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 (CV Results: All parameters showed higher CV 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.