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CC1 > Lec 15: Lipid Methodologies > Flashcards

Lec 15: Lipid Methodologies Flashcards

1
Q

Most common indications for ordering a complete lipid profile includes:

A
  • screening for a familial lipid disorder
  • establishing the risk of cardiovascular disease in an individual without prior disease
  • the first lipid test in any patient being tested for a lipid disorder
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2
Q
  1. [TRUE or FALSE] Cholesterol levels remain constant with age.
  2. What hormone in women has cardiovascular protective effects wherein levels are lower before adolescence and after menopause?
A
  1. FALSE
    • cholesterol levels rise with age
  2. Estrogen
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3
Q
  1. Cholesterol screening should be repeated every ____ years.
  2. [TRUE or FALSE] Lipids are easily altered by recent dietary intake.
  3. Dietary intake of ___ & ___ significantly influences plasma lipid levels
A
  1. 5 years
  2. TRUE
  3. Saturated fat, cholesterol
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4
Q
  1. For lipid panel testing, how many weeks should the patient be on their usual diet?
  2. What medications alter lipid levels? (Include their effect)
  3. Lipoprotein measurements are made:
    a. ___ after infection/trauma
    b. ___ after childbirth
A
  1. Two weeks, neither gaining nor losing weight.
  2. Oral contraceptives & postmenopausal estrogens
    • false increase in cholesterol
    Some antihypertensive drugs
    • false increase in lipid levels
  3. a. 8 weeks
    b. 3 to 4 months
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5
Q

Give the effects (increase/decrease) of the following:

  1. Thyroid, kidney, liver disease
  2. High fat diet
  3. Diet rich in sucrose
  4. Ingesting monounsaturated & polyunsaturated FA
  5. In the middle of a menstrual cycle
A
  1. increase in lipids & lipoproteins
  2. Increases serum triglycerides
  3. Increases triglycerides
  4. Reduce cholesterol
  5. Increase cholesterol & triglycerides, maximum estrogen secretion
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6
Q
  1. Patients should fast at least ___ before Venipuncture.
  2. Why is water intake permitted during fasting?
A
  1. 10 to 12 hours
  2. Lipids are nonpolar, so water does not affect the lipids nor interfere with the test.
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7
Q

Storage conditions for serum/plasma when analysis is delayed.

A

Refrigerated at 4°C for several days to one week

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8
Q
  1. Before taking the sample, the patient should be seated for ___ minutes to prevent ___.
  2. Effect of hemoconcentration.
  3. Effect of a recumbent position
A
  1. For 5 minutes, to prevent hemoconcentration
  2. Increases cholesterol by 10-15%
  3. 10% decrease in concentrations of TC , LDL-C, HDL-C
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9
Q
  1. Specimen of choice
  2. Preferred sample for electrophoretic/ultracentrifugation methods
  3. Anticoagulant of choice
  4. Anticoagulants avoided (include effects)
A
  1. Serum, Plasma
  2. Plasma
  3. EDTA
  4. Citrate
    • false decreased lipoprotein concentration
    Heparin
    • affects electrophoresis results
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10
Q

Liebermann Burchard Reaction

  1. Principle
  2. Components of Liebermann Burchard reagent
  3. Wavelength used
  4. End Product (color & name)
  5. What chemical mixture was used for precipitation & extraction?
A
  1. Acetic anhydride reacts with Cholesterol in a Chloroform solution to form a blue green color.
  2. Sulfuric Acid, Acetic anhydride
  3. 620 mm
  4. Cholestahexaene sulfonic acid (Blue green)
  5. Alcohol acetone mixture
    • Alcohol precipitates proteins
    • Acetone extracts lipids
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11
Q

Bloor Method

  1. Principle
  2. End Product (color)
  3. What chemical mixture was used for precipitation & extraction?
  4. Function of Chloroform
  5. Color developer
A
  1. Cholesterol is extracted with alcohol ether mixture, and it is measured with LB reaction
  2. Green
  3. Alcohol ether mixture
    • Alcohol precipitates proteins
    • Ether extracts lipids
  4. Extracts cholesterol residue
  5. Conc. Sulfuric Acid & Acetic anhydride (LB reagent)
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12
Q

