Statistical
Friedewald LDL-C estimate, non-HDL-C and TC/HDL: guarded spreadsheet examples
Calculate three different lipid-panel quantities with explicit mg/dL units, input checks and limits on the Friedewald estimate.
An estimate with limitations, not a lab replacement
Use fictional values in mg/dL throughout. Friedewald estimates LDL-C as total cholesterol minus HDL-C minus triglycerides/5. The divisor is unit-dependent: do not enter mmol/L in this example.
This exercise rejects triglycerides at or above 400 mg/dL. A value below that cutoff does not guarantee accuracy, particularly with low LDL-C or elevated triglycerides. Martin/Hopkins is another estimating equation, not an assay; selection of an appropriate lab method is outside this worksheet.
Non-HDL-C is total cholesterol minus HDL-C. It measures cholesterol content, not the number of apoB particles, and still depends on accurate lab measurements. TC/HDL is a separate dimensionless ratio. None of these outputs alone establishes a diagnosis or treatment.
Guarded Friedewald LDL Cholesterol in mg/dL (blocks TG >= 400)
Require positive total and HDL cholesterol, nonnegative triglycerides and HDL no greater than total. A negative unrounded estimate gets an explicit review message instead of being rounded or clamped to zero. These are elementary arithmetic checks, not validation of a specimen.
=IF(COUNT(B2:B4)<>3,"Invalid inputs",IF(OR(B2<=0,B3<=0,B4<0,B3>B2),"Invalid inputs",IF(B4>=400,"Outside Friedewald range",IF(B2-B3-B4/5<0,"Negative estimate: review inputs",ROUND(B2-B3-B4/5,1)))))Non-HDL cholesterol in mg/dL
Subtract two compatible measurements. This calculation does not use triglycerides, so it can still be evaluated when the separate Friedewald estimate is outside its stated range.
=IF(COUNT(B2:B3)<>2,"Invalid inputs",IF(OR(B2<=0,B3<=0,B3>B2),"Invalid inputs",B2-B3))Total-to-HDL ratio
Divide total cholesterol by positive HDL cholesterol. Zero or missing HDL is invalid, not a zero ratio.
=IF(COUNT(B2:B3)<>2,"Invalid inputs",IF(OR(B2<=0,B3<=0,B3>B2),"Invalid inputs",ROUND(B2/B3,2)))Try the example
Use the original values or change them to test your understanding.