Castelli Risk Index I: Clinical Guide

Overview

Calculates the total cholesterol-to-HDL cholesterol ratio.

Clinical Significance

The total cholesterol-to-HDL ratio summarises the balance between total and HDL cholesterol. It is an adjunct and should not replace validated absolute-risk assessment.

When to Use

• Summarise the relationship between total and HDL cholesterol.
• Use as a supplementary lipid measure.
• Interpret with absolute cardiovascular risk and current lipid guidance.

How It Is Calculated

• Castelli Risk Index I = total cholesterol ÷ HDL cholesterol.
• The calculator validates the required inputs before applying the equation and rounds only the displayed result.

Interpretation

• The total cholesterol-to-HDL ratio summarises the balance between total and HDL cholesterol. It is an adjunct and should not replace validated absolute-risk assessment.
• 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 I = total 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 can obscure high absolute LDL-C or non-HDL cholesterol.
• Treatment thresholds are not generally based on this ratio alone.
• Biological and laboratory variation affect both inputs.

Clinical Pearls

• The ratio is unitless when both values use the same unit.
• Review the component values, not only the ratio.
• Use guideline-based risk tools for treatment decisions.

Common Mistakes

• Mixing units.
• Assuming a favourable ratio cancels a markedly elevated LDL-C.
• Using the ratio as a sole treatment target.

Evidence Base

The implementation uses the published or established relationship: Castelli Risk Index I = total cholesterol ÷ HDL cholesterol. The cited source should be reviewed alongside current specialty guidance before clinical deployment.

References

1. 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.