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CC 1 > 5.1 LIPIDS LABORATORY METHODS AND CLINICAL SIGNIFICANCE > Flashcards

5.1 LIPIDS LABORATORY METHODS AND CLINICAL SIGNIFICANCE Flashcards

1
Q

What is the preferred sample for laboratory tests?

A

Serum collected in SST

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2
Q

Why is serum preferred over plasma for certain measurements?

A

Serum does not contain fibrinogen, which can interfere with tests

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3
Q

What anticoagulant is preferred for lipoprotein assays?

A

Ethylenediaminetetraacetic acid (EDTA)

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4
Q

What types of samples are used for measuring total cholesterol (TC), triglycerides (TAG), HDL-C, and LDL-C?

A

Plasma or serum

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5
Q

How long should a patient fast before lipid profile testing?

A

12-14 hours

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6
Q

How long does it take for chylomicrons to clear from circulation?

A

6-9 hours

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7
Q

What effect does posture have on lipid concentration measurements?

A

Recumbence can decrease concentrations by as much as 10%

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8
Q

What is the recommendation before sampling to prevent hemoconcentration?

A

Patients must be seated for 5 minutes

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9
Q

What is the recommended temperature for long-term storage of serum/plasma?

A

-70 degrees Celsius or lower

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10
Q

What is the recommended temperature for short-term storage?

A

-20 degrees Celsius

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11
Q

What is the principle behind chemical methods for cholesterol measurement?

A

Dehydration and oxidation of cholesterol to form a colored compound

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12
Q

What is the expected color change in the Liebermann-Burchardt reaction?

A

Green

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13
Q

What reaction is involved in the Salkowski method?

A

Cholestadienyl Disulfonic Acid, expected color: Red

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14
Q

What is the CDC reference method for cholesterol measurement?

A

Gas Chromatography Mass Spectrometry (GC-MS)

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15
Q

What method uses hexane extraction after hydrolysis for cholesterol measurement

A

Abell, Levy, and Brodie Method

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16
Q

What is the CDC reference method for triglyceride measurement?

A

Saponification with alcoholic KOH, extraction with chloroform, treatment with silicic acid

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17
Q

What is the expected end product color for triglyceride measurement

A

Pink Chromophore

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18
Q

What color does the “Van Handel and Zilversmith” method produce?

A

Blue color compound

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19
Q

What is the fluorescent compound used in the Hantzsch Condensation method?

A

Diacetyl Lutidine Compound

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20
Q

What method is used for spectrophotometry in the Glycerol Kinase method?

A

Enzymatic method involving lipase and glycerol kinase.

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21
Q

What is the reference method for quantifying lipoproteins?

A

Ultracentrifugation methods

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22
Q

What components are lipoproteins quantified based on?

A

CHON (protein) and TAG (triglyceride) contents.

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23
Q

What is the most commonly used support medium for electrophoresis?

A

Agarose gel

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24
Q

How does HDL migrate during electrophoresis?

A

HDL migrates with the alpha1-globulins.

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25
Q

What does the presence of VLDL in the beta region indicate?

A

It is an abnormal lipoprotein associated with Type 3 Familial Hypercholesterolemia.

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26
Q

What staining dye is commonly used to visualize lipoprotein electrophoretograms?

A

Oil Red O.

27
Q

What do polyanion precipitation methods use to react with positive lipoproteins?

A

Polyanions such as heparin sulfate, dextran sulfate, or phosphotungstate.

28
Q

What HDL-C level indicates a high risk for coronary heart disease (CHD)?

A

HDL-C < 35 mg/dL

29
Q

What HDL-C level is considered protective?

A

HDL-C > 60 mg/dL.

30
Q

What is a characteristic of homogenous assays?

A

They are fully automated two-reagent procedures

31
Q

What formula is used in the Friedewald method to calculate LDL-C?

A

TC = HDL-C + (TAG/2.175) or (TAG/5)

32
Q

What is the De Long Method used for?

A

Used if the triglyceride value is ≥ 400 mg/dL.

