APOLIPOPROTEINS - serum

---

Specimen: 5 mL blood in plain tube. Genotyping requires collection of a suitable specimen eg 5 mL blood in a lithium heparin tube.

Method: Immunoassay. The apolipoproteins usually quantitated are apoA1, apoB and apo(a); apoE genotyping or phenotyping may also be done.

Reference Intervals:

Apolipoprotein A1 (apoA1):	1.0-1.8 g/L
Apolipoprotein B (apoB):	0.8-1.6 g/L
Apolipoprotein (a) (apo[a]):	Depends on method, and whether lipoprotein (a) or apo(a) is being measured.

Application: ApoA1 and apoB may be measured as an alternative to HDL and LDL cholesterol respectively in the assessment of atherosclerosis risk factors, however they do not appear to offer any advantage. ApoB together with LDL cholesterol can be used to define hyperapobetalipoproteinaemia, a condition with normal LDL cholesterol but increased risk of atherosclerosis. Apo(a) is an independent risk factor for atherosclerosis and may be indicated in the assessment of a patient with premature coronary or cerebral arterial disease, esp if there is a suggestive family history. ApoE genotyping is done in patients with type III hyperlipidaemia. It may be used to identify some patients at risk of developing Alzheimer’s disease but the ethical implications of such testing remain controversial. ApoA1 and apoB are very low in Tangier disease and abetalipoproteinaemia respectively.

Interpretation: Decreased apoA1 and increased apoB or apo(a) are associated with an increased risk of atherosclerosis. Homozygous apoE2 may result in type III hyperlipidaemia. Homozygous apoE4 may be associated with an increased risk of Alzheimer’s disease.

Reference: Naito HK. J Clin Immunoassay 1986; 9: 11-20.

---