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Clin Chem > Lipid & Lipoprotein Measurement > Flashcards

Lipid & Lipoprotein Measurement Flashcards

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1
Q

Enumerate the biological variations that can affect lipid and lipoprotein levels

A

Age
Sex
Seasonal
Dietary intake
Medications
Medical disorders
Lifestyle and other biological variation

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2
Q

The higher the age, the ____.

A

higher the cholesterol

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3
Q

Women have ___ cholesterol levels than men.

A

lower

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4
Q

Cholesterol levels are ___ in the winter.

A

slightly higher

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5
Q

A person should be on their usual diet for __ weeks.

A

2

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6
Q

Daily intake of fat will ___ cholesterol level.

A

increase

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7
Q

In terms of acute illnesses, lipoprotein measurement should be made no sooner than ____ after any form of trauma or acute bacterial/viral infection, and ____ after childbirth.

A

8 weeks
3-4 months

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8
Q

True or false: Total cholesterol, HDL, LDL, and TAG can be measured in fasting patients only.

A

False

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9
Q

These can be measured in non-fasting individuals.

A

Total cholesterol
High-density lipoprotein

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10
Q

Requires fasting individuals

A

Triglycerides
Low-density lipoprotein

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11
Q

The ideal time that patients should fast before venipuncture

A

12 hours

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12
Q

Chylomicrons can markedly ___ the plasma triglyceride concentration.

A

increase

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13
Q

Chylomicrons are almost completely cleared within how many hours?

A

6-9 hours

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14
Q

The presence of chylomicrons after a ___ hour fast is considered ___.

A

12-hour
abnormal

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15
Q

What does NCEP mean?

A

National Cholesterol Education Program

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16
Q

Some LPP physiologically __ after meals due to __ changes.

A

decline/decrease
CETP-mediated compositional changes (Cholesteryl ester transfer protein)

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17
Q

When do CETP-mediated compositional changes occur?

A

When chylomicrons are catabolized

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18
Q

The NCEP Adult Treatment Panel III (ATP III) has recommended that patients fast for at least ___ before blood specimens are taken for lipid and lipoprotein analysis.

A

9 hours

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19
Q

When a standing patient reclines, concentrations of __, ___, and ___ decrease as much as ___.

A

Total cholesterol, Low-density lipoprotein, High-density lipoprotein
10%

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20
Q

Position of the patient must be standardized for venipuncture, preferably to the ___.

A

sitting position

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21
Q

When a standing patient reclines, ___ transfers to the ___ and dilutes non-diffusible plasma constituents.

A

extravascular water
vascular system

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22
Q

The NCEP guidelines recommend that patients be seated for ___ before sampling to prevent ___.

A

5 minutes
hemoconcentration

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23
Q

Hemoconcentration increase cholesterol by ___.

A

10-15%

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24
Q

Prolonged venous occlusion can lead to ___ and cholesterol increases ____.

A

hemoconcentration
10-15%

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25
Q

Plasma is preferred when the lipoproteins are measured by ___ and ___.

A

ultracentrifugation
electrophoresis

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26
Q

Why is plasma preferred?

A

Samples can be cooled to 4°C and retire the changes occurring at room temperature.

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27
Q

True or false: Plasma should remain in contact with the cells overnight.

A

False (should not)

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28
Q

___ occurs less frequently using serum

A

Protein aggregation

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29
Q

True or false: Protein aggregation can still occur in plasma, even in the presence of an anticoagulant.

A

True

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30
Q

What anticoagulant does a blue top tube contain?

A

Citrate

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31
Q

What anticoagulant does a green top tube contain?

A

Heparin

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32
Q

What anticoagulant does a purple top tube contain?

A

Ethylenediamine-tetraacetic acid (EDTA)

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33
Q

___ exert rather large osmotic effects that result in ___ plasma lipid and lipoprotein concentrations.

A

Citrate
falsely low

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34
Q

_____, because of its relatively high molecular weight, has little effect on plasma volume but can alter the electrophoretic mobilities of the lipoproteins.

A

Heparin

35
Q

What is the preferred anticoagulant?

A

EDTA

36
Q

True or false: Ethylenediaminetetraacetic acid (EDTA) is the preferred anticoagulant even though cholesterol and triglyceride concentrations in EDTA plasma are about 5% lower than in serum.

A

False (3%)

37
Q

EDTA retards certain kinds of ___ and ___ occurring in your lipoprotein during storage.

A

oxidative
enzymatic alterations

38
Q

These can be analyzed with frozen samples

A

Total protein, Triglycerides, High-density lipoprotein, Apolipoproteins

39
Q

What are the storage requirements for a sample?

A

Long-term (>2 months): −70°C or lower
Short-term (1-2 months): −20°C

40
Q

Why are frozen samples not appropriate for ultracentrifugal analysis?

A

Triglyceride-rich lipoprotein does not withstand freezing

41
Q

What are the most common chemical methods for your cholesterol?

