title: A modified formula for calculating low-density lipoprotein cholesterol values.
abstract: BACKGROUND
  The Friedewald formula (FF) is useful for calculating serum low-density lipoprotein cholesterol (LDL-C) values, but has a remarkable deviation and limitation especially in hypertriglyceridemia. We modify the formula which is now more suitable for LDL-C calculation.
  
  
  METHODS
  2180 cases were classified into three groups according to their TG concentrations (A: < 200 mg/dl, n = 1220; B: 200-400 mg/dl, n = 480; C: 400-1000 mg/dl, n = 480). The concentrations of LDL-C were measured or estimated by 1) a direct measurement (DM); 2) the FF; and 3) our modified Friedewald formula (MFF): LDL-C (mg/dl) = Non-HDL-C x 90% - TG x 10%.
  
  
  RESULTS
  Linear regression showed a significant correlation (P < 0.001) between the measured and calculated LDL-C values. Bland-Altman plots indicated that the methods (DM/MFF) were in better agreement than those (DM/FF). The LDL-C/Non-HDL-C ratio in FF calculated values was significantly lower (P < 0.05) than that in MFF or DM values, while no significant difference between MFF and DM was found. In Group A and Group B, 4.26% and 14.79% of the MFF calculated values had more than 20% deviation from those measured by DM. These percentages were significantly lower than those calculated by FF, where 7.30% and 25.63% were observed, respectively (P < 0.01 and P < 0.001). The MFF calculated values were all positive even in Group C.
  
  
  CONCLUSIONS
  Compared with the FF calculation, serum LDL-C values estimated by our modified formula are closer to those measured by a direct assay. The modification significantly diminishes the interference caused by hypertriglyceridemia.
authors.affiliation: Zhongshan Hospital, Fudan University, Shanghai, China.
authors.forename: Yunqin
authors.initials: Y
authors.lastname: Chen
authors.forename: Xiaojin
authors.initials: X
authors.lastname: Zhang
authors.forename: Baishen
authors.initials: B
authors.lastname: Pan
authors.forename: Xuejuan
authors.initials: X
authors.lastname: Jin
authors.forename: Haili
authors.initials: H
authors.lastname: Yao
authors.forename: Bin
authors.initials: B
authors.lastname: Chen
authors.forename: Yunzeng
authors.initials: Y
authors.lastname: Zou
authors.forename: Junbo
authors.initials: J
authors.lastname: Ge
authors.forename: Haozhu
authors.initials: H
authors.lastname: Chen
mesh_terms: D008078:Cholesterol, LDL / Q000097:blood*; D006801:Humans; D015228:Hypertriglyceridemia; D008962:Models, Theoretical; D014280:Triglycerides / Q000097:blood; D014894:Weights and Measures; D055815:Young Adult
chemical_list: D008078:Cholesterol, LDL; D014280:Triglycerides