LDL Cholesterol Calculator (Sampson-NIH)
LDL Cholesterol Calculator (Sampson-NIH)
Estimate LDL cholesterol with the NIH equation 2 of Sampson and colleagues — derived against beta-quantification and usable up to a triglyceride of 800 mg/dL, where Friedewald stops at 400.
LDL Cholesterol (Sampson-NIH)
3 inputs → mg/dLTotal cholesterol 210 mg/dL, HDL 48 mg/dL, triglycerides 150 mg/dL
The Sampson-NIH equation (NIH equation 2)
All terms in mg/dL. non-HDL-C = TC − HDL-C.
- TG ÷ 8.56 + …
- the VLDL cholesterol term, which varies with the triglyceride and with non-HDL cholesterol instead of being a fixed fraction of the triglyceride
- − TG² ÷ 16100
- the quadratic term that stops the VLDL estimate rising indefinitely as triglycerides climb, which is what extends the usable range to 800 mg/dL
- mg/dL only
- the coefficients are fitted to mg/dL; convert a cholesterol in mmol/L by × 38.67 and a triglyceride by × 88.57 before entering it
- beta-quantification
- the ultracentrifugation reference method the equation was fitted and validated against
Worked example
Total cholesterol 210 mg/dL, HDL 48 mg/dL, triglycerides 150 mg/dL
Non-HDL cholesterol = 210 − 48 = 162 mg/dL
VLDL term = 150 ÷ 8.56 + 150 × 162 ÷ 2140 − 150² ÷ 16100 = 17.52 + 11.36 − 1.40 = 27.48 mg/dL
210 ÷ 0.948 − 48 ÷ 0.971 − 27.48 − 9.44 = 221.52 − 49.43 − 27.48 − 9.44 = 135.2 mg/dL
Friedewald on the same three values returns 132 mg/dL — the same sample, a different equation
LDL cholesterol categories in both units
| LDL-C (mg/dL) | LDL-C (mmol/L) | Category |
|---|---|---|
| < 100 | < 2.6 | Optimal |
| 100 – 129 | 2.6 – 3.3 | Near optimal / above optimal |
| 130 – 159 | 3.4 – 4.1 | Borderline high |
| 160 – 189 | 4.1 – 4.9 | High |
| ≥ 190 | ≥ 4.9 | Very high |
Sampson-NIH against Friedewald
| Friedewald | Sampson-NIH | |
|---|---|---|
| VLDL cholesterol term | Triglycerides ÷ 5, a fixed fraction | Varies with triglyceride and non-HDL, with a quadratic correction |
| Upper triglyceride limit | Invalid at ≥ 400 mg/dL | Validated to 800 mg/dL |
| Accuracy at LDL < 70 mg/dL | Under-estimates systematically | Closer to beta-quantification |
| Derivation standard | Ultracentrifugation, 1972 cohort | Beta-quantification, modern NIH cohort |
A better VLDL term, and what changes when a laboratory switches
The Sampson-NIH equation estimates LDL cholesterol from the same three measured values Friedewald uses — total cholesterol, HDL cholesterol and triglycerides — but replaces the fixed divisor of five with a VLDL cholesterol term that varies with both the triglyceride and the non-HDL cholesterol, plus a quadratic correction. It was derived and validated against beta-quantification, the ultracentrifugation reference method that physically separates lipoproteins by density before assaying the cholesterol in each fraction, rather than against another calculated result.
Two consequences follow. The equation remains usable to a triglyceride of 800 mg/dL, where Friedewald should not be reported above 400. And it is more accurate at low LDL concentrations and at higher triglycerides — which is precisely the population in whom treatment decisions are now made, since patients on statin, ezetimibe or PCSK9 therapy sit at LDL levels where Friedewald under-estimates systematically and a target can appear to have been reached when it has not.
Several large laboratories have changed the calculated LDL they report to this equation. The practical effect is that a patient’s LDL can appear to move between one report and the next with no biological change at all: the same total cholesterol, HDL and triglyceride, run through a different equation, give a different number. On the default values here the two equations differ by about 3 mg/dL, but the gap widens as triglycerides rise. Before acting on an apparent change in LDL, check whether the reporting method changed.
It remains a calculation and not a measurement. Above a triglyceride of 800 mg/dL it is outside its validated range and a direct LDL is required, and it is no more reliable than the three assays feeding it. The coefficients are fitted to mg/dL, so a report in mmol/L must be converted first — multiply cholesterol values by 38.67 and the triglyceride by 88.57, using the cholesterol and triglyceride converters. Where any doubt remains, non-HDL cholesterol needs no assumption about VLDL at all.
Frequently asked questions
What is the Sampson equation for LDL cholesterol?
It is NIH equation 2, published by Sampson and colleagues in 2020. It estimates LDL from total cholesterol, HDL and triglycerides, but models VLDL cholesterol as a function of both the triglyceride and non-HDL cholesterol rather than as a fixed fifth of the triglyceride.
Is Sampson-NIH more accurate than Friedewald?
It agrees more closely with beta-quantification at low LDL concentrations and at raised triglycerides, which is where Friedewald performs worst. At ordinary lipid levels the two give similar answers.
Why has my LDL changed when nothing else has?
Laboratories have been switching their reported calculated LDL from Friedewald to Sampson-NIH or Martin-Hopkins. The same total cholesterol, HDL and triglyceride run through a different equation give a different LDL, with no change in the patient.
Can I use this calculator with results in mmol/L?
Not directly — the coefficients are fitted to mg/dL. Convert first: multiply a cholesterol in mmol/L by 38.67 and a triglyceride in mmol/L by 88.57, then enter the mg/dL values.
What is the triglyceride limit for this equation?
It is validated to 800 mg/dL, twice the Friedewald limit of 400 mg/dL. Above 800 mg/dL a directly measured LDL should be requested instead.
Related calculators
References
- Sampson M, Ling C, Sun Q, et al. A new equation for calculation of low-density lipoprotein cholesterol in patients with normolipidemia and/or hypertriglyceridemia. JAMA Cardiol. 2020;5(5):540–548.
- Grundy SM, Stone NJ, Bailey AL, et al. 2018 AHA/ACC multisociety guideline on the management of blood cholesterol. Circulation. 2019;139(25):e1082–e1143.
- Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018.
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.