1. Investigation of hyperlipidaemia
Dr. S Homathy

2. Properties of lipids Hydrophobic High-energy food
For cell membranes, steroid hormones
Some lipids essentially exogenous

3. Lipo-protein structure
Fat globule in water
Central hydrophobic core
Triglycerides
Esterified cholesterol
Outer shell
Apoproteins
Phospholipids
Non-esterified cholesterol

4. Types of lipo-proteins
High density (HDL)
Low density (LDL)
Very low density (VLDL)
Intermediate density (IDL)
Chylomicrons

5. Primary Functions HDL -Cholesterol from tissue to liver
LDL -Cholesterol to tissue
VLDL -Endogenous triglycerides
IDL -Transient form
Chylomicron -Exogenous triglycerides

6. Broad basedly …
HDL = GOOD Cholesterol
LDL = BAD Cholesterol

7. Composition of lipoproteins
HDL -50% proteins
LDL -55% Cholesterol
VLDL -55% Triglycerides
Chylomicron -90% Triglycerides

8. Apoproteins in lipoproteins
HDL - A, C, E
LDL - B
VLDL - B, C, E.
Chylomicron - A, B, (C, E.)

9. Electrophoretic mobility of lipoproteins
HDL - alpha
LDL - beta
VLDL - pre-beta
Chylomicron - origin

10. Reference method for measurement of lipoproteins
ULTRA CENTRIFUGATION
Lipo protein floatation rate measured in Svedberg units

11. Laboratory investigations
Serum total cholesterol
Serum lipid profile
Apo lipoprotein levels
Lipid electrophoresis
Special tests –geno typing

12. Total cholesterol Usually fasting Non-fasting accaptable for screening
<200 mg/dl (5.2 mmol/l) is desirable.
>200 mg/dl (5.2 mmol/l) proceed to a lipid profile.

13. Secondary causes of hyperlipidaemia
Diabetes mellitus
Hypothyroidism
Nephrotic syndrome
Obstrucive jaundice
Alcohol abuse (Tg)

14. Lipid Profile Fast for 10 – 12 hours.
Normal lipid diet, constant weight
Not on drug affecting lipids (OCP)
Not on lipid lowering drugs unless being monitored.
No stress (3 months after MI)
Standardised collection procedure

15. Overnight serum
Observe after keeping fasted serum in a test tube at 4C for 18 hours.
Milky layer on top -chylomicrons
Turbid serum -VLDL
Clear -Normal / LDL

16. Lipid profile Measure Total Cholesterol HDL Cholesterol Triglycerides
Calculate LDL Cholesterol
Cardiac risk ratio

17. Friedewald formula Total cholesterol = HDL + LDL + VLDL
VLDL = Tg(in mg/dl) / 5
= Tg (in mmol/l) / 2.2
Formula not valid if Triglycerides are > 400 mg/dl (4.5 mmol/l)

18. Cardiac risk ratio Total cholesterol / HDL cholesterol
> 5 is unfavourable
Apo A1 / Apo B ratio

19. Interpretation Total Cholesterol <200 Desirable
Borderline high
 High

20. LDL Cholesterol
<100 Optimal Near normal or above normal Border line high High 190 Very high

21. HDL Cholesterol
<40 Low >60 High

22. Triglicerides
<150 Normal Borderline high High  500 Very high

23. Apolipoprotein levels
Apolipoprotein A 1- reflects HDL
Apolipoprotein B - reflects LDL
Apolipoprotein a - independent risk factor for MI

24. Lipid electrophoresis
Serum electrophoresis is done
Stain with a lipid staining dye
Fredrickson’s Classification based on this.

25. Fredrickson’s classification of hyperlipidaemia
Type Pattern Lipoproteins
I origin chylomicrons
II a b-lipoprotein LDL
II b pre b & b VLDL + LDL
III broad b IDL
IV pre-b VLDL
V origin & pre b Chylo + VLDL

26. Special tests
Apo E genotyping
using PCR technique

27. Conversion factors Cholesterol mg/dl / 38.6 = mmol/l
Triglyceride mg/dl / 88.5 = mmol/l

28. Summary Screening test Total Cholesterol Confirming test Lipid profile
Phenotyping Lipid electrophoresis
Geno typing PCR technology
Monitoring tests Lipid profile