode
Ortho-dianisidine method
Disadvantage of Glucose
Oxidase Reaction
Glucose oxidase can only measure beta glucose
2 types of glucose
Alpha glucose
Beta glucose
Type of glucose 35% cannot be oxidized
Alpha glucose
Type of glucose 65% the only type which
can be oxidized
Beta glucose
Generally accepted method for measuring glucose
Hexokinase method
Uses alkaline ferricyanide
reagent
Autoanalyzer method
Gave falsely high results because
several compounds in serum alse
were oxidized by ferricyanide
Ferricyanide method
Ferricyanide method wavelength
400 nm
Used in establishing correct insulin
amount for next dose
Dextrostics
Widely used as a method of
screening for hypoglycemia of the
newborn
Dextrostic
Employs a paper strip impregnated
with an enzyme-chromogen system
Dextrostic
