Apolipoprotein A1
What it measures, and what changes the number.
Apolipoprotein A1 is the main protein component of HDL particles, the lipoproteins that carry cholesterol away from tissues toward the liver. The test measures the concentration of this protein in the blood, which gives a view of HDL that does not depend on how much cholesterol each particle carries.
It is typically read alongside HDL cholesterol and apolipoprotein B, since the balance between the protein of HDL and the protein of the atherogenic particles is often compared. A standard lipid panel and lipoprotein(a) are frequently on the same request.
Unlike triglycerides, apolipoprotein A1 changes little after a meal, so fasting matters less, though many labs still collect it with a fasting lipid panel. It is measured by immunoassay, commonly nephelometry or turbidimetry. Reports may show it as Apolipoproteína A1.
Often read alongside: HDL cholesterol, Apolipoprotein B, Total cholesterol, Triglycerides, Lipoprotein(a)