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Homocysteine measurement by Vitros® Microtip homocysteine assay
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Geert A. Martens
Published/Copyright:
February 1, 2008
Abstract
Background: Elevated circulating total homocysteine is an independent vascular risk factor. Enzymatic homocysteine measurements represent an alternative to HPLC- or immunochemistry-based assays, suitable for automation. Here, we report on analytical performance of a commercial cystathionine β-synthase-based assay, for use on Vitros® automated analyzers.
Methods: Linear range, limit of detection and analytical sensitivity were inferred from duplicate measurements of homocystine standard solutions (1–65 μmol/L). Imprecision was assessed using commercial controls according to NCCLS EP5-A2 and accuracy using NIST-SRM1955 reference material. Agreement with a clinically validated HPLC method was examined on 207 patient samples.
Results: The enzymatic assay was linear from 1 to 90 μmol/L homocysteine. Total (within-day) imprecision ranged from 4.5 (3.9)% to 2.8 (1.6)% at homocysteine 9.7–43.2 μmol/L. Accuracy was acceptable at 8.9 and 17.7 μmol/L homocysteine, with +6.4% and –1.2% bias, respectively, but showed substantial negative bias (–20.1%) at 4.0 μmol/L. High triglycerides (19.8 μmol/L) negatively interfered. The enzymatic method was slightly less sensitive than the HPLC method (limit of detection 0.7 and 0.2 μmol/L, respectively) but correlated well with the latter (r2=0.9997, slope=1.04, intercept=–0.66 μmol/L) and was more precise (p<0.05).
Conclusions: The Vitros® homocysteine assay met the CLIA Desirable Analytical Quality Specifications at homocysteine ≥9 μmol/L. Its analytical performance and suitability for automation make the Vitros® assay an analytically acceptable alternative to HPLC-based methods.
Clin Chem Lab Med 2008;46:283–6.
Keywords: automation; cystathionine β-synthase; enzyme test; homocysteine; hyperhomocysteinemia; risk factor; vascular
Received: 2007-8-21
Accepted: 2007-10-19
Published Online: 2008-02-01
Published in Print: 2008-02-01
©2008 by Walter de Gruyter Berlin New York
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Keywords for this article
automation;
cystathionine β-synthase;
enzyme test;
homocysteine;
hyperhomocysteinemia;
risk factor;
vascular
Articles in the same Issue
- Opinion Papers
- The double whammy of endogenous insulin antibodies in non-diabetic subjects
- ‘Likelihood-ratio’ and ‘odds’ applied to monitoring of patients as a supplement to ‘reference change value’ (RCV)
- Genetics and Molecular Diagnostics
- A family with multiple mutations and sequence variations in the α- and β-globin gene clusters
- CTLA-4 polymorphism 49A–G is associated with placental abruption and preeclampsia in Finnish women
- Rare TA repeats in promoter TATA box of the UDP glucuronosyltranferase (UGT1A1) gene in Croatian subjects
- Association of high sensitive C-reactive protein with apolipoprotein E polymorphism in children and young adults: The Cardiovascular Risk in Young Finns Study
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