Abell-Kendall Method

  1. Chemical used to hydrolyze cholesterol
  2. Chemical used to extract cholesterol
  3. End product (color)
A
  1. Alcoholic KOH
  2. Petroleum jelly
  3. Blue green
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13
Q

Cholesterol Oxidase Method
(routine method)

  1. Enzymes in the first reaction
  2. Enzyme in the 2nd reaction
  3. Chromogens
A
  1. Cholesteryl esterase, Cholesterol oxidase
  2. Peroxidase
  3. Phenol, 4-aminoantipyrine
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14
Q

Cholesterol FS

  1. Reagent used (except the ones mentioned in COD)
  2. Anticoagulants used
  3. Anticoagulant avoided
  4. Wavelength used
  5. Interferences
  6. Is this method specific for cholesterol?
A
  1. Good’s buffer
  2. Heparin, EDTA
  3. Citrate
  4. 500 nm, Hg 546 nm
  5. Ascorbic acid, bilirubin
  6. No
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15
Q

This method is the current reference method and it is used to specifically measure cholesterol. This method shows agreement with the gold standard.

A

Gas chromatography - mass spectrometry

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16
Q

The reference method used by CDC for measurement of triglycerides.

A

Van Handel and Zilversmith method

17
Q

Van Handel and Zilversmith Method

  1. Chemical used for extraction
  2. The adsorbent used and function.
  3. Chemical used for hydrolysis
  4. End product (color)
A
  1. Floch’s reagent
    • Chloroform ethanol mixture
  2. Aluminum
    • removal of phospholipids
  3. Alcoholic KOH
    • hydrolyzed TAG —> glycerol, fatty acids
  4. Blue
18
Q

PRECAUTIONS

  1. Why are cholesterol levels slightly higher in the plasma than serum?
  2. Anticoagulants avoided (increase/decrease)
  3. TG determination interferences (increase/decrease)
A
  1. Chylomicrons & lipoproteins are trapped in the clot. Triglycerides might sink with the clot.
  2. Flourides, Oxalate
    • false increase
  3. Ascorbic acid, bilirubin, hemolysis
    • hemolysis releases hemoglobin which leads to false decrease.
19
Q

Testing Considerations: LIPOPROTEIN SEPARATION METHOD

  • A method that separates lipoproteins by class on the basis of density
  • not used in the clinical laboratory
  • for research purposes
A

Ultracentrifugation

20
Q

Testing Considerations: LIPOPROTEIN SEPARATION METHOD

  1. Separation of lipoproteins on the basis of charge
  2. Arrange the lipoproteins from highest to lowest charge, and state their electrophoretic mobility.
  3. In the reaction, what produces a red color?
A
  1. Electrophoresis
  2. highest to lowest:
    • HDL - alpha region
    • LDL - beta region
    • VLDL - pre-beta region
    • Chylomicron - origin
  3. Ester bonds
21
Q

Testing Considerations: LIPOPROTEIN SEPARATION METHOD

• most of the time used to separate HDL
• APO-B lipoprotein will sink in the precipitate, and HDL will be left in the supernatant to be measured.

A

Polyanion precipitation

22
Q

Polyanion Precipitation

What are the polyanions used?

A
  • phosphotungstate
  • heparin sulfate
  • dextran sulfate
23
Q

• reference method for LDL determination
• combines ultracentrifugation & chemical precipitation

A

BETA QUANTIFICATION

  • Ultracentrifugation removes VLDL and Chylomicrons.
  • Chemical precipitation precipitates HDL
24
Q

• reference method for HDL determination
• mixes ultracentrifugation & precipitation
• analysis of supernatant cholesterol by the Abell-Kendall assay

A

CDC-RMP

  • Ultracentrifugation removes VLDL
  • Heparin manganese removes LDL
  • supernatant contains HDL
25
Q

Friedewald Calculation

A
  • indirect measurement of LDL

Formula for mg/dL:
LDL = Total Chol – HDL - (TG) ÷ 5

Formula for mmol/L:
LDL = Total Chol – HDL - (TG) ÷ 2.175

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