Does a patient need to fast before apolipoprotein B (apo B) and lipoprotein(a) (Lp(a)) testing?

Fasting Requirements for Apolipoprotein B and Lipoprotein(a) Testing

Patients do not need to fast before apolipoprotein B (apo B) or lipoprotein(a) [Lp(a)] testing, as both markers are minimally affected by food intake and can be reliably measured in the non-fasting state.

Apolipoprotein B Testing

Apo B levels are not significantly affected by fasting status and can be measured without fasting. 1

• The 2018 AHA/ACC Guideline explicitly addresses apo B measurement in the context of lipid testing, noting that it can be measured alongside standard lipid panels 1
• Since apo B is the major apolipoprotein embedded in LDL and VLDL particles, its concentration reflects the total number of atherogenic particles rather than their lipid content 1
• The guideline recommends non-fasting samples as generally adequate for lipid assessment, with no specific fasting requirement mentioned for apo B 1
• Apo B measurement is particularly useful when triglycerides are ≥200 mg/dL, and can be performed on the same non-fasting sample used for standard lipid testing 1

Lipoprotein(a) Testing

Lp(a) levels remain stable regardless of fasting status and should be measured without requiring patients to fast. 2, 3

• A large population study of 34,829 individuals demonstrated that Lp(a) levels do not change in response to normal food intake: median fasting levels were 17.3 mg/dL versus 19.4 mg/dL at 3-4 hours post-meal (p=0.38) 3
• The European Atherosclerosis Society and European Federation of Clinical Chemistry joint consensus statement explicitly states that Lp(a) concentrations are not affected by fasting/non-fasting status 2
• The predictive ability of Lp(a) for ischemic heart disease and myocardial infarction is not affected by fasting status 3
• The 2018 AHA/ACC Guideline discusses Lp(a) measurement without any fasting requirement, indicating it can be measured on non-fasting samples 1

Clinical Implementation

Order both apo B and Lp(a) on non-fasting samples to improve patient compliance and convenience without compromising test accuracy. 4, 2

• Non-fasting lipid testing, including apo B and Lp(a), represents a simplification for patients, laboratories, and clinicians without negative implications for cardiovascular disease risk assessment 5
• The only lipid parameter significantly affected by fasting status is triglycerides, which increase by approximately 26 mg/dL in non-fasting samples 4, 2, 5
• If triglycerides are ≥400 mg/dL on initial non-fasting testing, a repeat fasting sample should be obtained 4

Important Caveats

• While Lp(a) levels are minimally increased with elevated C-reactive protein (CRP >10 mg/dL: median Lp(a) 21.1 mg/dL versus CRP <1 mg/dL: median 18.0 mg/dL), this change is not clinically significant and does not affect its predictive value 3
• Lp(a) should typically be measured only once in a lifetime, as levels are primarily genetically determined and remain stable over time 1
• The 2018 AHA/ACC Guideline recommends measuring Lp(a) in patients with family history of premature ASCVD or personal history of ASCVD not explained by major risk factors, with values ≥50 mg/dL or ≥125 nmol/L considered a risk-enhancing factor 1