Apo A1 and Apo B Testing: Fasting Requirements

Apolipoprotein A1 and Apolipoprotein B testing does not require fasting, making these tests more convenient than traditional lipid panels. 1

Key Testing Requirements

The assay does not require fasting conditions and is not sensitive to moderately high triglyceride levels, according to the European Society of Cardiology/European Atherosclerosis Society guidelines 1
Blood samples can be collected at any time of day without affecting test accuracy 1
This represents a significant practical advantage over traditional lipid testing, which requires 12-hour fasting for accurate triglyceride and LDL-C measurements 1

Apolipoprotein A1, apolipoprotein B, and the apo B/apo A1 ratio show very low diurnal variation, typically with coefficients of variation below 2% 2
Sampling time does not significantly affect results, whether during day or night 2
This stability further supports the convenience of non-fasting measurement 2

Apo B represents the total number of atherogenic particles (VLDL, IDL, and LDL) in plasma, with each atherogenic particle containing exactly one apo B molecule 1
Apo B has been shown in prospective studies to be equal to LDL-C in cardiovascular risk prediction 1
Target levels depend on cardiovascular risk stratification:
- Very high-risk patients: <80 mg/dL 3
- High-risk patients: <100 mg/dL 3

Apo A1 is the major protein of HDL and provides a good estimate of HDL particle concentration 1
Low levels are defined as:
- Men: <120 mg/dL 1
- Women: <140 mg/dL 1
Each HDL particle may carry several apo A1 molecules 1

The apo B/apo A1 ratio represents the balance between atherogenic and antiatherogenic lipoproteins and is a strong predictor of cardiovascular risk 4, 5
The ratio is superior to traditional cholesterol ratios (TC/HDL-C, LDL-C/HDL-C, non-HDL-C/HDL-C) in predicting coronary disease risk 4
A ratio >0.9 is considered high risk for cardiovascular disease 5
The ratio shows the lowest diurnal variation of all lipid markers, typically <2% 2

Good immunochemical methods are available and easily run in conventional autoanalyzers 1
Analytical performance is excellent with standardized measurements 1, 4
No need for fasting eliminates patient inconvenience and improves compliance 1
Results are not affected by moderately elevated triglycerides, unlike calculated LDL-C 1

Apo B/apo A1 ratio is particularly valuable in patients with metabolic syndrome, diabetes, or chronic kidney disease where traditional lipid measurements may be misleading 1
The ratio is especially useful when LDL-C levels are <3.6 mmol/L (140 mg/dL), where it provides superior risk prediction 4
Apo B is a better marker of atherogenic particle burden in patients with high concentrations of small dense LDL particles 1

Despite theoretical advantages, TC and LDL-C remain the primary treatment targets supported by the strongest evidence base from clinical trials 1
Apo B has not been evaluated as a primary treatment target in prospective statin trials, only in post-hoc analyses 1
Apo A1 should not be treated as a therapeutic target, as there is no evidence that pharmacologically raising apo A1 improves cardiovascular outcomes 6
The therapeutic focus should be on lowering apo B when treatment is needed, as evidence for apo B reduction is substantially stronger than for raising apo A1 7, 6, 3

Consider apo B and apo A1 testing as alternative or complementary markers to traditional lipids 1
Particularly useful for risk assessment in patients with:
- Metabolic syndrome 1
- Diabetes 1
- Chronic kidney disease 1
- Hypertriglyceridemia 1
The apo B/apo A1 ratio may be valuable for fine-tuning risk assessment in clinical practice 7