Estimation of HDL Cholesterol

By /

Introduction

  1. HDL cholesterol represents a fraction of total serum cholesterol carried by HDL particles.
  2. HDL particles are small, dense, and protein-rich lipoproteins that facilitate cholesterol efflux from cells.
  3. They are anti-atherogenic due to their role in cholesterol removal and their anti-inflammatory and antioxidant properties.
  4. Determining HDL cholesterol is a standard part of lipid panel testing, including total cholesterol, LDL cholesterol, triglycerides, and HDL cholesterol.
  5. Measuring HDL cholesterol is crucial for assessing cardiovascular risk, as reduced HDL levels are an independent risk factor for atherosclerosis and coronary artery disease.
  6. This document provides a comprehensive overview of HDL cholesterol determination, including methods, principles, sample requirements, reagents, procedures, calculations, normal ranges, and clinical significance.

Principles

  1. Precipitation Methods:
    • Non-HDL lipoproteins (LDL, VLDL, chylomicrons) are precipitated from serum using reagents such as heparin-manganese chloride, phosphotungstate-magnesium, or dextran sulfate.
    • The supernatant, containing HDL cholesterol, is analyzed enzymatically using the cholesterol oxidase-peroxidase method.

Cholesterol Esters → Cholesterol Esterase → Free Cholesterol + Fatty Acids

Free Cholesterol + O2 →   Cholesterol Oxidase  → Cholest-4-en-3-one+H2O2

H2O2 + Chromogen →   Peroxidase  → Colored Compound

  1. Direct HDL-C Assays:
    • Utilize specific enzymes or detergents to selectively isolate HDL cholesterol without precipitating other lipoproteins.

Sample Collection

  1. Sample Type:
    • Serum or plasma (heparin or EDTA-treated) can be used.
  2. Patient Preparation:
    • A 12-hour fasting sample is preferred to minimize interference from triglycerides.
  3. Storage:
    • Samples can be stored at 2–8°C for up to 7 days or frozen at -20°C for long-term storage.

Reagents

  1. HDL-Cholesterol (Enzymes-Chromogen Buffer)   
  2. HDL-Cholesterol (Diluent) 
  3. HDL – Cholesterol (Precipitating Reagent) Ready for use 
  4. HDL – Cholesterol Standard. (50 mg/dl)      

Procedure

Test Standard Blank
Reagents, ml 1 ml 1 ml 1 ml
Standard, ml – 0.05 ml –
Sample, ml 0.05 ml – –
Distilled water, ml – – 0.05 ml

Mix well, incubate for ten minutes at 37oC, and read the absorbance of test and standard against reagent blank at 505nm (500-540 Green filter).

Calculation

HDL cholesterol concentration is calculated using the following formula:

HDL C (mg/dL) = Absorbance of Sample /Absorbance of Standard × Concentration of Standard (mg/dl)

Normal Range

The reference range for HDL cholesterol is:

  • Men: 40–60 mg/dL (≥40 mg/dL is considered protective)
  • Women: 50–60 mg/dL (≥50 mg/dL is considered protective)
  • Optimal HDL-C: >60 mg/dL (associated with reduced cardiovascular risk)
  • Low HDL-C: <40 mg/dL (associated with increased cardiovascular risk)

Clinical Significance

Increased HDL Cholesterol

Raised HDL cholesterol levels are generally considered beneficial because they help protect blood vessels from cholesterol deposition.

Causes of increased HDL cholesterol

  • Regular physical exercise
  • Weight reduction
  • Healthy diet rich in unsaturated fats
  • Estrogen effect in females
  • Moderate alcohol intake
  • Certain lipid-lowering drugs

Clinical importance of increased HDL

  • Reduces the risk of Atherosclerosis
  • Protects against coronary artery disease
  • Improves reverse cholesterol transport
  • Reduces cholesterol accumulation in arterial walls

Decreased HDL Cholesterol

Low HDL cholesterol is clinically significant because it increases the risk of cardiovascular disease.

