Intraindividual variability in serum micronutrients: effects on reliability of estimated parameters.
Epidemiology
; 20(1): 36-43, 2009 Jan.
Article
em En
| MEDLINE
| ID: mdl-18813024
ABSTRACT
BACKGROUND:
Although serum measures of micronutrients are more specific than questionnaires in quantifying nutritional status, the reliability of serum measures depends on between- and within-person variability of circulating micronutrient levels. The extent to which multiple samples per person might improve reliability is useful information for planning studies and interpreting results.METHODS:
We analyzed levels of 25 micronutrients in serum samples taken from 381 Hawaii women at 4-month intervals. For all subjects and for subjects at the low and high end of the micronutrient distributions, we calculated inter- and intraindividual variability, reliability coefficients, and the number of measurements required to limit attenuation in estimated parameters (ie, to keep estimates close to their true values).RESULTS:
For 18 of the 25 micronutrients, a single measurement provided an estimate within 20% of the true value. For regression coefficients, 2 measurements were needed to limit attenuation to no more than 20% for nearly half of the micronutrients. To achieve no more than 10% attenuation, the number of measurements required ranged from 2 to 10 for correlation and from 3 to 20 for regression coefficients. To achieve no more than 5% attenuation, the corresponding ranges were 3 to 21 for correlation and 6 to 42 regression coefficients. In general, more measurements were required for adequate characterization of subjects with relatively high levels of micronutrients than for subjects with lower levels.CONCLUSIONS:
Our analysis suggests that 2 or 3 blood measurements are enough to limit attenuation of regression coefficients within 20% of the true value for most carotenoids and tocopherols. For 10% attenuation or less, 4 or more micronutrient measurements may be needed.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Estado Nutricional
/
Micronutrientes
Tipo de estudo:
Prognostic_studies
/
Risk_factors_studies
Limite:
Adolescent
/
Adult
/
Aged
/
Female
/
Humans
/
Middle aged
País/Região como assunto:
America do norte
Idioma:
En
Revista:
Epidemiology
Assunto da revista:
EPIDEMIOLOGIA
Ano de publicação:
2009
Tipo de documento:
Article
País de afiliação:
Estados Unidos