title: Biological variation and reference change values of common clinical chemistry and haematologic laboratory analytes in the elderly population.
abstract: BACKGROUND
  Biological variation (BV) and reference change values (RCVs) have been widely described for the general population, but the use of these data derived from adults in the elderly population is a controversial issue. We determined the within- and between-subject BV and RCV in both elderly and young people and compared them with previously published analyses.
  
  
  METHODS
  Samples were collected from 135 volunteers over 80 years of age at weekly intervals over 4 weeks. Eighteen biochemical and eight haematological analytes were measured. The Fraser and Harris methods were used to calculate the components of BV and RCV. To perform a comparative analysis, a reference group of 118 young subjects was studied under the same conditions.
  
  
  RESULTS
  The obtained coefficients of BV showed statistical differences in many cases, but in general, both the elderly and young patient data fall within the ranges previously described for the general population. The indexes of individuality for the analytes investigated did not exceed 1.4 in any case and were <0.6 for some analytes. The RCVs derived from elderly subjects were similar to those published in the young population, both in healthy and diseased individuals.
  
  
  CONCLUSIONS
  The strong individuality observed supports the preferential use of RCVs rather than population-based reference intervals in elderly people. For most of the analytes studied, data from the young population can be applied to elderly people, but the specific elderly coefficients of BV and RCVs are a recommended option.
authors.affiliation: Clinical Analysis Service, Hospital Virgen de la Salud, Toledo Hospital Complex, Avenida de Barber s/n, CP:45004, Toledo, Spain. dpinedatenor@gmail.com
authors.forename: Daniel
authors.initials: D
authors.lastname: Pineda-Tenor
authors.forename: Emilio José
authors.initials: EJ
authors.lastname: Laserna-Mendieta
authors.forename: Jesús
authors.initials: J
authors.lastname: Timón-Zapata
authors.forename: Laura
authors.initials: L
authors.lastname: Rodelgo-Jiménez
authors.forename: Raquel
authors.initials: R
authors.lastname: Ramos-Corral
authors.forename: Antonio
authors.initials: A
authors.lastname: Recio-Montealegre
authors.forename: Manuel Gómez-Serranillos
authors.initials: MG
authors.lastname: Reus
mesh_terms: D000328:Adult; D000367:Age Factors; D000369:Aged, 80 and over; D001773:Blood Cells / Q000166:cytology / Q000378:metabolism; D001774:Blood Chemical Analysis / Q000592:standards*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012737:Sex Factors; D055815:Young Adult