B - Chapter VI: Carbohydrates Flashcards
1
Q
use (?)
A
serum, plasma or whole blood
2
Q
whole blood values (?) lower than serum or plasma
A
10 - 15%
3
Q
erum or plasma should be refrigerated and separated from the cells (?) to prevent substantial loss thru glycolysis
A
within1 hour
4
Q
separated unhemolyzed serum at rm temperature is stable for
A
8 hr; ref temperature for 48 - 72 hr
5
Q
preferred additive :
A
sodium fluoride (gray top)
6
Q
: approximately 8 - 10 hr fast (not >16 hr)
A
FBS
7
Q
: immediate processing to prevent bacterial utilization of glucose
A
CSF glucose
8
Q
: only for monitoring of diabetics and not for diagnosis
A
urine sugar
9
Q
Chemical methods − done in an
A
alkaline medium
10
Q
− glucose + boiling water —-> (?) (enol anion form) : reduce metallic ions
A
eneidol
11
Q
Alkaline Copper reduction Tests
A
Folin-Wu
Nelson-Somogyi
Neocuproine
12
Q
total reducing substances (true reducing substances and saccharoids) measured
A
Folin-Wu
13
Q
barium sulfate enables measurement of true reducing substances only
A
Nelson-Somogyi
14
Q
Campbell and King method
A
Neocuproine
15
Q
neocuproine (7,9- dimethyl-1,10-phenanthroline) —> cuprous-neocuproine complex (yellow-orange)
A
Neocuproine
16
Q
arsenomolybdic acid —> arsenomolybdenum blue
A
Nelson-Somogyi
17
Q
phosphomolybdic acid —> phosphomolybdenum blue
A
Nelson-Somogyi
18
Q
Alkaline Ferric reduction tests
A
- Johnson method
- Folin/ Prussian blue method
- Hagedorn-Jensen method
19
Q
− reverse colorimetric method
− more specific than copper reduction
A
Alkaline Ferric reduction
20
Q
− ferricyanide —> ferrocyanide
A
Alkaline Ferric reduction
21
Q
Condensation methods
A
(a) with aromatic amines
(b) with phenols
22
Q
Ortho-toluidine method by Dubowski (reference method)
A
Condensation methods with aromatic amines
23
Q
based on the ability of carbohydrates to form Schiff bases with aromatic amines
A
Condensation methods with aromatic amines
24
Q
glucose + ortho-toluidine —-> N-glycosylamine: Schiff base (green) 630 nm
A
Condensation methods with aromatic amines
25
Condensation methods with aromatic amines interfering substances:
galactose, mannose and aldopentose
26
glucose ---> water + hydroxymethylfurfural (HMF)
Condensation methods with phenols
27
HMF + anthrone ---> green colored compound
Condensation methods with phenols
28
Enzymatic methods
(a) Glucose Oxidase method
(b) Hexokinase method
(c) Glucose Dehydrogenase (GDH)
29
most specific enzyme reacting with only β-D-glucose
Glucose Oxidase method
30
glucose + O2 + H2O --- GOD ---> gluconic acid + H2O2
Glucose Oxidase method
31
H2O2 + reduced chromogen --- POD---> oxidized chromogen + H2O
Glucose Oxidase method
32
mutarotase : added to convert alpha to beta glucose
Glucose Oxidase method
33
Methods to quantify H2O2 :
1. Gochman and Schmitz
2. Trinder
34
3-methyl-2-benzathiazolinone hydrazone + N,N-dimethylaniline ---> indamine dye (590-66- nm)
Gochman and Schmitz
35
p-aminophenazone + phenol ----> purple product (quinoneimine)
Trinder
36
2,2-azine-di(3-ethyl bezothiazoline-(6)-sulfonic acid ---> colored chromogen
Miskieweis
37
- measures the amount of oxygen consumed in the glucose oxidase method
POLAROGRAPHIC OXYGEN ELECTRODE
38
POLAROGRAPHIC OXYGEN ELECTRODE
To prevent the formation of oxygen from H2O2 (by catalase present in some GOD preparations), it is removed by inclusion of two additional reactions:
❖ H2O2 + ethanol ----- catalase------ Acetaldehyde + H2O
❖ H2O2 + H+ + 2I- --- molybdate ---- I2 + 2H2O
39
- recommended for type 1 diabetics
Self-Monitoring of Blood Glucose: point of care device
40
- to maintain levels as close to normal as possible
Self-Monitoring of Blood Glucose: point of care device
41
- whole blood glucose testing using capillary blood as sample
Self-Monitoring of Blood Glucose: point of care device
42
- more accurate, less interferences than glucose oxidase methods (REFERENCE method)
Hexokinase method
43
- not affected by uric acid and ascorbic acid
Hexokinase method
44
- false decrease: hemolyzed sample and elevated bilirubin levels
Hexokinase method
45
- can also be used for urine, CSF and serous fluids
Hexokinase method
46
