Calculates the LDL cholesterol-to-HDL cholesterol ratio.
Castelli Risk Index II: Clinical Guide
Browse Knowledge HubCalculates the LDL cholesterol-to-HDL cholesterol ratio. This clinical guide covers appropriate use, calculation, interpretation, limitations and practical safeguards.
Overview
Calculates the LDL cholesterol-to-HDL cholesterol ratio.
Clinical Significance
The LDL-to-HDL ratio is an adjunctive lipid index. Absolute LDL-C, non-HDL-C, apoB and total cardiovascular risk remain more directly actionable.
When to Use
- Describe the balance between LDL and HDL cholesterol.
- Use as a supplementary lipid measure rather than a standalone target.
- Interpret with the patient's complete cardiovascular-risk profile.
How It Is Calculated
- Castelli Risk Index II = LDL cholesterol ÷ HDL cholesterol.
- The calculator validates the required inputs before applying the equation and rounds only the displayed result.
Interpretation
- The LDL-to-HDL ratio is an adjunctive lipid index. Absolute LDL-C, non-HDL-C, apoB and total cardiovascular risk remain more directly actionable.
- Review the component values and assumptions as well as the final result.
Worked Example
Enter clinically plausible values in the stated units. MedicalC applies: Castelli Risk Index II = LDL cholesterol ÷ HDL cholesterol. Review the displayed result against the source data and the relevant clinical pathway.
Patient Considerations
- Confirm that the patient and clinical setting match the population or physiologic assumptions behind the equation.
- Consider whether treatment, organ function, pregnancy, body composition, sampling conditions or acute illness materially alter interpretation.
- Use serial calculations only when methods and units remain comparable.
Limitations
- The ratio does not capture triglyceride-rich lipoproteins.
- A favourable ratio can coexist with clinically important LDL elevation.
- Guideline targets are usually based on absolute lipid values and risk.
Clinical Pearls
- Confirm how LDL-C was obtained.
- Review LDL-C and HDL-C separately as well as the ratio.
- Use the same units for both values.
Common Mistakes
- Mixing units.
- Ignoring a high absolute LDL-C because the ratio seems acceptable.
- Using the ratio as a validated absolute-risk score.
Evidence Base
The implementation uses the published or established relationship: Castelli Risk Index II = LDL cholesterol ÷ HDL cholesterol. The cited source should be reviewed alongside current specialty guidance before clinical deployment.
Frequently Asked Questions
What does the Castelli Risk Index II calculator do?
Calculates the LDL cholesterol-to-HDL cholesterol ratio.
Can the result be used by itself?
No. The result is clinical decision support and must be interpreted with the source measurements, patient context and current guidance.
What most commonly makes the result unreliable?
Mixing units.
When should the calculation be repeated?
Repeat it when a relevant input, sampling condition, treatment or clinical state changes.
Does the calculator replace direct measurement or specialist review?
No. Use direct measurement, validated software or specialist review whenever the clinical decision requires greater precision.
References
- Castelli WP, et al. HDL cholesterol and other lipids in coronary heart disease. Circulation. 1977. — Primary publication, authoritative guideline or recognised clinical source supporting the calculation.
Reviewed by: MedicalC Clinical Editorial Team
Last reviewed: July 2026
Clinical Disclaimer
MedicalC calculators and clinical tools are intended to support healthcare professionals. They do not replace clinical judgement, individual patient assessment, local guidance or specialist advice.
Results should always be interpreted in the context of the patient’s history, examination, investigations, current clinical condition and applicable professional guidance.