title: Within-day biological variation and hour-to-hour reference change values for hematological parameters.
abstract: BACKGROUND
  Middle- and long-term biological variation data for hematological parameters have been reported in the literature. Within-day 24-h variability profiles for hematological parameters are currently lacking. However, comprehensive hour-to-hour variability data are critical to detect diurnal cyclical rhythms, and to take into account the 'time of sample collection' as a possible determinant of natural fluctuation. In this study, we assessed 24-h variation profiles for 20 hematological parameters.
  
  
  METHODS
  Blood samples were collected under standardized conditions from 24 subjects every hour for 24 h. At each measurement, 20 hematological parameters were determined in duplicate. Analytical variation (CVA), within-subject biological variation (CVI), between-subject biological variation (CVG), index of individuality (II), and reference change values (RCVs) were calculated. For the parameters with a diurnal rhythm, hour-to-hour RCVs were determined.
  
  
  RESULTS
  All parameters showed higher CVG than CVI. Highest CVG was found for eosinophils (46.6%; 95% CI, 34.9%-70.1%) and the lowest value was mean corpuscular hemoglobin concentration (MCHC) (3.2%; 95% CI, 2.4%-4.8%). CVI varied from 0.4% (95% CI, 0.32%-0.42%) to 20.9% (95% CI, 19.4%-22.6%) for red cell distribution width (RDW) and eosinophils, respectively. Six hematological parameters showed a diurnal rhythm.
  
  
  CONCLUSIONS
  We present complete 24-h variability profiles for 20 hematological parameters. Hour-to-hour reference changes values may help to better discriminate between random fluctuations and true changes in parameters with rhythmic diurnal oscillations.
authors.affiliation: .
authors.forename: Judith M
authors.initials: JM
authors.lastname: Hilderink
authors.affiliation: .
authors.forename: Lieke J J
authors.initials: LJJ
authors.lastname: Klinkenberg
authors.affiliation: .
authors.forename: Kristin M
authors.initials: KM
authors.lastname: Aakre
authors.affiliation: .
authors.forename: Norbert C J
authors.initials: NCJ
authors.lastname: de Wit
authors.affiliation: .
authors.forename: Yvonne M C
authors.initials: YMC
authors.lastname: Henskens
authors.affiliation: .
authors.forename: Noreen
authors.initials: N
authors.lastname: van der Linden
authors.affiliation: .
authors.forename: Otto
authors.initials: O
authors.lastname: Bekers
authors.affiliation: .
authors.forename: Roger J M W
authors.initials: RJMW
authors.lastname: Rennenberg
authors.affiliation: .
authors.forename: Richard P
authors.initials: RP
authors.lastname: Koopmans
authors.affiliation: .
authors.forename: Steven J R
authors.initials: SJR
authors.lastname: Meex
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002940:Circadian Rhythm; D005260:Female; D006403:Hematologic Tests / Q000592:standards*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture; D012016:Reference Values; D013048:Specimen Handling / Q000379:methods*
keywords: biological variation; diurnal rhythm; hematology; reference change value