ApoB/ApoA1 ratio calculator, with ApoB thresholds
ApoB counts the particles that can build plaque in your arteries. ApoA1 is the main protein on HDL, the particles that carry cholesterol away. The ApoB/ApoA1 ratio puts the two side by side, and in two large studies it predicted heart attacks better than the standard cholesterol numbers. Some labs print it. If yours prints only the two results, enter them below. Each can be in mg/dL or g/L.
The formula
ApoB/ApoA1 ratio = ApoB ÷ ApoA1
Both values must be in the same unit before dividing. That’s easy here, because 1 g/L is 100 mg/dL for both proteins, with no molar mass involved. An ApoB of 0.95 g/L is 95 mg/dL. The ratio itself has no unit, so it is the same number whether your lab reports in mg/dL or g/L.
An ApoB of 95 mg/dL with an ApoA1 of 140 mg/dL gives 95 ÷ 140 = 0.68. Lower is better: fewer plaque-forming particles for each HDL particle.
What the studies found
INTERHEART compared 15,152 people who had a first heart attack with 14,820 people who had not, in 52 countries. In the main 2004 paper, people in the top fifth of the ApoB/ApoA1 ratio had 3.25 times the odds of a heart attack of people in the bottom fifth. The authors estimated that 49% of heart attacks were attributable to a ratio above the bottom fifth, more than any other risk factor they measured.
A 2008 follow-up analysis by McQueen and colleagues compared the lipid measures directly. The ApoB/ApoA1 ratio had the highest attributable risk, 54%, and each standard deviation higher went with 1.59 times the odds of a heart attack. The total/HDL cholesterol ratio, the “cholesterol ratio” many reports print, came in at 32%, and the difference was statistically significant.
AMORIS followed 175,553 Swedish adults, most of them tested through routine health screening. In the 2001 paper by Walldius and colleagues, ApoB predicted fatal heart attacks better than LDL cholesterol in both men and women, and the authors suggested that ApoB, ApoA1, and the ratio be regarded as highly predictive of cardiac risk.
A 2021 AMORIS analysis followed 137,100 people from the same cohort for an average of 17.8 years. People in the top tenth of the ratio had 1.7 times the risk of a major cardiovascular event, and 2.7 times the risk of a nonfatal heart attack, of people in the bottom tenth. The ratio was already higher about 20 years before an event in the people who went on to have one.
Is there a cutoff?
No guideline sets a target for the ratio. The 2021 AMORIS paper proposed three tentative risk levels for men and women alike, which the calculator shows:
| Ratio | AMORIS 2021 risk level |
|---|---|
| 0.60 or below | Low |
| 0.61 to 0.90 | Medium |
| Above 0.90 | High |
The authors called these tentative and said cut values should be agreed in future guidelines. You may see other cutoffs quoted, including separate ones for men and women. Check where a cutoff comes from before reading much into it, and treat your ratio as a position on a scale where lower carries less risk.
ApoB on its own
The calculator also reads your ApoB against the thresholds used in How to track your ApoB over time:
| Source | ApoB (mg/dL) | ApoB (g/L) | What it means |
|---|---|---|---|
| 2018 AHA/ACC cholesterol guideline | 130 or above | 1.30 or above | A risk-enhancing factor |
| NLA 2024 consensus | 90, 70, 60 | 0.90, 0.70, 0.60 | Suggested thresholds for borderline to intermediate, high, and very high risk |
Which NLA threshold applies to you depends on your overall risk, which your clinician works out. ApoB is the half of the ratio that guidelines actually treat, so it is worth reading on its own even when the ratio looks fine.
Worked examples
| ApoB (mg/dL) | ApoA1 (mg/dL) | Ratio | AMORIS level |
|---|---|---|---|
| 80 | 160 | 0.50 | Low |
| 90 | 180 | 0.50 | Low |
| 90 | 100 | 0.90 | Medium |
| 95 | 140 | 0.68 | Medium |
| 120 | 115 | 1.04 | High |
The second and third rows have the same ApoB. A low ApoA1 alone is enough to move the ratio from the low band to the edge of the high one.
Limits
- A ratio hides which half moved. A ratio that rose because ApoB went up is a different story from one that rose because ApoA1 fell. Keep both results next to it.
- It is not a treatment target. Guidelines treat LDL, non-HDL, and ApoB. The ratio is context.
- Units must match. An ApoB in g/L divided by an ApoA1 in mg/dL gives a ratio a hundred times too small. The calculator converts each value, and flags one that looks like it’s in the other unit.
Tracking it over time
How to track your ApoB over time covers how much ApoB varies between draws, what moves it, and how to chart it next to LDL. The non-HDL cholesterol calculator works out the cholesterol in the same particles ApoB counts, from a standard lipid panel.
The ratio in HealthViewer
HealthViewer is a lab results tracker that runs on your own computer. It imports ApoB and other lipid results from lab report PDFs, MyChart downloads, and direct connections to your health system, and charts each test over time in Trends. Results in g/L are converted so they share a chart with results in mg/dL.
If your lab reports ApoA1 but not the ratio, you can create the ratio as a derived test in Settings: a formula of A ÷ B with ApoB and ApoA1 as the variables and no unit.
Everything stays in an encrypted file on your computer, with no account and no cloud service. Getting Started walks through the first import.
This calculator is for understanding your lab report, not for making treatment decisions. Ask your clinician what your numbers mean for you.