title: Differential reactivity of two homogeneous LDL-cholesterol methods to LDL and VLDL subfractions, as demonstrated by ultracentrifugation and HPLC.
abstract: BACKGROUND
  The analytical and clinical performance of homogeneous LDL-cholesterol assays has been reported, but their reactions with subfractions of LDL and VLDL have not been described in detail.
  
  
  METHODS
  We evaluated reaction selectivity of two homogeneous LDL-cholesterol assays, LDLk (Kyowa Medex) and LDLd (Daiichi Pure Chemical), with ultracentrifugally isolated VLDL and LDL subfractions to identify the lipoprotein particles from which the cholesterol recognized by these assays originates.
  
  
  RESULTS
  The LDLd (y) and LDLk (x) methods correlated highly for whole serum samples: y = 0.986x - 39.5 mg/L (r = 0.966; n = 34). In isolated VLDL, the LDLk and the LDLd methods recovered 17.3% and 23.8% of cholesterol, respectively; but correlation analysis revealed differential reactivity to small and large VLDL particles. For the isolated LDL subfraction of density 1.019-1.040 kg/L, the LDLd method had significantly higher reactivity (95.6-98.7%) than the LDLk (88.4-92.0%). Both methods, however, demonstrated poor recovery (approximately 50%) for the 1.050-1.063 kg/L fraction, indicating incomplete reactivity with small, dense LDL. Reactivity with lipoprotein(a) was better (71.2-90.8%) for both methods than with small LDL. For intermediate-density lipoprotein (IDL), there was no significant difference in recovery between the two methods (71.7% for LDLk and 68.9% for LDLd), but the LDLk method appeared to be more sensitive to IDL particle size.
  
  
  CONCLUSIONS
  The two homogeneous assays for LDL-cholesterol demonstrate only partial reactivity to small, dense LDL and nonspecific reactions to VLDL particles. Modification will be required in the homogeneous methods to obtain LDL-cholesterol values equivalent to those obtained by ultracentrifugation.
authors.affiliation: Faculty of Health Sciences, Okayama University Medical School, 2-5-1 Shikata-cho, Okayama-shi, Okayama 700-8558, Japan.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Usui
authors.forename: Hajime
authors.initials: H
authors.lastname: Kakuuchi
authors.forename: Motoi
authors.initials: M
authors.lastname: Okamoto
authors.forename: Yuki
authors.initials: Y
authors.lastname: Mizukami
authors.forename: Mitsuyo
authors.initials: M
authors.lastname: Okazaki
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D008078:Cholesterol, LDL / Q000097:blood*; D015243:Cholesterol, VLDL / Q000097:blood*; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D006949:Hyperlipidemias / Q000097:blood; D008875:Middle Aged; D011933:Reagent Kits, Diagnostic; D014461:Ultracentrifugation
chemical_list: D008078:Cholesterol, LDL; D015243:Cholesterol, VLDL; D011933:Reagent Kits, Diagnostic