Abstract
This study evaluated the effect of storage on the quantitation of lipoprotein (Lp)(a) in 25 serum samples. Aliquots of serum were stored for up to three years at either −20°C or−70°C and Lp(a) subsequently analyzed using an enzyme-linked immunosorbent assay kit. Concentrations of Lp(a) declined during storage, and the temperatures employed elicited significantly different (P<0.05) values within 12 mon which further diverged during three years of storage. Compared to baseline values, significant decreases (P<0.05) in Lp(a) levels were evident after six months of storage at−20°C with apparent losses (geometric mean) reaching 36.9% (95% confidence interval: 30.9%, 42.9%) after three years. Similarly, significantly lower (P<0.05) Lp(a) values were recorded after six months of storage at−70°C and at three years the decrease (geometric mean) was 19.1% (95% confidence interval: 14.3%, 24.0%). The losses, after three years, in terms of the arithmetic mean were 53.5 and 26.2% at−20 and−70°C, respectively. Phenotype analysis suggested that large isoforms are more susceptible to degradation than smaller moieties. This may be related to the observation that apparent losses are reduced in samples containing over 8 mg/dL Lp(a). Nevertheless, Lp(a) levels in stored samples retained a strong correlation with the baseline values. These results must be considered specific for the storage conditions and analytical procedures employed.
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Abbreviations
- Apo(a):
-
apolipoprotein(a)
- Lp(a):
-
lipoprotein(a)
- RID:
-
radial immunodifusion
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Evans, R.W., Sankey, S.S., Hauth, B.A. et al. Effect of sample storage on quantitation of lipoprotein (a) by an enzyme-linked immunosorbent assay. Lipids 31, 1197–1203 (1996). https://doi.org/10.1007/BF02524295
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DOI: https://doi.org/10.1007/BF02524295