Clinical Chemistry : Lipids, Lipoproteins, And Other Cardiac Markers

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

360 nm

350 nm

340 nm

330 nm

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.

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.

2. Definitive diagnostic method for any and all lipoproteins:

Gas Chromatography - Mass Spectroscopy

Electrophoresis

Polyanion Precipitation

Ultracentrifugation

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.

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.

3. The only lipoproteinemia that exhibits normal levels of TAG is:

Type 1

Type 2a

Type 2b

None of the Above

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

Explanation

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

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

High-Density Lipoprotein

Low-Density Lipoprotein

Troponin I

Potassium

All values are important in assessing cardiac function, but what gives physicians the clearest prediction of possible artherosclerotic and cardiac risk is the Low-Density Lipoprotein. Troponin I and Potassium, among other cardiac markers, gives physicians the sign that cardiac damage is happening.

Explanation

All values are important in assessing cardiac function, but what gives physicians the clearest prediction of possible artherosclerotic and cardiac risk is the Low-Density Lipoprotein. Troponin I and Potassium, among other cardiac markers, gives physicians the sign that cardiac damage is happening.

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

Xanthelasma

Arcus Juvenilis

Acanthosis Nigricans

None of the Above

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.

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.

6. The assay for Lipoprotein (a) is:

Immunospectroscopy

Immunonephelometry

Immunoturbidimetry

Immunofluoroscopy

Immunonephelometry is for apolipoprotein measurement.

Explanation

Immunonephelometry is for apolipoprotein measurement.

7. 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

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.

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.

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

Extraction : Cholesterol is released from the lipoprotein, thus ensuring no protein interference.

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.

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.

9. 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

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.

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.

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

Troponin T

Troponin I

Troponin C

None of the Above

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.

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.

11. 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

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

Explanation

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

12. 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

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

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.

13. 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

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.)

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.)

14. This apolipoprotein is the cofactor for LCAT.

Apo A-IV

Apo A-III

Apo A-II

Apo A-I

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.

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.

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

Cardiovascular

Exocrine

Endocrine

A and C

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".

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".