Effect of sample storage on the assay of lipoprotein(a) by commercially available radial immunodiffusion and enzyme-linked immunosorbent assay kits.
Lipoprotein(a) [Lp(a)] was measured by both a radial immunodiffusion (RID) kit from Immuno AG (Zurich, Switzerland) and a Tint Elize enzyme-linked immunosorbent assay (ELISA) kit from CytRx Biopool Ltd. (Umeå, Sweden) in serum samples that had been stored at -20 and -70 degrees C for six months. Storage temperature had no significant effect on the Lp(a) concentrations obtained by either method. After six months, mean Lp(a) degradation was 46% (95% confidence interval, 34-58%) with the RID kit; the ELISA data could not be compared between time points. In fresh sera, Lp(a) concentrations obtained by RID were 41% higher than by ELISA (because of differences in assay calibration materials), but in paired measurements of a set of 215 samples stored at -40 degrees C for an average of 10 years, Lp(a) concentrations were 62% lower by RID. This suggests that RID is more sensitive to the effects of long-term storage than is ELISA.
Craig
W Y
WY
Foundation for Blood Research, Scarborough, ME 04070-0190.
Poulin
S E
SE
Forster
N R
NR
Neveux
L M
LM
Wald
N J
NJ
Ledue
T B
TB
D004355:Drug Stability; D004797:Enzyme-Linked Immunosorbent Assay; D005188:False Negative Reactions; D006801:Humans; D005779:Immunodiffusion; D017270:Lipoprotein(a); D008074:Lipoproteins / Q000097:blood*; D011786:Quality Control; D011933:Reagent Kits, Diagnostic; D013696:Temperature; D013997:Time Factors
D017270:Lipoprotein(a); D008074:Lipoproteins; D011933:Reagent Kits, Diagnostic