Biological Variation of Vitamins in Blood of Healthy Individuals

Talwar, Dinesh; Azharuddin, Mohammed; Williamson, Cathy; Teoh, Yee Ping; McMillan, Donald C.; O’Reilly, Denis St. J.

doi:10.1373/clinchem.2005.056374

Cited by 40 publications

(34 citation statements)

References 28 publications

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“…Free plasma amino acids exhibit relatively low CV I values, similar to those reported for other diet related metabolites such as, plasma vitamins (29). The essential amino acids showed lower CV I than non-essential amino acids.…”

Section: Discussionsupporting

confidence: 75%

“…The RCVs were high for amino acids primarily due to their within-subject component of variation, a common finding in other diet-related metabolites studied in plasma (29). Therefore, relatively large differences between results of sequential samples would be required, i.e., a difference of 31% between two consecutive results in hyperphenylalaninemia monitoring would be necessary to indicate significant changes as a result of treatment.…”

Section: Discussionmentioning

confidence: 99%

“…The increasing interest in the application of biological variation data has prompted the study of several ''esoteric'' analytes, such as N-terminal pro-brain natriuretic peptide (28), blood vitamins (29) or asymmetric dimethylarginine (30). However, to our knowledge, no previous specifically designed studies on biological variation have been reported for free plasma amino acids.…”

Section: Discussionmentioning

confidence: 99%

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Biological variation of free plasma amino acids in healthy individuals

Corte

Venta²

2009

Clinical Chemistry and Laboratory Medicine

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Background: Biological variation data for free plasma amino acids are lacking from the more comprehensive databases. Therefore, we determined the intra-and inter-individual components of variation in healthy subjects. These data were used to define desirable goals for imprecision, bias and total error, indices of individuality and reference change values. Methods: Plasma samples were collected from 11 volunteers at weekly intervals over 5 weeks. Free plasma amino acids were analyzed by reversed-phase HPLC and analytical and biological variation data were derived using ANOVA. Results: Intra-individual coefficients of variation ranged from 9.5% to 46.4%, with lower values among the essential amino acids. The mean inter-individual coefficient of variation was 46.6% and was higher than intra-individual values for all amino acids. Thus, indices of individuality were below 0.8. Reference change values ranged from 30.9% to 128.4% and total error values ranged from 15.2% to 61.0%. Conclusions: Plasma amino acids exhibit relatively low intra-individual coefficients of variation, with essential amino acids showing tighter homeostatic control. Analytical quality goals can be reasonably achieved with current methods. Reference intervals are of limited value in the detection of unusual results in an individual. Therefore, comparison of serial results by means of the reference change values is recommended. Clin Chem Lab Med 2010;48:99-104.

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Section: Discussionsupporting

confidence: 75%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Biological variation of free plasma amino acids in healthy individuals

Corte

Venta²

2009

Clinical Chemistry and Laboratory Medicine

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“…Earlier research has reported intra-and interindividual variations in serum carotenoid concentrations in small samples (Tangney et al, 1987;Yong et al, 1994;Talwar et al, 2005), in smokers (Block et al, 2006) and in one large sample of the European Prospective Investigation of Cancer (EPIC) . Yet large-scale multicenter trials, such as the Polyp Prevention Trial (PPT; Appendix), or observational research like the EPIC, contribute additional sources of variation in serum carotenoid concentrations due to potential within-and between-center and seasonal differences in serum levels .…”

Section: Introductionmentioning

confidence: 99%

Components of variation in serum carotenoid concentrations: the Polyp Prevention Trial

et al. 2008

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Objectives: The intra-and interindividual variations and season and center effects were estimated from a series of serum carotenoid concentrations in the Polyp Prevention Trial (PPT) participants. Subjects/Methods: Fasting blood was collected annually for 4 years in all 1905 participants, and a subcohort of 901 participants were selected within each (of eight) center(s), by gender and dietary arm of the study, for measurement of five major carotenoid peaks. Using variance of component methods, the variation in serum carotenoid concentrations about the underlying mean was partitioned into explanatory components attributed to various sources. Results: The contributions of the inter-and intraindividual variances to the overall variation in carotenoid concentrations were in the range of 61-70 and 20-35%, respectively, whereas center and center-by-season effects provided 2.6-9.5 and 0.2-1.4%, respectively. The highest percent (35%) of intraindividual variation was exhibited by lycopene, and the highest percent (70% apiece) of interindividual variation was exhibited by lutein/zeaxanthin and b-carotene. Serum lycopene had the highest ratio of intra-to interindividual variation of 0.57, whereas lutein had the lowest ratio of 0.29. We estimate that the ratio of intrato interindividual variance around the mean carotenoid concentration can be reduced greatly by collecting 3-4 compared to 1 blood measurement in large-scale trials like the PPT. Conclusion: In the largest study of components of variation in individuals at high risk for colorectal cancer, the largest contributors to variation in serum carotenoid concentrations were intra-and interindividual effects followed by center and center-by-season effects.

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“…The limit of detection of our assay is 0.08 nmol/L, which is comparable to that reported by others (19 -22, 24, 33 ). The between-run imprecision of the assay is well below the reported desirable imprecision goal (CV 19%) based on biological variation of phylloquinone (36 ).…”

Section: 33 )mentioning

confidence: 77%

HPLC Method for Plasma Vitamin K1: Effect of Plasma Triglyceride and Acute-Phase Response on Circulating Concentrations

et al. 2007

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Background:The plasma concentration of vitamin K 1 (phylloquinone) is the most reliable index for assessing vitamin K status. Our aim was to analytically validate an HPLC method for quantifying phylloquinone in plasma and to examine the effect of plasma triglyceride concentration on the phylloquinone reference interval. We also examined the effect of acute-phase response on phylloquinone concentration in plasma. Methods: Phylloquinone was extracted from fasting plasma samples by deproteinization and C18 solidphase extraction, separated by reversed-phase HPLC, and detected fluorometrically after postcolumn reduction with a platinum catalyst. We synthesized a novel internal calibrator, docosyl naphthoate. Results: The recovery of phylloquinone was >90%. Between-run imprecision was 8.7%-9.0%, and withinrun imprecision was 3.8%-7.0%. The linearity was up to 44.8 nmol/L, limit of detection 0.08 nmol/L, and limit of quantification 0.14 nmol/L. The correlation between plasma phylloquinone and triglyceride concentrations was r ‫؍‬ 0.7 in the reference population. The 95% reference interval for the phylloquinone:triglyceride ratio was 0.20 to 2.20 nmol/mmol. Plasma concentrations of C-reactive protein were significantly increased, whereas triglyceride and phylloquinone but not the phylloquinone:triglyceride ratio were transiently decreased >50% after surgery.

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Biological Variation of Vitamins in Blood of Healthy Individuals

Cited by 40 publications

References 28 publications

Biological variation of free plasma amino acids in healthy individuals

Biological variation of free plasma amino acids in healthy individuals

Components of variation in serum carotenoid concentrations: the Polyp Prevention Trial

HPLC Method for Plasma Vitamin K1: Effect of Plasma Triglyceride and Acute-Phase Response on Circulating Concentrations

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