Clinical Chemistry : Lipids, Lipoproteins, And Other Cardiac Markers

2.

This is the umbrella medical term for hardening (and narrowing) of the arteries which are caused by several factors, one of these being high blood pressure.

Atherosclerosis
Arteriosclerosis
All of the Above
None of the Above

Correct Answer

A. Arteriosclerosis

Explanation

Arteriosclerosis is often interchanged with atherosclerosis but there is a difference between the two.

Arteriosclerosis is an umbrella term (meaning, a general term) for any number of diseases which cause the artery walls to thicken and narrow. There are three types of arteriosclerosis which includes atherosclerosis (the others being Moenckeberg Medial Calcific Sclerosis and Arteriolosclerosis).

Atherosclerosis is the name given to the build up of fats inside the artery walls which causes these to narrow and eventually restrict blood flow.

The pathogenesis is explained as follows:

The narrower your arteries, the harder your heart has to work to pump blood through them. This further increases the pressure of the blood flow which causes your blood pressure to rise even more.

The danger here is if an artery narrows to the extent that it becomes blocked which then prevents blood from flowing through. The part of the body which is nourished by this blood flow (and receives oxygen and vital nutrients) then dies which can have serious consequences.

If this happens near the brain then a stroke occurs.

If it happens near the heart then a heart attack occurs.

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1

3.

LDL can be computed by what equation?

[ TC - HDL - ( TAG / 5 ) ]
[ TC - HDL - ( 0.20 x TAG ) ]
All of the Above
None of the Above

Correct Answer

A. All of the Above

Explanation

Both equations are otherwise known are the Friedewald Formula. Both yield the same results, because 0.20 = 1/5.

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4.

Choose the incorrect non-enzymatic measurement step for cholesterol : description pair.

Colorimetry : The absorbance of the colored product (red for the Leibermann-Burchardt Reaction and green for the Salkowski Reaction) is read at 410 nm.
Extraction : Cholesterol is released from the lipoprotein, thus ensuring no protein interference.
Saponification : KOH hydrolyzes cholesteryl esters to free cholesterol, thus removing possible colorimetric interference due to the former, because only the latter is to be measured for cholesterol.
Precipitation : Digitonin is used to ensure no interference from other substances capable of absorbing light at 410 nm, such as bilirubin and hemoglobin.

Correct Answer

A. Colorimetry : The absorbance of the colored product (red for the Leibermann-Burchardt Reaction and green for the Salkowski Reaction) is read at 410 nm.

Explanation

The colored product for the LB Reaction is green, whereas that for the Salkowski Reaction (also known as the Zak Reaction) is red.

On an additional note for non-enzymatic cholesterol measurement:

One-Step Method
/ Colorimetry

Pearson-Stern-MacGavack Method
Zlatkis-Zak-Boyle Method
Ferro-Ham Method
Wybenga Method

Two-Step Method
/ Colorimetry + Extraction

Carr-Drekter Method (extraction is done by Zeolite)
Bloors Method (extraction is done by the Bloors Reagent / 3:1 Ethanol-Ether)

Three-Step Method
/ Colorimetry + Extraction + Saponification

Abell-Kendall Method (former CDC reference method)

Four-Step Method
/ Colorimetry + Extraction + Saponification + Precipitation

Schoenheimer-Sperry and Parekh-Jung Method (former CDC reference method)
Sperry-Webb Method

Take special note that the sequence for all four reactions will always start with the additional step (if there is any) and will always end with colorimetry (D U H). Therefore:
One-Step : Colorimetry
Two-Step : Extraction --> Colorimetry
Three-Step : Saponification --> Extraction --> Colorimetry
Four-Step : Precipitation --> Saponification --> Extraction --> Colorimetry

The methods of choice nowadays are nevertheless the enzymatic methods:

The Cholesterol Oxidase Method is the most commonly used method for cholesterol in laboratories. The chromogen measured is a quinoneimine dye.

The Modified Abell-Kendall / Abell-Levy-Brodie Method is considered the current CDC Reference Method. This employs the typical three-step method but neither the Bloors nor Zeolite Reagent is used, and it is rather hexane. The color reagent utilized is the Liebermann-Burchardt, thus resulting in a green chromogen measured with an absorbance of 410 nm.

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5.

This apolipoprotein is the cofactor for LCAT.

Apo A-IV
Apo A-III
Apo A-II
Apo A-I

Correct Answer

A. Apo A-IV

Explanation

Apo A-IV is the correct answer because it is known to be the cofactor for LCAT (lecithin-cholesterol acyltransferase). LCAT is an enzyme involved in the metabolism of lipoproteins, specifically in the esterification of cholesterol. Apo A-IV helps activate LCAT, allowing it to carry out its function effectively. Apo A-II, Apo A-I, and Apo A-III are other apolipoproteins but they do not serve as cofactors for LCAT.

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6.

The only lipoproteinemia that exhibits normal levels of TAG is:

Type 1
Type 2a
Type 2b
None of the Above

Correct Answer

A. Type 2a

Explanation

Both Type 1 and 2b, and other lipoproteinemias (Types 3, 4, and 5) exhibit high triglyceride levels.

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7.

Which of these is not a cutaneous marker for coronary artery disease?

Xanthelasma
Arcus Juvenilis
Acanthosis Nigricans
None of the Above

Correct Answer

A. None of the Above

Explanation

Xanthelasmas are yellow plaques that occur most commonly near the inner canthus (corner) of the eyelid, more often on the upper lid than the lower lid.

