title: Evaluation of different formulas for LDL-C calculation.
abstract: BACKGROUND
  Friedewald's formula for the estimation of LDL-C concentration is the most often used formula in clinical practice. A recent formula by Anandaraja and colleagues for LDL-C estimation still needs to be evaluated before it is extensively applied in diagnosis. In the present study we validated existing formulas and derived a more accurate formula to determine LDL-C in a Serbian population.
  
  
  METHODS
  Our study included 2053 patients with TG < or = 4.52 mmol/L. In an initial group of 1010 patients, Friedewald's and Anandaraja's formulas were compared to a direct homogenous method for LDL-C determination. The obtained results allowed us to modify Friedewald's formula and apply it in a second group of patients.
  
  
  RESULTS
  The mean LDL-C concentrations were 3.9 +/- 1.09 mmol/L, 3.63 +/- 1.06 mmol/L and 3.72 +/- 1.04 mmol/L measured by a direct homogenous assay (D-LDL-C), calculated by Friedewald's formula (F-LDL-C) and calculated by Anandaraja's formula (A-LDL-C), respectively in the 1010 patients. The Student's paired t-test showed that D-LDL-C values were significantly higher than F-LDL-C and A-LDL-C values (p < 0.001). The Passing-Bablok regression analysis indicated good correlation between calculated and measured LDL-Cs (r > 0.89). Using lipoprotein values from the initial group we modified Friedewald's formula by replacing the term 2.2 with 3. The new modified formula for LDL-C estimation (S-LDL-C) showed no statistically significant difference compared to D-LDL-C. The absolute bias between these two methods was -0.06 +/- 0.37 mmol/L with a high correlation coefficient (r = 0.96).
  
  
  CONCLUSIONS
  Our modified formula for LDL-C estimation appears to be more accurate than both Friedewald's and Anandaraja's formulas when applied to a Serbian population.
authors.affiliation: Institute of Medical Biochemistry, Faculty of Pharmacy, Belgrade, Serbia. avujovic@pharmacy.bg.ac.rs
authors.forename: Ana
authors.initials: A
authors.lastname: Vujovic
authors.forename: Jelena
authors.initials: J
authors.lastname: Kotur-Stevuljevic
authors.forename: Slavica
authors.initials: S
authors.lastname: Spasic
authors.forename: Nada
authors.initials: N
authors.lastname: Bujisic
authors.forename: Jelena
authors.initials: J
authors.lastname: Martinovic
authors.forename: Milica
authors.initials: M
authors.lastname: Vujovic
authors.forename: Vesna
authors.initials: V
authors.lastname: Spasojevic-Kalimanovska
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Zeljkovic
authors.forename: Dragoljub
authors.initials: D
authors.lastname: Pajic
mesh_terms: D000328:Adult; D008078:Cholesterol, LDL / Q000032:analysis*; D019411:Clinical Laboratory Techniques; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D006937:Hypercholesterolemia / Q000097:blood* / Q000175:diagnosis*; D008055:Lipids / Q000737:chemistry; D008074:Lipoproteins / Q000737:chemistry; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D015203:Reproducibility of Results; D055771:Serbia
chemical_list: D008078:Cholesterol, LDL; D008055:Lipids; D008074:Lipoproteins