− glucose + ATP ---hexokinase ---> glu-6-phosphate + ADP
Hexokinase method
47
− glu-6-phosphate + NADP ---G-6-PD ---> NADPH + H + 6-phosphogluconate (340 nm)
Hexokinase method
48
Glucose + NAD ------ GDH ----- Gluconolactone + NADH + H+
Glucose Dehydrogenase (GDH)
49
Coenzyme I: NAD
Coenzyme II: NADP
Glucose Dehydrogenase (GDH)
50
− increased plasma glucose levels
HYPERGLYCEMIA
51
− caused by imbalance of hormones
HYPERGLYCEMIA
52
− normally : insulin is secreted : enhance entry of glucose into the liver, muscle and adipose and alters glucose metabolic pathways
HYPERGLYCEMIA
53
Laboratory Findings in Hyperglycemia
1. increased glucose in plasma and urine
2. increased urine specific gravity
3. increased serum and urine osmolality
4. ketonemia and ketonuria
5. decreased blood and urine pH (acidosis)
6. electrolyte imbalance
54
CLASSIFICATION of DIABETES MELLITUS:
1. Type 1 DM
2. Type 2 DM
3. Gestational diabetes mellitus (GDM)
4. Due to other causes:
- monogenic diabetes syndromes
- diseases of the exocrine pancreas
- drug- or chemical-induced diabetes
55
due to autoimmune β-cell destruction, usually leading to absolute insulin deficiency
Type 1 DM
56
due to a progressive loss of β-cell insulin secretion frequently on the background of insulin resistance
Type 2 DM
57
diabetes diagnosed in the 2nd or 3rd trimester of pregnancy that was not clearly overt diabetes prior to gestation
Gestational diabetes mellitus (GDM)
58
e.g. neonatal diabetes & maturity-onset diabetes of the young [MODY]
monogenic diabetes syndromes
59
e.g. cystic fibrosis
exocrine pancreas
60
e.g. with glucocorticoid use
drug- or chemical-induced diabetes
61
Fasting is defined as no caloric intake for at least 8 hours
FPG ≥ 126 mg/dL (7.0 mmol/L)
62
The test should be performed as described by the WHO, using a glucose load containing the equivalent of 75 g anhydrous glucose dissolved in water.
2-H PG ≥ 200 mg/dL (11.1 mmol/L) during an OGTT.
63
The test should be performed in a laboratory using a method that is NGSP certified and standardized to the DCCT assay
A1C ≥ 6.5% (48 mmol/mol).
64
In a patient with classic symptom of hyperglycemia or hyperglycemic crisis
random plasma glucose ≥200 mg/dL (11.1 mmol/L)
65
Frequency 5-10%
66
Frequency 90-95%
67
Age of onset
Any; most common in children and young adults
68
Age of onset
More common in advancing age; can occur in children and adolescents
69
Risk factors
Genetic (HLA-DR/DQ on chr 6)
Autoimmune
Environmental
70
Risk factors
Genetic
Obesity (BMI)
Sedentary lifestyle
Race/ethnicity
71
Pathogenesis:
Destruction of beta cells usually autoimmune
72
Pathogenesis:
No autoimmunity
Insulin resistance
Progressive insulin deficiency
73
C peptide:
Very low or undetectable
74
C peptide:
Detectable
75
Pre-diabetes:
Autoantibodies (GAD65,ICA512,IAA) may be present
GAD glutamic acid decarboxylase
ICA islet cell antigen
IAA insulin autoantibodies
76
Pre-diabetes:
Autoantibodies absent (testing not indicated)
77
Medication therapy:
Insulin
78
Medication therapy:
Oral hypoglycemic agents
79
Therapy to prevent or delay onset of diabetes:
None known
80
Therapy to prevent or delay onset of diabetes:
Lifestyle change Oral hypoglycemic agents (metformin and acarbose)
81
TOLERANCE TESTS PATIENT PREPARATION:
1. [?] of unrestricted diet
2. Avoid [?] that will interfere with the test
3. No [?]
4. No alcohol / no [?]
5. (?) fast
3 days
medications
beverages
cigarettes
Overnight 8 – 14 hour
82
2-hour Postprandial Test Dose:
a gram / kg body wt.
83
2-hour Postprandial Test Normal: peak value in [?]; back to normal in [?]
30 mins. (~150 mgs%)
2 hrs
84
5-hour Postprandial Test Dose:
75 grams (WHO 1985)
85
5-hour Postprandial Test Normal: back to normal in [?]
5 hours
86
5-hour Postprandial Test
Done only if value of 2-hr PPT is [?]
>140 – 160 mgs%
87
Indications:
Poor absorption of ingested CHO
History of GIT surgery
Intravenous Glucose Tolerance Test (IVGTT)
88
Intravenous Glucose Tolerance Test (IVGTT) Dose: [?] ([?] solution given intravenously)
0.5g/kg
25 g/dL
89
Insulin tolerance test Dose:
0.1 unit / kg
90
Insulin tolerance test Normal:
In [?], [?] decrease in FBS level; back to normal on [?].