Arcus Juvenilis is a lipid-rich corneal arcus and a predominantly extracellular deposit that forms at the corneoscleral limbus.

Acanthosis nigricans is a skin disorder characterized by darkening (hyperpigmentation) and thickening (hyperkeratosis) of the skin, occurring mainly in the folds of the skin, back of the neck, the axilla and/or groin.

All of these, among others, are cutaneous markers for Coronary Artery Disease.

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8.

Acanthocytes are known for being a hematological sign of the following except:

Basser-Kornzweig Syndrome
Abetalipoproteinemia
Mutations of the XK gene
None of the Above

Correct Answer

A. None of the Above

Explanation

Basser-Kornzweig Syndrome are the same thing.

XK gene mutation is the disorder of McLeod Syndrome, and is characterized by the presence of acanthocytes, as well.

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9.

Definitive diagnostic method for any and all lipoproteins:

Gas Chromatography - Mass Spectroscopy
Electrophoresis
Polyanion Precipitation
Ultracentrifugation

Correct Answer

A. Electrophoresis

Explanation

This also aids in the identification of rare familial disorders such as Types I, III, and V Hyperlipidemia.

GC-MS specifically measures cholesterol.

Polyanion Precipitation is most commonly and reasonably specific for HDL.

Ultracentrifugation is for estimative fractionation of lipoprotein classes.

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10.

In the Three-Step Procedure (Ultracentrifugation + Precipitation + Abell-Kendall determination of supernatant cholesterol) for direct HDL measurement, what is used as the precipitant?

Heparin-Magnesium
Heparin-Manganese
Heparan-Sulfate
Heparan-Dihydrate

Correct Answer

A. Heparin-Manganese

Explanation

The function of the precipitant in this assay is to remove LDL.

The function of ultracentrifugation is to remove VLDL.

Therefore, only HDL will be detected.

(Chylomicrons have a short span in the bloodstream, and is extinguished after the hours desired for lipid profile fasting.)

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11.

Products for all enzymatic methods of triglycerides have an absorbance measured at:

360 nm
350 nm
340 nm
330 nm

Correct Answer

A. 340 nm

Explanation

The correct answer is 340 nm because the question states that products for all enzymatic methods of triglycerides have an absorbance measured at this wavelength. This suggests that 340 nm is the specific wavelength at which the enzymatic methods used for measuring triglycerides produce a detectable change in absorbance, indicating the presence or concentration of triglycerides.

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12.

The assay for Lipoprotein (a) is:

Immunospectroscopy
Immunonephelometry
Immunoturbidimetry
Immunofluoroscopy

Correct Answer

A. Immunoturbidimetry

Explanation

Immunonephelometry is for apolipoprotein measurement.

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13.

What are not the troponin forms released following cardiac myofibril necrosis?

Troponin T
Troponin I
Troponin C
None of the Above

Correct Answer

A. None of the Above

Explanation

These are all troponin subunits. Troponin C binds calcium, Troponin I inhibits troponin T, which is the tropomyosin-binding component. These, together with actin, are the contractile proteins of the cardiac myofibril.

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14.

The B-type Natriuretic Peptide proves what function of the heart?

Cardiovascular
Exocrine
Endocrine
A and C

Correct Answer

A. Endocrine

Explanation

B-type Natriuretic Peptide is a hormone secreted by the heart in response to increased pressure and volume in the cardiac chambers. It acts as a vasodilator and promotes diuresis to regulate blood pressure and fluid balance. This hormone is released into the bloodstream, affecting distant organs and tissues, which indicates an endocrine function of the heart. Therefore, the correct answer is "Endocrine".

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15.

What is the test that new-generation doctors request in tandem with LDL-C to determine risk for cardiac dysfunction?

Serum Amyloid Protein A
C-Reactive Protein
High-Sensitivity C-Reactive Protein
B and C

Correct Answer

A. High-Sensitivity C-Reactive Protein

Explanation

Concentrations of CRP (as detected by hs-CRP) below those seen in infection but nevertheless above healthy values can be a marker of atherosclerosis.

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Clinical Chemistry : Lipids, Lipoproteins, And Other Cardiac Markers

This analyte is currently considered the most important value in assessing cardiac risk and directing therapy.

Quiz Preview

This is the umbrella medical term for hardening (and narrowing) of the arteries which are caused by several factors, one of these being high blood pressure.

LDL can be computed by what equation?

Choose the incorrect non-enzymatic measurement step for cholesterol : description pair.

This apolipoprotein is the cofactor for LCAT.

The only lipoproteinemia that exhibits normal levels of TAG is:

Which of these is not a cutaneous marker for coronary artery disease?

Acanthocytes are known for being a hematological sign of the following except:

Definitive diagnostic method for any and all lipoproteins:

In the Three-Step Procedure (Ultracentrifugation + Precipitation + Abell-Kendall determination of supernatant cholesterol) for direct HDL measurement, what is used as the precipitant?

Products for all enzymatic methods of triglycerides have an absorbance measured at:

The assay for Lipoprotein (a) is:

What are not the troponin forms released following cardiac myofibril necrosis?

The B-type Natriuretic Peptide proves what function of the heart?

What is the test that new-generation doctors request in tandem with LDL-C to determine risk for cardiac dysfunction?