33
Q

What density is used in ultracentrifugation to float and remove VLDL and chylomicrons?

A

1.006 kg/L.

34
Q

How does the Homogenous Direct LDL-C method measure LDL directly?

A

It uses two reagents: one to remove non-LDL lipoproteins and one to release cholesterol from LDL.

35
Q

What is the purpose of the Standing Plasma Test for chylomicrons?

A

To observe a floating “creamy” layer indicating the presence of chylomicrons

36
Q

How are apolipoproteins typically measured?

A

By immunoassay or immunophelometry.

37
Q

What are apolipoproteins used as in the immunoassay?

A

Antigens in antigen-antibody complexes.

38
Q

What common cardiovascular disorders are associated with the development of atherosclerosis?

A

Myocardial infarction, cerebrovascular disease, and peripheral vascular disease

39
Q

Increased lipid concentration

A

hyperlipidemia

40
Q

Occurs when a portion of the heart stops beating due to insufficient oxygen supply because an artery is blocked by atherosclerosis.

A

Myocardial infarction

41
Q

Caused by dislodged cholesterol plaque leading to cerebral embolism (stroke)

A

Cerebrovascular disease

42
Q

When dislodged plaque travels to other areas of the body.

A

Peripheral vascular disease

43
Q

Decreased lipid concentration

A

hypolipidemia

44
Q

likely caused by multifactorial reasons, not limited to family history

Represents about 85% of cases of hypercholesterolemia in the population

A

polygenic (nonfamilial) hypercholesterolemia

45
Q

What genetic defect causes familial hypercholesterolemia?

A

Defective or deficient LDL-receptor gene on chromosome 19.

46
Q

What is the expected LDL level in patients with familial hypercholesterolemia

A

High LDL levels

47
Q

A rare autosomal recessive disorder causing the accumulation of phytosterols in plasma due to genetic mutations

A

sitosterolemia

48
Q

are plant sterols that are typically not absorbed by the body and are excreted or degraded

A

Phytosterols

49
Q

What gene mutations are associated with sitosterolemia?

A

Mutations in the ABCG8 or ABCG5 gene on chromosome 2p21

50
Q

These genes are involved in the transport and absorption of sterols.

A

ABCG8 or ABCG5 gene on chromosome 2p21.

51
Q

Abnormal, thorny-shaped red blood cells found in abetalipoproteinemia

A

acanthocytes

52
Q

Their presence indicates a significant lipid metabolism disorder

A

acanthocytes

53
Q

What is the cause of abetalipoproteinemia

A

Defective Apo B synthesis due to deficiency of microsomal TAG transfer protein (MTP)

54
Q

VLDL, LDL, and chylomicrons are absent in plasma, leading to fat malabsorption and vitamin deficiencies.

A

abetalipoproteinemia

55
Q

What is hypobetalipoproteinemia caused by

A

Apo-B deficiency from a point mutation in Apo-B

56
Q

This results in decreased levels of LDL-C and total cholesterol

A

hypobetalipoproteinemia

57
Q

Very low levels of HDL due to a mutation in the ABCA1 gene on chromosome 9.

A

Tangier disease

58
Q

What accumulates in the body due to LCAT gene mutations in Tangier disease

A

Free cholesterol

59
Q

What syndrome results from LPL deficiency?

A

Classic type 1 chylomicronemia syndrome.

60
Q

What is the typical lab result for TAG in patients with LPL deficiency

A

TAG = 10,000 mg/dL or 113 mmol/L

61
Q

What is a characteristic of chylomicron retention disease

A

High levels of chylomicrons in circulation.

62
Q

What are common clinical findings in chylomicron retention disease

A

Hypocholesterolemia, chronic diarrhea, failure to thrive, and fat-soluble vitamin deficiency (particularly Vitamin E)

63
Q

What is the conversion factor for cholesterol from mg/dL to mmol/L

A

0.026

64
Q

What is the conversion factor for TAG from mg/dL to mmol/L

A

0.0113

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