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An approach to estimate between- and within-group correlation coefficients in multicenter studies: plasma carotenoids as biomarkers of intake of fruits and vegetables.
Am J Epidemiol 2005; 162(6):591-8AJ

Abstract

In a multicenter study, the overall correlation between two variables can be broken down into a within- and a between-group correlation reflecting associations at the individual and aggregate levels, respectively. A random-effects model is used to estimate variance components of nutrition-related variables and the within- and between-group correlation coefficients. Using data from the European Prospective Investigation into Cancer and Nutrition (EPIC), the authors analyzed the association between levels of three plasma carotenoids (alpha-carotene, beta-cryptoxanthin, and lycopene) and dietary intake of three items (total fruits, carrots, and tomatoes), assessed through dietary questionnaire and single 24-hour dietary recall measurements, in a cross-sectional study involving 3,089 subjects from nine European countries. Intraclass correlation coefficients were 0.178 for alpha-carotene, 0.216 for beta-cryptoxanthin, and 0.299 for lycopene. The between-group correlation coefficients were higher than the within-group coefficients for all three carotenoids. For beta-cryptoxanthin and fruit intake, the between-group versus the within-group correlations were 0.78 and 0.26 for the dietary questionnaire and 0.85 and 0.19 for the 24-hour dietary recall. Results indicate that variability of exposure is driven mainly by the individual compared with the aggregate variation and that biomarker levels perform fairly accurately in discriminating population-level consumption of fruits and vegetables.

Authors+Show Affiliations

Unit of Nutrition and Cancer, International Agency for Research on Cancer, Lyon, France. Ferrari@iarc.frNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Multicenter Study

Language

eng

PubMed ID

16093290

Citation

Ferrari, Pietro, et al. "An Approach to Estimate Between- and Within-group Correlation Coefficients in Multicenter Studies: Plasma Carotenoids as Biomarkers of Intake of Fruits and Vegetables." American Journal of Epidemiology, vol. 162, no. 6, 2005, pp. 591-8.
Ferrari P, Al-Delaimy WK, Slimani N, et al. An approach to estimate between- and within-group correlation coefficients in multicenter studies: plasma carotenoids as biomarkers of intake of fruits and vegetables. Am J Epidemiol. 2005;162(6):591-8.
Ferrari, P., Al-Delaimy, W. K., Slimani, N., Boshuizen, H. C., Roddam, A., Orfanos, P., ... Riboli, E. (2005). An approach to estimate between- and within-group correlation coefficients in multicenter studies: plasma carotenoids as biomarkers of intake of fruits and vegetables. American Journal of Epidemiology, 162(6), pp. 591-8.
Ferrari P, et al. An Approach to Estimate Between- and Within-group Correlation Coefficients in Multicenter Studies: Plasma Carotenoids as Biomarkers of Intake of Fruits and Vegetables. Am J Epidemiol. 2005 Sep 15;162(6):591-8. PubMed PMID: 16093290.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - An approach to estimate between- and within-group correlation coefficients in multicenter studies: plasma carotenoids as biomarkers of intake of fruits and vegetables. AU - Ferrari,Pietro, AU - Al-Delaimy,Wael K, AU - Slimani,Nadia, AU - Boshuizen,Hendriek C, AU - Roddam,Andrew, AU - Orfanos,Philippos, AU - Skeie,Guri, AU - Rodríguez-Barranco,Miguel, AU - Thiebaut,Anne, AU - Johansson,Gerd, AU - Palli,Domenico, AU - Boeing,Heiner, AU - Overvad,Kim, AU - Riboli,Elio, Y1 - 2005/08/10/ PY - 2005/8/12/pubmed PY - 2005/10/21/medline PY - 2005/8/12/entrez SP - 591 EP - 8 JF - American journal of epidemiology JO - Am. J. Epidemiol. VL - 162 IS - 6 N2 - In a multicenter study, the overall correlation between two variables can be broken down into a within- and a between-group correlation reflecting associations at the individual and aggregate levels, respectively. A random-effects model is used to estimate variance components of nutrition-related variables and the within- and between-group correlation coefficients. Using data from the European Prospective Investigation into Cancer and Nutrition (EPIC), the authors analyzed the association between levels of three plasma carotenoids (alpha-carotene, beta-cryptoxanthin, and lycopene) and dietary intake of three items (total fruits, carrots, and tomatoes), assessed through dietary questionnaire and single 24-hour dietary recall measurements, in a cross-sectional study involving 3,089 subjects from nine European countries. Intraclass correlation coefficients were 0.178 for alpha-carotene, 0.216 for beta-cryptoxanthin, and 0.299 for lycopene. The between-group correlation coefficients were higher than the within-group coefficients for all three carotenoids. For beta-cryptoxanthin and fruit intake, the between-group versus the within-group correlations were 0.78 and 0.26 for the dietary questionnaire and 0.85 and 0.19 for the 24-hour dietary recall. Results indicate that variability of exposure is driven mainly by the individual compared with the aggregate variation and that biomarker levels perform fairly accurately in discriminating population-level consumption of fruits and vegetables. SN - 0002-9262 UR - https://www.unboundmedicine.com/medline/citation/16093290/An_approach_to_estimate_between__and_within_group_correlation_coefficients_in_multicenter_studies:_plasma_carotenoids_as_biomarkers_of_intake_of_fruits_and_vegetables_ L2 - https://academic.oup.com/aje/article-lookup/doi/10.1093/aje/kwi242 DB - PRIME DP - Unbound Medicine ER -