Serum Cholesterol

Question 0

Optical path

Answer 0

1 cm

Question 1

Specimen

Answer 1

Serum
EDTA- plasma
Heparinized plasma

Question 2

Reagent stability

Answer 2

Unopened - up to the expiry date (2-8 Celsius)
Opened - 6 weeks (2-8 Celsius)
Opened - 2 weeks (15-25 Celsius)

Question 3

Recommended initial tests for evaluating blood cholesterol

Answer 3

Complete lipoprotein profile (TC, LDL-C, HDL-C, TAG)

Question 4

Reaction principle

Answer 4

Cholesterol ester + water (CHE) —> cholesterol + fatty acid
Cholesterol + oxygen (CHO) —> cholestene-3-one + hydrogen peroxide
2 hydrogen peroxide + 4-aminoantipyrine + phenol (POD) —> quinoneimine + 4 water

Question 4

Formation of the indicator

Answer 4

Hydrogen peroxide and 4-aminoantipyrine in the presence of phenol and peroxidase

Question 5

Preservative of reagents

Answer 5

Sodium azide (0.05%)

Question 6

Values that do not influence serum cholesterol test

Answer 6

Hemoglobin values up to 200 mg/dL

Bilirubin values up to 5 mg/dL

Question 7

Temperature

Answer 7

20-25 Celsius

37 Celsius

Question 8

Indicator

Answer 8

Quinoneimine

Question 10

Reagent composition

Answer 10

Phosphate buffer (pH 6.5)
4-aminoantipyrine
Phenol
Peroxidase
Cholesterolesterase
Cholesteroloxidase
Sodium azide

Question 11

Linearity

Answer 11

Up to a cholesterol concentration of 750 mg/dL or 19.3 mmol/L

Question 12

Calculation of the cholesterol concentration (mmol/L)

Answer 12

C = 5.17 x Absorbance (sample)/Absorbance (standard)

Question 13

Wavelength

Answer 13

500 nm, Hg 546 nm

Question 14

Incubation period

Answer 14

20 minutes at 20-25 Celsius

10 minutes at 37 Celsius

Question 15

Blood cholesterol tests should be performed

Answer 15

in all adults aged 20 years and older, and should be repeated at least once every 5 years.

Question 16

Clinical interpretation

Answer 16

Desirable = < 200 mg/dL
Borderline high = 200-239 mg/dL
High = >/= 240 mg/dL

Question 17

Serum cholesterol is determined after

Answer 17

Enzymatic hydrolysis

Oxidation

Question 18

Calculation of the cholesterol concentration (mg/dL)

Answer 18

C = 200 x Absorbance (sample)/Absorbance (standard)