Effects of anticoagulants on lipoprotein(a) measurements with four commercial assays.

Lipoprotein(a) levels in plasma are considered an independent risk factor for atherosclerosis at different sites. Although Lp(a) measurements have recently gained interest in clinical laboratories, several problems are still unresolved. A potential source of pre-analytical variability lies in the treatment of the specimens, since it has been reported that values of several lipid quantities are lower when measured in plasma instead of serum. Lp(a) was measured in serum and in EDTA-treated, heparinised and citrated plasma from 15 healthy volunteers. Four analytical methods were used: two enzyme linked immunosorbent assays [ELISA] based on a polyclonal anti-apolipoprotein(a) antibody and a polyclonal anti-apolipoprotein B antibody, respectively; and two immunonephelo-metric assays [INA] based on a N antiserum to Lp(a) and on three monoclonal antibodies adsorbed on latex particles, respectively. Our measured Lp(a) values in plasma were lower than those found in serum, in particular for EDTA-treated (anti-apolipoprotein(a) ELISA: p < 0.01, anti-apolipoprotein B ELISA: p < 0.001 and Latex enhanced INA: p < 0.001) and citrated plasma (anti-apolipoprotein(a) ELISA: p < 0.05, anti-apolipoprotein B ELISA: p < 0.001 and INA: p < 0.001). Lp(a) values measured in heparinised plasma were also lower than those found in serum, but the difference was not statistically significant.