Causes of decreased HDL cholesterol

  • Diabetes Mellitus
  • Obesity
  • Smoking
  • Sedentary lifestyle
  • Hypertriglyceridemia
  • High carbohydrate intake
  • Chronic kidney disease
  • Liver disease

Clinical importance of low HDL

  • Increased risk of coronary artery disease
  • Increased risk of myocardial infarction
  • Increased risk of metabolic syndrome
  • Promotes cholesterol deposition in blood vessels

Myocardial Infarction

Role in Cardiovascular Risk Assessment

HDL cholesterol is routinely evaluated along with:

  • Total cholesterol
  • LDL cholesterol
  • Triglycerides

MCQs

1. HDL stands for:

A. High-density lipoprotein
B. Heavy-density lipid
C. High-density lipid
D. Hepatic density lipoprotein

Answer: A. High-density lipoprotein

2. HDL is commonly called:

A. Bad cholesterol
B. Good cholesterol
C. Neutral fat
D. Harmful lipid

Answer: B. Good cholesterol

3. Main function of HDL is:

A. Carry triglycerides to tissues
B. Carry cholesterol from tissues to liver
C. Store fat in adipose tissue
D. Produce cholesterol

Answer: B. Carry cholesterol from tissues to liver

4. HDL protects against:

A. Fever
B. Atherosclerosis
C. Anemia
D. Leukemia

Answer: B. Atherosclerosis

5. HDL cholesterol is estimated as part of:

A. CBC
B. Lipid profile
C. LFT
D. KFT

Answer: B. Lipid profile

6. HDL cholesterol is measured in:

A. IU/L
B. mg/dL
C. g/L
D. mmol only

Answer: B. mg/dL

7. Normal HDL level in men is:

A. More than 40 mg/dL
B. Less than 20 mg/dL
C. More than 100 mg/dL
D. Less than 10 mg/dL

Answer: A. More than 40 mg/dL

8. Normal HDL level in women is:

A. More than 50 mg/dL
B. Less than 20 mg/dL
C. 10 mg/dL
D. 15 mg/dL

Answer: A. More than 50 mg/dL

9. Protective HDL level is:

A. 20 mg/dL
B. 30 mg/dL
C. 60 mg/dL and above
D. 10 mg/dL

Answer: C. 60 mg/dL and above

10. HDL removes cholesterol by:

A. Forward transport
B. Reverse cholesterol transport
C. Direct excretion
D. Oxidation

Answer: B. Reverse cholesterol transport

11. HDL is synthesized mainly in:

A. Liver
B. Bone
C. Muscle
D. Brain

Answer: A. Liver

12. The sample used for HDL estimation is:

A. Whole blood
B. Serum
C. CSF
D. Urine

Answer: B. Serum

13. Fasting required before HDL estimation is:

A. 2 hours
B. 4 hours
C. 10–12 hours
D. 24 hours

Answer: C. 10–12 hours

14. HDL estimation commonly uses:

A. Precipitation method
B. Titration
C. Flame photometry
D. Electrophoresis

Answer: A. Precipitation method

15. Precipitating reagent removes:

A. HDL
B. LDL and VLDL
C. Proteins
D. Glucose

Answer: B. LDL and VLDL

16. One precipitating reagent used is:

A. Sodium chloride
B. Phosphotungstate
C. Urea
D. Glucose

Answer: B. Phosphotungstate

17. Another reagent used with phosphotungstate is:

A. Magnesium chloride
B. Potassium chloride
C. Calcium chloride
D. Sodium sulfate

Answer: A. Magnesium chloride

18. HDL remains in:

A. Precipitate
B. Supernatant
C. Sediment
D. Pellet

Answer: B. Supernatant

19. Cholesterol esterase converts:

A. Cholesterol ester to cholesterol
B. Fat to glucose
C. Glycerol to fat
D. Protein to cholesterol

Answer: A. Cholesterol ester to cholesterol

20. Cholesterol oxidase produces:

A. Water
B. Hydrogen peroxide
