title: Components of variation in serum carotenoid concentrations: the Polyp Prevention Trial.
abstract: OBJECTIVE
  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.
  
  
  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 beta-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 intra- to 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Laboratory of Biosystems and Cancer, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA. mforman@mdanderson.org
authors.forename: M R
authors.initials: MR
authors.lastname: Forman
authors.forename: C B
authors.initials: CB
authors.lastname: Borkowf
authors.forename: M M
authors.initials: MM
authors.lastname: Cantwell
authors.forename: S
authors.initials: S
authors.lastname: Steck
authors.forename: A
authors.initials: A
authors.lastname: Schatzkin
authors.forename: P S
authors.initials: PS
authors.lastname: Albert
authors.forename: E
authors.initials: E
authors.lastname: Lanza
mesh_terms: D000236:Adenoma / Q000097:blood / Q000517:prevention & control; D002338:Carotenoids / Q000097:blood*; D003110:Colonic Neoplasms / Q000097:blood / Q000517:prevention & control; D065366:Cryptoxanthins; D004032:Diet; D005260:Female; D006801:Humans; D014975:Lutein / Q000097:blood*; D000077276:Lycopene; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000517:prevention & control; D012307:Risk Factors; D012621:Seasons; D024341:Xanthophylls / Q000097:blood*; D065146:Zeaxanthins; D019207:beta Carotene / Q000097:blood*
chemical_list: D065366:Cryptoxanthins; D024341:Xanthophylls; D065146:Zeaxanthins; D019207:beta Carotene; D002338:Carotenoids; C041635:alpha-carotene; D000077276:Lycopene; D014975:Lutein