A noticeable error in indirect LDL estimation occurs when TAG exceeds what value?

• A. 100 mg/dL
• B. 200 mg/dL
• C. 300 mg/dL
• D. 400 mg/dL

Answer: (B)

The indirect LDL estimate uses the Friedewald equation, which assumes VLDL cholesterol is about one-fifth of the triglyceride level (VLDL-C ≈ TG/5) and that the sample is fasting with TG not too high. This simple relationship holds well at lower triglyceride levels, but as triglycerides rise beyond about 200 mg/dL, the actual relation between TG and VLDL-C shifts and the TG/5 approximation becomes less accurate. That mismatch makes the calculated LDL-C biased and the error becomes noticeable. So, the threshold where indirect LDL estimation starts to degrade noticeably is around 200 mg/dL of triglycerides.