A new Lp(a) assay that is unaffected by apo(a) size polymorphism.
We developed sandwich ELISA methods in which anti-apo(a) kringle 4 type 5 through protease (K4 x 5-Pro) domain monoclonal antibody (clone: 203E2) is employed in each instance as the capture antibody and one of the three species of monoclonal antibody [Mab] (clones: 108B8, 202A9, 2B3) is used as the labeled antibody. Using serum containing apo(a) with 34 repeats of kringle 4 as the calibrator, a commercial kit using anti-Lp(a) polyclonal antibody (Pab) or anti-apo(a) Mab overestimated the Lp(a) concentration in samples containing apo(a) with more than 34 repeats of kringle 4 and underestimated the Lp(a) concentration in samples containing apo(a) with fewer than 34 repeats of kringle 4. Moreover, it was demonstrated that the ratios of commercial kit values to anti-apo(a) K4 x 5-Pro Mab-based method values increased as the size of apo(a) increased. The ratios of apo(a) K5 x Pro Mab-based method values to anti-apo(a) K4 x 5-Pro Mab-based method values, however, remained almost constant regardless of the size polymorphism. Thus, we suggest that apo(a) size heterogeneity can significantly affect Lp(a) measurement in the Lp(a) assay using anti-Lp(a) Pab. The novel Lp(a) assay method, using only anti-apo(a) K4 x 5-Pro Mab, is not subject to this phenomenon.
Yamada
S
S
Central Institute, Shinotest Corporation, Sagamihara-shi, Kanagawa-ken, Japan.
Inoue
K
K
Morishita
R
R
Ogihara
T
T
Kubono
K
K
Kubo
N
N
Abe
A
A
Sakurabayashi
I
I
D000911:Antibodies, Monoclonal / Q000276:immunology; D001054:Apolipoproteins A / Q000737:chemistry / Q000235:genetics*; D002138:Calibration; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D006801:Humans; D017270:Lipoprotein(a) / Q000097:blood* / Q000276:immunology; D010316:Particle Size; D011110:Polymorphism, Genetic; D011994:Recombinant Proteins / Q000235:genetics; D012680:Sensitivity and Specificity
D000911:Antibodies, Monoclonal; D001054:Apolipoproteins A; D017270:Lipoprotein(a); D011994:Recombinant Proteins