Lipoprotein(a)
What it measures, and what changes the number.
Lipoprotein(a), often written Lp(a), is a cholesterol carrying particle similar to LDL but with an extra protein called apolipoprotein(a) attached. The test measures how much Lp(a) is present in the blood. Its level is largely inherited and changes little over a lifetime, so it is often measured only once or rarely.
It is usually read alongside the standard lipid panel, especially LDL cholesterol, and with apolipoprotein B, since each Lp(a) particle also carries ApoB. Some labs report it with apolipoprotein A1.
Fasting has little effect on the result. The main source of variation is the assay: some labs report a mass concentration and others a molar concentration, and the two cannot be reliably converted into one another because the particle size differs between people. Results should be compared only within the same unit and method. Labs may print it as Lipoproteina (a).
Often read alongside: LDL cholesterol, Apolipoprotein B, Apolipoprotein A1, Total cholesterol, HDL cholesterol