30 mins
50%
2nd hr
91
❖ Delayed decrease in BGL
Insulin Resistance
92
❖ DM, hyperadrenalism, Acromegaly
Insulin Resistance
93
❖ Normal fall of BGL but delay in regaining normal value
Hypoglycemic Unresponsiveness
94
❖ Addison’s disease, hypofunction of anterior PG, hyperinsulinism, Von Gierke’s disease
Hypoglycemic Unresponsiveness
95
Stimulates pancreas to produce insulin
Orinase or Tolbutamide
96
Evaluates hypoglycemia caused by insulinoma
Orinase or Tolbutamide
97
Tolbutamide Tolerance Test
In [?], [?] decrease in FBS level; back to normal on [?].
30 mins
50%
2nd hr
98
Serves as an index of the quantity & availability of glycogen
Epinephrine tolerance test
99
Interpretation: Peak value after 30 mins.; normal within 2 hours
Epinephrine tolerance test
100
35 – 45 mgs% increase in conc. between 45 – 60 mins.
Epinephrine tolerance test
101
Detects the presence of mucosal lactase
Lactose tolerance test
102
Causes of Lactose Intolerance:
Deficiency of lactase
Inhibition to lactase activity (e.g. intestinal disorders)
103
− Defined as any degree of glucose intolerance that was first recognized during pregnancy, regardless of whether the condition may have predated the pregnancy or persisted after the pregnancy
GESTATIONAL DIABETES MELLITUS
104
- results from an imbalance between glucose utilization and production
HYPOGLYCEMIA
105
- observable symptoms appear at about 50-55 mg/Dl
HYPOGLYCEMIA
106
- triggered by the ANS
Neurogenic
107
- tremulousness, palpitations, anxiety
Neurogenic
108
- diaphoresis, hunger, paresthesias
Neurogenic
109
- CNS hypoglycemia
Neuroglycopenic
110
- dizziness, tingling, difficulty concentrating, blurred vision
Neuroglycopenic
111
- confusion, behavioral changes, seizure, coma
Neuroglycopenic
112
historically : postabsorptive (?) and postprandial (?) hypoglycemia
(fasting)
(reactive)
113
Measure glycosylated hemoglobin (HbA1c) every (?)
3-6 months
114
(?) + (?) = ketoamine
glucose
amino group of hemoglobin
115
rate of formation is directly proportional to
plasma glucose concentration
116
provides an index of average BGL over the past 2-4 months
Measure glycosylated hemoglobin (HbA1c) every 3-6 months
117
Values for total HbA1 & HbA1c have a high degree of correlation
EDTA whole blood sample
118
TESTS FOR MONITORING DIABETIC PATIENTS
A. Measure glycosylated hemoglobin (HbA1c)
B. Microalbuminuria
C. C peptide
119
METHODS for MEASUREMENT of Hemoglobin A1C:
1. ION-EXCHANGE CHROMATOGRAPHY
2. HPLC
3. COLORIMETRY
4. RADIOIMMUNOASSAY (RIA)
5. ELECTROPHORESIS
6. ISOELECTRIC FOCUSING
7. AFFINITY CHROMATOGRAPHY
120
Cation-exchange resin or carboxymethyl cellulose resin
ION-EXCHANGE CHROMATOGRAPHY
121
Reference method
HPLC
122
Hb A1c --- acid --- 5-HMF
COLORIMETRY
123
Antibodies against Hb A1c (sheep antiserum)
RADIOIMMUNOASSAY (RIA)
124
Citrate agar electrophoresis (pH 6.0-6.2)
ELECTROPHORESIS
125
Good resolution of Hb A & Hb A1
ELECTROPHORESIS
126
Scanned on high-resolution microdensitometer
ISOELECTRIC FOCUSING
127
Hb A1c is adequately resolved from HbA1a, A1b, S and F
ISOELECTRIC FOCUSING
128
Use of affinity gel columns
AFFINITY CHROMATOGRAPHY
129
- useful to assist in diagnosis at an early stage and before the development of proteinuria (> 0.5g/day)
Microalbuminuria
130
- reflects pancreatic secretion of insulin
C peptide
131
- proinsulin cleaved to give C peptide and insulin
C peptide
132
- reflects endogenous insulin production if patient is taking insulin
C peptide
133
: produced by the liver thru the metabolism of fatty acids to provide a ready energy source from stored lipids at times of low carbohydrate availability
ketone bodies
134
3 types of ketone bodies :
acetone (2%), acetoacetic acid (20%) and 3-beta-hydroxybutyric acid (78%)
135
Ketone measurement diseases
ketonemia and ketonuria
136
type 1 DM :
acute illness, stress, pregnancy, hyperglycemia of >300mg/dL or with signs of ketoacidosis
137
serious and potentially fatal hyperglycemic condition
DKA
138
nausea, vomiting, abdominal pain, electrolyte disturbances and severe dehydration
DKA
139
specimen considerations :
− fresh serum or urine − tightly stoppered and assayed ASAP
140
Ketone measurement lab methods :
a. Gerhardt's
b. acetoacetic acid + sodium nitroprusside ----> purple color
c. enzymatic method
141
a. Gerhardt's : acetoacetic acid + ferric chloride ---> red color
142
b. acetoacetic acid + sodium nitroprusside ---->
purple color
143
acetoacetic acid + NADH + H ---β-HBDH---> NAD + beta-hydroxybutyric acid
c. enzymatic method
