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  • Practice Update from the CSCC Reference Interval Harmonization Working Group: Recommendations on LDL-C Calculation & Reporting

Practice Update from the CSCC Reference Interval Harmonization Working Group: Recommendations on LDL-C Calculation & Reporting

Sat, Jun, 2022 | eNews

Key Recommendation: All clinical laboratories in Canada should use the NIH LDL-equation to calculate and report LDL-C instead of the Friedewald LDL-C equation A toolbox has been created to aid in the implementation of the NIH LDL-C equation that consists of (1) a communication template to distribute to clinical users, (2) report comments to use when reporting LDL-C during the transition phase, and (3) a template to verify correct calculation by NIH LDL-C Equation.

Click here for the complete CSCC Harmonized Clinical Laboratory Lipid Reporting Recommendations.

NIH LDL-C equation Implementation toolkit:

Communication Template

Key Message

Effective [DATE], LDL-C will be reported as calculated by the NIH LDL-equation instead of the Friedewald LDL-C equation.

Current Friedewald LDL-C Equation (SI units)

New NIH LDL-C equation (SI units):

 

Background

  • Friedewald equation has traditionally been used to calculate LDL-C, was developed in 1972 and is not valid in patients who are non-fasting, have triglycerides >4.5 mmol/L or have type III hyperlipoproteinemia; it is inaccurate when LDL-C <1.5 mmol/L
  • NIH equation was developed in 2020 and validated in a Canadian population; it accurately estimates LDL-C when patients are non-fasting and when triglycerides are up to 9.0 mmol/L
  • NIH equation should not be used for patients with type III hyperlipoproteinemia and is inaccurate when LDL-C <0.5 mmol/L
  • NIH equation correlates well with Friedewald equation for most patients, but correlates better with β-quantification (LDL-C reference method) when triglycerides are high and LDL-C is low
  • Reporting LDL-C as calculated by the NIH equation is in accordance with the Harmonized Lipid Reporting Recommendations from the CSCC Harmonized Reference Interval Working Group (CSCC hRI-WG)

Why this is important:

  • The NIH equation provides a more accurate estimation than the Friedewald equation for LDL-C:
    • In the non-fasting state, which is becoming more common when ordering the lipid panel
    • When triglycerides are high (between 4.5 and 9.0 mmol/L), which is becoming more common with the increased prevalence of dyslipidemia
    • When LDL-C is low (between 0.5 – 1.5 mmol/L), which is becoming more common with more aggressive LDL-C targets

References:

  • Friedewald, et al. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clinical Chemistry 1972;18(6):499-502
  • Sampson M, et al. A new equation for calculation of low-density lipoprotein cholesterol in patients with normolipidemia and/or hypertriglyceridemia. JAMA Cardiology 2020;5(5):540-548
  • Higgins V, et al. Validating the NIH LDL-C equation in a specialized lipid cohort: Does it add up? Clinical Biochemistry. 2022;99:60-68
  • White-Al Habeeb N & Higgins V, et al. Harmonized Lipid Reporting for Clinical Laboratories based on the 2021 Canadian Lipid Guidelines. Canadian Journal of Cardiology. 2022;S0828-282X(22)00215-X

Transition Reporting Comments

The following comments can be considered, based on laboratory and IT resources. Depending on transition time, one or more comments may be appropriate.

Circumstance Comment
Prior to change, with unknown implementation date LDL-C result is based on the Friedewald LDL-C equation. The laboratory will be changing to the new NIH LDL-C equation that has improved accuracy when triglycerides are high and/or LDL-C is low.
Prior to change, with known implementation date LDL-C result is based on the Friedewald LDL-C equation. As of [DATE], the laboratory will change to the new NIH LDL-C equation that has improved accuracy when triglycerides are high and/or LDL-C is low.
After change LDL-C result is based on the NIH LDL-C equation.

Key verification conditions and template to verify correct calculation by NIH LDL-C Equation

Key Verification Conditions:

Condition Expected Result
LDL-C LoD of 0.50 mmol/L LDL-C results 0-0.49 mmol/L are reported as <0.50 mmol/L
Triglycerides >4.52 mmol/L LDL-C result is reported
Triglycerides >9.04 mmol/L LDL-C result is not reported. The comment “Unable to calculate“ is added to the report.
At least one component parameter not available LDL-C result is not reported. The comment “Unable to calculate“ is added to the report.

Template for testing:

Age (years) Sex Total Cholesterol (mmol/L) HDL-C (mmol/L) Triglycerides (mmol/L) NIH LDL-C Equation Calculation (mmol/L)
10 Male 2.30 0.60 5.20 <0.50
10 Female 2.30 0.60 5.20 <0.50
10 Male 3.90 0.60 5.00 1.55
10 Female 3.90 0.60 5.00 1.55
10 Male 7.10 0.70 1.00 6.00
10 Female 7.10 0.70 1.00 6.00
10 Male 4.20 0.50 10.2 Unable to calculate
10 Female 4.20 0.50 10.2 Unable to calculate
10 Male Not available 0.80 1.30 Unable to calculate
10 Female Not available 0.80 1.30 Unable to calculate
10 Male 3.90 Not available 1.30 Unable to calculate
10 Female 3.90 Not available 1.30 Unable to calculate
10 Male 3.90 0.80 Not available Unable to calculate
10 Female 3.90 0.80 Not available Unable to calculate
40 Male 2.30 0.60 5.20 <0.50
40 Female 2.30 0.60 5.20 <0.50
40 Male 3.90 0.60 5.00 1.55
40 Female 3.90 0.60 5.00 1.55
40 Male 7.10 0.70 1.00 6.00
40 Female 7.10 0.70 1.00 6.00
40 Male 4.20 0.50 10.2 Unable to calculate
40 Female 4.20 0.50 10.2 Unable to calculate
40 Male Not available 0.80 1.30 Unable to calculate
40 Female Not available 0.80 1.30 Unable to calculate
40 Male 3.90 Not available 1.30 Unable to calculate
40 Female 3.90 Not available 1.30 Unable to calculate
40 Male 3.90 0.80 Not available Unable to calculate
40 Female 3.90 0.80 Not available Unable to calculate

 

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