ApoB/ApoA1 ratio: what the blood test shows

The ApoB/ApoA1 ratio combines two separate protein tests into a single number. Apolipoprotein B is a protein found on the surface of every atherogenic lipoprotein particle — LDL, VLDL and IDL — so its amount directly shows how many such particles are in the blood, even if the amount of cholesterol they contain looks normal. Apolipoprotein A1, by contrast, is the main protein of HDL, the “good” cholesterol — it helps carry excess cholesterol from the tissues back to the liver, where it is removed. Because one marker reflects atherogenic and the other protective particles, their ratio is sometimes used as additional information alongside the whole lipid panel (total cholesterol, LDL, HDL, triglycerides) when lipid metabolism is being assessed. As with the separate ApoB and ApoA1 tests, MedlinePlus does not give a universal numeric limit for this ratio — the specific laboratory interval and its interpretation should be discussed with a doctor.

• When the number of atherogenic (LDL, VLDL) particles is to be assessed additionally, compared with the protective HDL protein, rather than only the separate amount of cholesterol
• Together with the whole lipid panel (total cholesterol, LDL, HDL, triglycerides), when the state of the cardiovascular system is being assessed
• When there is a family history of early heart disease, or LDL cholesterol stays high despite treatment
• When HDL cholesterol is low and a fuller picture of lipid metabolism is wanted
• When inherited disorders of lipid metabolism are suspected, such as familial hypercholesterolaemia or familial HDL deficiency

The MedlinePlus sources reviewed do not give a universal numeric range with units for the ApoB/ApoA1 ratio, in the same way as for the separate ApoB and ApoA1 tests. You will find the exact interval used by your laboratory on your own result report, and the specific interval and its interpretation should be discussed with a doctor. The ratio is treated as an additional marker alongside the usual lipid panel.

A raised ApoB/ApoA1 ratio indicates more atherogenic (LDL, VLDL) particles compared with the protective HDL protein. According to MedlinePlus, the causes that increase atherogenic particles include fatty food, excess weight, low physical activity, diabetes mellitus, kidney disease, a thyroid function disorder and inherited disorders of lipid metabolism; in addition, smoking lowers the HDL share, which also raises the ratio.

• Fatty food, excess weight, insufficient physical activity
• Diabetes mellitus, kidney disease, a thyroid function disorder (hypothyroidism), polycystic ovary syndrome
• Smoking — it does not increase cholesterol, but it lowers the HDL share
• Inherited disorders of lipid metabolism, for example familial hypercholesterolaemia
• Some medicines that affect lipid metabolism, for example contraceptive pills, diuretics or beta blockers (discuss the medicines you take with your doctor)
• Pregnancy and other states that increase the amount of female hormones

What to discuss with a doctor:

• The whole lipid panel (total cholesterol, LDL, HDL, triglycerides) for a more precise picture
• An assessment of the state of the cardiovascular system together with a doctor
• Family history of early heart disease
• Lifestyle factors — diet, physical activity, smoking, weight
• When to repeat the test to assess the change

A lowered ApoB/ApoA1 ratio

A lowered ApoB/ApoA1 ratio usually means fewer atherogenic (LDL, VLDL) particles compared with the HDL protein. According to MedlinePlus, the amount of ApoB is lowered by insufficient nutrition, by gastrointestinal diseases that interfere with fat absorption, or by liver function disorders, because ApoB-100 is produced in the liver; this can lower the ratio even if the HDL share does not change.

• Not enough fat or calories in the diet, or poor absorption of them
• Gastrointestinal diseases that interfere with fat absorption
• Liver function disorders, because ApoB-100 is produced in the liver
• Lipid-lowering treatment

What to discuss with a doctor:

• The whole lipid panel (total cholesterol, LDL, HDL, triglycerides) for an overall picture
• Liver markers and an assessment of nutrition
• Whether any lipid-lowering medicines are being taken that could affect the result
• When to repeat the test to assess the change