Chemistry Study Material: Section 7.2 - In-depth Exploration of Cardiovascular Disease II

What is the optimal level of HDL?

>60 mg/dL

What is the optimal level of LDL?

What is the optimal level of triglycerides?

What is the optimal level of total cholesterol (TC)?

Total cholesterol is most commonly measured with an enzymatic method, but the Gold Standard measurement for TC is ____________?

GC-MS

Which lipid tests make up the lipid panel set by the NCEP, and what is the recommended guideline for frequency of testing for adults?

Total cholesterol, HDL, LDL, Triglycerides

once every 5 years

What is considered a "low risk" for CHD, according to the ATP Treatment Guidelines?

0-1 risk factors and an LDL outside of the optimal range

What is considered a "moderate risk" for CHD, according to the ATP Treatment Guidelines?

2 or more risk factors, plus LDL and HDL outside optimal ranges

What is considered a "moderately high risk" for CHD, according to the ATP Treatment Guidelines?

2 or more risk factors, plus LDL, HDL, and triglyceride outside optimal ranges

What is considered a "high risk" for CHD, according to the ATP Treatment Guidelines?

presence of clinical atherosclerotic disease such as CHD, Carotid Artery Disease, Peripheral arterial disease or abdominal aortic aneurysm automatically confers high risk

What are the 3 enzymes involved in measuring total cholesterol?

cholesterol esterase, cholesterol oxidase, peroxidase

What are some interferences for total cholesterol measurement?

uric acid and ascorbic acid inhibit the enzymes (false -), bilirubin and hemoglobin add color (false +)

What is the Friedewald formula for measuring LDL cholesterol?

LDL cholesterol = Total Cholesterol - [HDL + (triglyceride/5)]

What are the 2 limitations of the Friedewald formula?

1) has to be fasting because this formula does not account for chylomicrons

2) cannot use when triglyceride level is >400 mg/dL

How is LDL measured directly?

LDL is measured using the cholesterol reaction, but the with addition of a *blocking reagent* to block the contribution of HDL and VLDL forming a colored chromagen

What enzyme is used in triglyceride measurements to cleave the fatty acids from glycerol?

Lipase (bacterial)

What do both methods of triglyceride measurements measure?

Method #1:

Lipase → glycerol kinase → pyruvate kinase → lactate dehydrogenase

Measures *NAD*

Method #2 (endpoint colorimetric, most common)

Lipase → glycerol kinase → glycerophosphate oxidase → peroxidase

Measures a *colored product*

What is the most common interference of triglyceride measurement?

Endogenous free glycerol (will increase result by 10-20 mg/dL). Correct with reagent or do a glycerol blank reagent

How long must fasting be for lipid analysis?

10-12 hours

What is the most common chemical reagent that is used to isolate HDL from LDL and VLDL for measurement?

dextran sulfate

What are some potential interferences of HDL measurement?

Chylomicrons from non-fasting specimens and high triglyceride levels (so do a fasting specimen!)

What type of *antibody* is used to bind LDL and VLDL, so HDL can be measured?

antibody to B-100

What type of chemical is used as a blocking agent, enabling only HDL to react and *form colored product*?

synthetic polyanion reagent

What are the two methods used to measure apoprotein levels, and which is more common?

Nephelometry is the most common, can also use immunoassay

Which lipoprotein is Lp(a) associated with?

Lp(a) is an unusual type of *LDL* particle with an attached little a apoprotein

What type of *protein* is Lp(a) structurally similar to?

plasminogen

What medical condition is associated with increased levels of Lp(a)?

Lp(a) inhibits plasmin formation to the plasminogen --> clot formation --> occlusion --> myocardial infarction

What is the measurement method utilized for the measurement of Lp(a)?

ELISA