ApoB/ApoA-1 Ratio Calculator
ApoB/ApoA-1 Ratio Calculator
Divide apolipoprotein B by apolipoprotein A-1 for the single most informative number the two tests produce — atherogenic particles against protective ones, on a non-fasting sample, with sex-specific thresholds.
ApoB/ApoA-1 ratio
ApoB ÷ ApoA-1, by sexApoB 1.05 g/L, apoA-1 1.35 g/L, male
Formula
Both in the same unit — g/L or mg/dL — because the units cancel
- units cancel
- unlike the triglyceride to HDL ratio, this one is genuinely dimensionless: both terms are protein mass concentrations converting by the same factor of 100, so g/L and mg/dL give an identical answer
- same sample, same method
- both apolipoproteins are measured immunoturbidimetrically on one specimen, so a systematic bias in the assay or in the specimen largely divides out of the ratio
- no fasting
- apolipoprotein concentrations are not appreciably affected by fasting status, which is why INTERHEART used non-fasting samples in all 52 countries
- sex thresholds
- 0.7 and 0.9 in men, 0.6 and 0.8 in women. The split reflects the higher apoA-1 distribution in women rather than a sex-specific outcome analysis
Worked example
ApoB 1.05 g/L, apoA-1 1.35 g/L, male
1.05 ÷ 1.35 = 0.78
Between 0.7 and 0.9 in a man — intermediate
The same numbers in mg/dL, 105 ÷ 135, give 0.78 as well: the units cancel
In a woman the same 0.78 would sit just under her high-risk threshold of 0.8 — the identical ratio, one band-width closer to the boundary
Neither reading is a decision. It is one input to a cardiovascular risk assessment made by a clinician
Thresholds, and where each number comes from
| Category | Men | Women | Source of the figure |
|---|---|---|---|
| Low risk | < 0.7 | < 0.6 | Below the AMORIS low-risk boundary of 0.6, which is sex-independent as published |
| Intermediate | 0.7 – 0.9 | 0.6 – 0.8 | The middle band in laboratory practice |
| High risk | > 0.9 | > 0.8 | 0.9 is the AMORIS high-risk boundary; 0.8 is the female upper reference limit in FINRISK 2007 |
| Population reference interval | 0.3 – 1.0 | 0.3 – 0.8 | FINRISK 2007, 2.5th to 97.5th centiles |
Why the ratio beats either apolipoprotein alone
| Property | What it buys you |
|---|---|
| Both measured on one sample by one method | A systematic bias — assay calibration, dilution, a lipaemic specimen — affects numerator and denominator together and largely divides out |
| Dimensionless | g/L and mg/dL give the same number, so a unit error cannot move a patient across a threshold |
| No fasting required | INTERHEART used non-fasting samples in 52 countries for exactly this reason; a calculated LDL cholesterol cannot make the same claim |
| Combines both directions of risk | The atherogenic particle count sits over the protective one, so the two components reinforce rather than dilute each other |
Atherogenic particles over protective ones, on one sample
The apoB/apoA-1 ratio puts the number of atherogenic particles over the amount of the main protective apolipoprotein, and it is the most informative single number the two tests produce. In INTERHEART, the 52-country case-control study of first myocardial infarction, the top quintile of this ratio carried an odds ratio of 3.25 with a population attributable risk of 49.2% — second among all nine risk factors examined, behind current smoking and ahead of hypertension, diabetes and obesity.
Three properties make it robust in a way neither apolipoprotein is alone. Both are measured on the same specimen by the same immunoturbidimetric method, so a systematic bias in the assay, the calibration or the sample largely divides out of the ratio. It is genuinely dimensionless: both terms are protein mass concentrations that convert between g/L and mg/dL by the same factor of 100, so entering both in either unit gives an identical answer. And apolipoprotein concentrations are not appreciably affected by fasting, which is why INTERHEART could use non-fasting samples across 52 countries and why a calculated LDL cholesterol cannot make the same claim.
The thresholds deserve to be stated honestly. Laboratories quote 0.9 in men and 0.8 in women as the high-risk boundary, with 0.7 and 0.6 as the low-risk one, and this calculator applies them. The 0.9 figure is the AMORIS high-risk boundary and the 0.8 figure is the upper reference limit for women in a population reference sample. But the AMORIS categories as published by their own authors are sex-independent and described as tentative, so the sex split comes from the reference intervals rather than from an analysis showing that the same ratio means something different in a woman.
What the ratio is not is a treatment target. No guideline has adopted a ratio threshold as a goal of therapy; the ESC/EAS secondary goals are stated for apoB alone. Its use is as one input to a cardiovascular risk assessment, alongside blood pressure, smoking, glycaemia, family history, lipoprotein(a) and a formal risk score. A high ratio should prompt a proper assessment rather than substitute for one, and a reassuring ratio does not cancel a strong family history or an established diagnosis of atherosclerotic disease.
Frequently asked questions
What is a good apoB/apoA-1 ratio?
Below about 0.7 in men and 0.6 in women is generally described as low risk; above about 0.9 in men and 0.8 in women as high risk, with the range between them intermediate. These are risk markers derived from cohort studies, not treatment targets.
Does it matter whether I enter g/L or mg/dL?
No, as long as both values use the same unit. Both apolipoproteins convert between g/L and mg/dL by the same factor of 100, so the units cancel and the ratio is identical. This is the opposite of the triglyceride to HDL ratio, where they do not cancel.
Why are the thresholds lower in women?
Because women run higher apoA-1 concentrations throughout adult life, so the same apoB gives a lower ratio. The split comes from the sex difference in the reference intervals; the AMORIS categories as published by their own authors are sex-independent.
Do I need to fast for this test?
No. Apolipoprotein concentrations are not appreciably affected by fasting status, which is why INTERHEART used non-fasting samples in all 52 countries. It is one of the practical advantages the ratio has over a calculated LDL cholesterol.
Should the ratio be used instead of LDL cholesterol?
Not instead of a full assessment. No guideline sets a ratio target, and the ESC/EAS secondary goals are stated for apoB alone. Treat a high ratio as a prompt to assess cardiovascular risk properly rather than as a decision in itself.
Related calculators
References
- Yusuf S, Hawken S, Ôunpuu S, et al. Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): case-control study. Lancet. 2004;364(9438):937–952.
- Walldius G, de Faire U, Alfredsson L, et al. Long-term risk of a major cardiovascular event by apoB, apoA-1, and the apoB/apoA-1 ratio — experience from the Swedish AMORIS cohort: a cohort study. PLoS Med. 2021;18(12):e1003853.
- McQueen MJ, Hawken S, Wang X, et al. Lipids, lipoproteins, and apolipoproteins as risk markers of myocardial infarction in 52 countries (the INTERHEART study): a case-control study. Lancet. 2008;372(9634):224–233.
- Leiviskä J, Sundvall J, Alfthan G, Jauhiainen M, Salomaa V. Apolipoprotein A-I, apolipoprotein B, and apolipoprotein B/apolipoprotein A-I ratio: reference intervals from the FINRISK 2007 study. Clin Chim Acta. 2011;412(11–12):1146–1150.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.