5.1 LIPIDS LABORATORY METHODS AND CLINICAL SIGNIFICANCE Flashcards by 횐호 강

What is the preferred sample for laboratory tests?

Serum collected in SST

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Why is serum preferred over plasma for certain measurements?

Serum does not contain fibrinogen, which can interfere with tests

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What anticoagulant is preferred for lipoprotein assays?

Ethylenediaminetetraacetic acid (EDTA)

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

Plasma or serum

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How long should a patient fast before lipid profile testing?

12-14 hours

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

6-9 hours

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What effect does posture have on lipid concentration measurements?

Recumbence can decrease concentrations by as much as 10%

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What is the recommendation before sampling to prevent hemoconcentration?

Patients must be seated for 5 minutes

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

-70 degrees Celsius or lower

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What is the recommended temperature for short-term storage?

-20 degrees Celsius

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What is the principle behind chemical methods for cholesterol measurement?

Dehydration and oxidation of cholesterol to form a colored compound

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

Green

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What reaction is involved in the Salkowski method?

Cholestadienyl Disulfonic Acid, expected color: Red

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What is the CDC reference method for cholesterol measurement?

Gas Chromatography Mass Spectrometry (GC-MS)

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What method uses hexane extraction after hydrolysis for cholesterol measurement

Abell, Levy, and Brodie Method

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What is the CDC reference method for triglyceride measurement?

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

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What is the expected end product color for triglyceride measurement

Pink Chromophore

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

Blue color compound

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

Diacetyl Lutidine Compound

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

Enzymatic method involving lipase and glycerol kinase.

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What is the reference method for quantifying lipoproteins?

Ultracentrifugation methods

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What components are lipoproteins quantified based on?

CHON (protein) and TAG (triglyceride) contents.

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What is the most commonly used support medium for electrophoresis?

Agarose gel

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How does HDL migrate during electrophoresis?

HDL migrates with the alpha1-globulins.

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

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

What staining dye is commonly used to visualize lipoprotein electrophoretograms?

Oil Red O.

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

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

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

HDL-C < 35 mg/dL

What HDL-C level is considered protective?

HDL-C > 60 mg/dL.

What is a characteristic of homogenous assays?

They are fully automated two-reagent procedures

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

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

What is the De Long Method used for?

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

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

1.006 kg/L.

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

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

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

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

How are apolipoproteins typically measured?

By immunoassay or immunophelometry.

What are apolipoproteins used as in the immunoassay?

Antigens in antigen-antibody complexes.

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

Myocardial infarction, cerebrovascular disease, and peripheral vascular disease

Increased lipid concentration

hyperlipidemia

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

Myocardial infarction

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

Cerebrovascular disease

When dislodged plaque travels to other areas of the body.

Peripheral vascular disease

Decreased lipid concentration

hypolipidemia

likely caused by multifactorial reasons, not limited to family history Represents about 85% of cases of hypercholesterolemia in the population

polygenic (nonfamilial) hypercholesterolemia

What genetic defect causes familial hypercholesterolemia?

Defective or deficient LDL-receptor gene on chromosome 19.

What is the expected LDL level in patients with familial hypercholesterolemia

High LDL levels

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

sitosterolemia

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

Phytosterols

What gene mutations are associated with sitosterolemia?

Mutations in the ABCG8 or ABCG5 gene on chromosome 2p21

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

ABCG8 or ABCG5 gene on chromosome 2p21.

Abnormal, thorny-shaped red blood cells found in abetalipoproteinemia

acanthocytes

Their presence indicates a significant lipid metabolism disorder

acanthocytes

What is the cause of abetalipoproteinemia

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

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

abetalipoproteinemia

What is hypobetalipoproteinemia caused by

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

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

hypobetalipoproteinemia

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

Tangier disease

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

Free cholesterol

What syndrome results from LPL deficiency?

Classic type 1 chylomicronemia syndrome.

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

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

What is a characteristic of chylomicron retention disease

High levels of chylomicrons in circulation.

What are common clinical findings in chylomicron retention disease

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

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

0.026

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

0.0113