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KMID : 1101220030350010052
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2003 Volume.35 No. 1 p.52 ~ p.56
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Study of Homocysteine Assays on ADVIA Centaur; The Affects of Pre-analytical Sample Storage Conditions, and the Comparison of Results between EDTA Plasma and Serum Samples
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Lee Moo-Joo
Kim Young-Ha
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Abstract
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We studied Homocysteine assays on ADVIA Centaur (Bayer Co., USA) to evaluate the usefulness of the assay in the clinical laboratory. In this study we tested how pre-analytical sample storage conditions affect results and compared the differences of results between EDTA plasma and serum samples. We evaluated the usefulness of the Bayer Immunology reagents with the ADVIA Centaur autoanalyzer. Two clinical immunology items were analyzed in this study. EDTA plasma samples from 20 healthy subjects were assayed to set reference ranges of the method and commercialized bi-levels of QC materials (low: 7.2μ mol/L, high: 28.9 μmol/L). Two different concentrations of patient samples (24.7μmol/L and 40.0μmol/L) were used for within and between day precision tests of the assays. The 52 EDTA plasma sample results were used to review correlations with HPLC results. To see the affects of pre-analytical sample storage conditions, the samples of four healthy peoples were collected in EDTA and SST tubes then stored at 4℃ and 18℃ without centrifuging. Homocysteine concentrations were measured after 3 hours, 6 hours, 12 hours, and 24 hours following the collection for both EDTA and SST tube samples. CV values of within run, within day, and between day precision tests were 3.6-3.8%, 3.7-4.8% and 4.0-6.3% respectively. The results display a correlation with the HPLC method (r=0.9780). There is no clinical significance observed in the reference range of plasma and serum samples. The concentrations of homocysteine increased over time for the stored samples without centrifuge and the rate of increase in EDTA plasma is higher than in serum. The concentrations of EDTA plasma samples stored in room temperature without centrifuging are much higher than that of centrifuged EDTA plasma samples stored within 1 hour. The concentrations are 37%, in 3 hours, 50% in 6 hours, 100% in 12 hours, and 150% in 24 hours. This study shows that homocysteine assays on ADVIA Centaur has advantages in measuring concentrations faster and has acceptable precision and good correlations versus the HPLC method. Same reference ranges may be used for both EDTA plasma and serum samples if the serum is separated within one hour from collection. The concentration of homocysteine tends to increase by time after sample collection so it is highly recommended to separate the serum as soon as samples are collected.
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KEYWORD
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Homocysteine, HPLC, Precision, Lineality
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