Yes, there are multiple apolipoprotein laboratory tests available.
Laboratories should offer at least two distinct apolipoprotein tests as individually orderable assays: Apolipoprotein B (ApoB) and Lipoprotein(a) [Lp(a)], which measures apolipoprotein(a). 1
Available Apolipoprotein Tests
The clinically relevant apolipoprotein tests include:
Primary Clinical Tests
- Apolipoprotein B (ApoB) - Measures the protein component of LDL and other atherogenic lipoproteins, reported in g/L 1
- Lipoprotein(a) [Lp(a)] - Measures apolipoprotein(a) bound to ApoB, reported in nmol/L 1
Additional Measurable Apolipoproteins
Research-grade multiplex LC-MS/MS assays can quantify additional apolipoproteins including:
- Apolipoprotein A-I (ApoA-I) - The major protein of HDL 2, 3, 4
- Apolipoprotein C-I, C-II, C-III - Components of triglyceride-rich lipoproteins 2, 4
- Apolipoprotein E (ApoE) - Involved in lipoprotein metabolism, with phenotyping capability 2, 4
Clinical Implementation
Canadian guidelines specifically recommend that ApoB and Lp(a) be offered only as individually orderable tests, not as part of routine lipid panels. 1 This differs from the standard lipid panel (total cholesterol, LDL-C, HDL-C, non-HDL-C, triglycerides) which should be offered together.
Key Testing Specifications
For Lp(a) specifically:
- Must use assays calibrated in molar units (nmol/L) traceable to WHO/IFCC reference material 1
- The specific assay used must be stated on the report due to lack of complete standardization 1
- Measure once in a lifetime during initial lipid screening, as levels are genetically determined and stable 1
- Decision threshold: ≥100 nmol/L (or ≥50 mg/dL) warrants more intensive cardiovascular risk management 1, 5
For ApoB:
- Reported in g/L with traceability to WHO/IFCC SP3 reference material 1
- Decision thresholds: ≥1.05 g/L for intermediate risk, ≥1.45 g/L for low risk patients 1
- Preferred over LDL-C when triglycerides >1.5 mmol/L 6, 1
Important Caveats
While ApoA-I and the ApoB/ApoA-I ratio have been studied extensively 7, 8, current Canadian guidelines do not recommend routine ApoA-I testing or ratio calculations for clinical practice 1. The focus remains on ApoB and Lp(a) as individually orderable tests that provide actionable cardiovascular risk information beyond traditional lipid panels.
The distinction matters clinically: ordering "apolipoprotein testing" requires specifying which apolipoprotein, as ApoB and Lp(a) serve different clinical purposes and have different decision thresholds for cardiovascular risk stratification.