A

Liebermann-Burchard Test
Salkowski Test
Abell-Kendall Test

42
Q

Two laboratory methods (cholesterol)

A

Chemical methods
Enzymatic methods

43
Q

Positive indicator of Liebermann-Burchard’s test

A

Green

44
Q

In Liebermann-Burchard’s test, the dry extract was dissolved in ___ then ___ was added along the sides of the test tube.

A

acetic anhydride
concentrated sulfuric acid

45
Q

Positive indicator of Salkowski’s reaction

A

Red

46
Q

A positive result in Liebermann-Burchard’s test indicates what?

A

presence of steroids

47
Q

A positive result in Salkowski’s reaction indicates what?

A

presence of steroids

48
Q

In Salkowski’s reaction, the dry extract was shaken with ___, forming ___, then ___ was added slowly by the sides of the test tube.

A

chloroform
chloroform layer
sulfuric acid

49
Q

In the Abell-Kendall method, ___ are hydrolyzed with ___ to unesterified form.

A

cholesteryl esters
alcoholic potassium hydroxide (KOH)

50
Q

In the Abell-Kendall method, unesterified cholesterol is extracted with ___ and measured with the ___.

A

petroleum ether
Liebermann-Burchard reagent

51
Q

The Liebermann-Burchard reagent is composed of?

A

Sulfuric acid
Acetic acid
Acetic anhydride

52
Q

Positive indicator of the Abell-Kendall method

A

Bluish-green

53
Q

The enzymatic method will use a ___ sample volume.

A

smaller

54
Q

It is rapid and precise compared to the other method.

A

enzymatic method

55
Q

Cholesteryl ester with the combination of water will be acted by the ___ forming ___ and ___.

A

cholesteryl esterase
cholesterol; free fatty acid

56
Q

Cholesterol, with the action of added oxygen, will be acted by the ___ forming ___ and ___.

A

cholesterol oxidase
cholest-4-en-3-one; hydrogen peroxide

57
Q

Hydrogen peroxide, one of the reaction products, is measured by ___ that will now form a colored dye which is the ___.

A

peroxidase-catalyzed reaction
Quinoneimine

58
Q

What device is used to quantitate the cholesterol level?

A

Spectrophotometer

59
Q

What are the interfering substances that react in the chemical methods?

A

plant sterol
ascorbic acid
bilirubin
sample turbidity
high levels of hemoglobin

60
Q

Ascorbic acid interferes by consuming what?

A

hydrogen peroxide

61
Q

High levels of ascorbic acid or bilirubin level lead to a ___ of the result.

A

false decrease

62
Q

The hydrogen peroxide produced in the cholesterol oxidase reaction can be oxidatively coupled to two chromogenic substrates by catalysis with a peroxidase, most commonly ___.

A

horseradish peroxidase

63
Q

Chromogens

A

phenol
4-aminoantipyrine

64
Q

The quinoneimine dye can be read photometrically at?

A

500nm

65
Q

True or false: Enzymatic methods require a preliminary extraction step.

A

False (NO preliminary extraction step)

66
Q

One chemical method still used is the ___.

A

CDC reference method for triglycerides

67
Q

The CDC-reference method uses a ___ extraction (of triglycerides) procedure followed by ___ to isolate ___.

A

chloroform
silicic acid chromatography

68
Q

Glycerol is released by ___.

A

Saponification

69
Q

Positive indicator of the CDC-reference method

A

Pink

70
Q

This limits interfering substances.

A

CDC-reference method

71
Q

NADH formation can be measured spectrophotometrically at __.

A

340nm

72
Q

The disappearance of NADH is measured at ___.

A

340 nm

73
Q

This is separated by chemical precipitation.

A

HDL Cholesterol

74
Q

What are the precipitating agents used in HDL-cholesterol measurement?

A

Earliest – heparin in combination with manganese to precipitate apo B-containing LPP (lipoprotein)
Alternative – sodium phosphotungstate with magnesium
More specific – Dextran sulfate with magnesium

75
Q

Interfering factor (HDL-Cholesterol measurement)

A

elevated triglyceride levels

76
Q

What is/are the gold standard/reference method in HDL-Cholesterol measurement?

A

Ultracentrifugation – to remove VLDL
Heparin Manganese Precipitation – to remove LDL
Analysis of supernatant cholesterol by the Abell-Kendall Assay

77
Q

What is/are the reference method for LDL-cholesterol measurement?

A

Beta-Quantification
Electrophoretic migration
Ultracentrifugation + Chemical precipitation

78
Q

LDL-Cholesterol Method routine method

A

Friedewald Calculation

79
Q

Reference range for Total Cholesterol

A

140-200 mg/dL (3.6-5.2 mmol/L)

80
Q

Reference range for high-density lipoprotein cholesterol

A

40-75 mg/dL (1.0-2.0 mmol/L)

81
Q

Reference range for low-density lipoprotein cholesterol

A

50-130 mg/dL (1.3-3.4 mmol/L)

82
Q

Reference range for triglycerides

A

60-150 mg/dL (0.7-1.7 mmol/L)

83
Q

What is the equation of Friedewald?

A

LDL = TC - HDL - (TAG/2.175) (mmol/L)
LDL = TC - HDL - (TAG/5) (mg/dL)

Clin Chem (1 decks)

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