What cardiovascular score looks at the combination of apolipoprotein A (apo A), apolipoprotein B (apo B), and lipoprotein(a) (Lp(a))?

Cardiovascular Risk Assessment Using Apolipoprotein Profiles

Currently, there is no established cardiovascular risk score that specifically combines apolipoprotein A (apo A), apolipoprotein B (apo B), and lipoprotein(a) [Lp(a)] measurements for risk assessment. While these markers are individually valuable, guidelines do not recommend a specific combined score using all three parameters.

Current Recommendations for Apolipoprotein Testing

• Standard guidelines from the American College of Cardiology Foundation/American Heart Association (ACCF/AHA) do not recommend measurement of lipid parameters beyond standard fasting lipid profiles for cardiovascular risk assessment in asymptomatic adults 1
• The measurement of advanced lipid parameters, including apolipoproteins and Lp(a), has not consistently demonstrated significant improvement in risk prediction beyond traditional risk factors 1
• While these markers show associations with cardiovascular outcomes, they have not demonstrated substantial incremental value in risk reclassification compared to standard lipid measurements 1

Individual Value of Apolipoprotein Markers

Apolipoprotein B (apo B)

• Apo B directly reflects LDL particle numbers, as each LDL particle contains one molecule of apo B 1
• For high-risk patients, a target apo B level of <100 mg/dL is suggested, while for very high-risk patients, <80 mg/dL is recommended 2
• Apo B concentration reflects the total number of atherogenic lipoproteins and is recognized as a key lipid risk marker 3

Apolipoprotein A (apo A)

• Apo A-I is the major protein component of HDL and plays a crucial role in reverse cholesterol transport 2
• The relationship between apo A and HDL is less direct than that between apo B and LDL 1
• Clinical approaches focus more on lowering the apo B component of the apo B/apo A-I ratio, as evidence for this approach is stronger than for raising apo A-I 2

Lipoprotein(a) [Lp(a)]

• Lp(a) is composed of an apo B-containing lipoprotein to which apolipoprotein(a) is attached 4
• Elevated Lp(a) is an independent risk factor for cardiovascular disease and aortic stenosis 1
• Lp(a) adds independent prognostic value for coronary artery disease even after adjusting for apo B-containing particles 3
• Standardization of Lp(a) measurement remains challenging due to size heterogeneity of apo(a) 1

Emerging Research on Combined Markers

• Recent research suggests that adequate assessment of atherogenic risk from dyslipidemia is best accomplished by consideration of both apo B-containing particles and Lp(a) concentrations 3
• Lp(a) contributes on average 3% of apo B-containing particles in the general population, but up to 15% in individuals with the highest Lp(a) levels 5
• The association of Lp(a) with cardiovascular risk remains robust even after apo B adjustment, indicating its independent value 3

Clinical Implications

• When considering cardiovascular risk assessment, focus on standard lipid profiles first, as recommended by guidelines 1
• For refined risk assessment in selected patients, consider measuring apo B and Lp(a) separately rather than seeking a combined score 1, 3
• The Canadian Cardiovascular Society Guidelines suggest considering Lp(a) levels >30 mg/dL as abnormal 1
• For patients at high cardiovascular risk, monitoring both apo B and Lp(a) may provide complementary information 3

Important Caveats

• Measurement standardization remains a significant challenge, particularly for Lp(a) 1
• Different assays express Lp(a) levels either in mg/dL (mass) or nmol/L (molar concentration), with no reliable conversion factor between units 1
• The clinical utility of these markers in specific populations (post-ACS, FH, chronic renal failure, diabetes, elderly) requires further study 1
• Genetic factors significantly influence Lp(a) levels, and polygenic risk scores may help identify individuals who would benefit most from testing 6