C. Nitrogen
D. Oxygen only

Answer: B. Hydrogen peroxide

21. Peroxidase forms:

A. Gas
B. Colored complex
C. Fat
D. Protein

Answer: B. Colored complex

22. HDL estimation is read by:

A. Microscope
B. Spectrophotometer
C. Centrifuge
D. Thermometer

Answer: B. Spectrophotometer

23. Increased HDL is:

A. Harmful
B. Beneficial
C. Neutral
D. Dangerous

Answer: B. Beneficial

24. Exercise causes:

A. Decreased HDL
B. Increased HDL
C. No effect
D. HDL disappearance

Answer: B. Increased HDL

25. Smoking causes:

A. Increased HDL
B. Decreased HDL
C. No change
D. HDL doubling

Answer: B. Decreased HDL

26. Obesity usually causes:

A. Increased HDL
B. Decreased HDL
C. No effect
D. Very high HDL

Answer: B. Decreased HDL

27. Diabetes commonly causes low HDL:

A. True
B. False

Answer: A. True

28. HDL is protective against coronary artery disease:

A. True
B. False

Answer: A. True

29. Low HDL increases risk of:

A. Infection
B. Heart disease
C. Fracture
D. Anemia

Answer: B. Heart disease

30. HDL is called anti-atherogenic lipoprotein:

A. True
B. False

Answer: A. True

31. Female hormones generally:

A. Lower HDL
B. Raise HDL
C. Destroy HDL
D. No effect

Answer: B. Raise HDL

32. Sedentary lifestyle causes:

A. High HDL
B. Low HDL
C. No effect
D. HDL elimination

Answer: B. Low HDL

33. HDL is lowest in:

A. Athletes
B. Smokers
C. Healthy adults
D. Active persons

Answer: B. Smokers

34. HDL helps remove cholesterol from:

A. Liver
B. Peripheral tissues
C. Kidney only
D. Bone marrow

Answer: B. Peripheral tissues

35. HDL carries cholesterol to:

A. Kidney
B. Liver
C. Brain
D. Muscle

Answer: B. Liver

36. Increased HDL lowers risk of Myocardial Infarction

A. True
B. False

Answer: A. True

37. HDL belongs to:

A. Protein metabolism
B. Lipid metabolism
C. Carbohydrate metabolism
D. Mineral metabolism

Answer: B. Lipid metabolism

38. HDL is measured after:

A. Centrifugation
B. Heating
C. Filtration only
D. Boiling

Answer: A. Centrifugation

39. Alcohol in moderate amount may:

A. Increase HDL
B. Decrease HDL
C. Destroy HDL
D. No effect

Answer: A. Increase HDL

40. Low HDL is common in metabolic syndrome:

A. True
B. False

Answer: A. True

41. HDL is synthesized partly in intestine:

A. True
B. False

Answer: A. True

42. HDL contains highest proportion of:

A. Protein
B. Fat
C. Water
D. Sugar

Answer: A. Protein

43. HDL is densest lipoprotein:

A. True
B. False

Answer: A. True

44. Low HDL and high LDL is:

A. Protective
B. High risk combination
C. Normal
D. Beneficial

Answer: B. High risk combination

45. HDL estimation helps in:

A. Lipid disorder diagnosis
B. Anemia diagnosis
C. Infection diagnosis
D. Thyroid diagnosis

Answer: A. Lipid disorder diagnosis

46. Liver disease may lower HDL:

A. True
B. False

Answer: A. True

47. Weight reduction usually:

A. Raises HDL
B. Lowers HDL
C. No change
D. Stops HDL formation

Answer: A. Raises HDL

48. HDL protects blood vessels:

A. True
B. False

Answer: A. True

49. High carbohydrate diet may lower HDL:

A. True
B. False

Answer: A. True

50. HDL estimation is important in preventive medicine:

A. True
B. False

Answer: A. True

Scroll to Top
Enable Notifications OK No thanks