COMPONENTS OF BIOLOGICAL, INCLUDING SEASONAL, VARIATION IN HEMATOLOGICAL MEASUREMENTS AND PLASMA-FIBRINOGEN CONCENTRATIONS IN NORMAL HUMANS

This study has been carried out in order to examine the components of biological and, in particular, seasonal variation in hematologic measu rements in normal humans. Toward this end, 26 normal volunteers had mo nthly blood samplings during one calendar year for determination of nu mber of red blood cells (RBC) and platelets, hemoglobin (Hb), hematocr it (Ht),mean corpuscular volume (MCV), MC Hb (MCH), MC Hb concentratio n (MCHC), RBC distribution width (RDW), mean platelet volume (MPV), pl atelet distribution width (PDW), plateletcrit (PCT), and plasma fibrin ogen concentrations. The data were analyzed by means of spectral analy ses of a group of time series or a single time series, and by means of repeated measures analyses of variance. Most of the hematologic varia bles show seasonal rhythms, such as annual rhythms or harmonics, which are expressed as a group phenomenon. An important part of the varianc e (> 15%) in Ht, MCV, MCH, MCHC, RDW, number of platelets, MPV and pla sma fibrinogen was explained by a yearly variation. The peak-trough di fferences (expressed as a percentage of the mean) in the yearly variat ions in number of RBC, Ht, MCV, MCH, MCHC and RDW were very low (all < 8.5%). Number of platelets (14.4%) and plasma fibrinogen values (28%) showed a high-amplitude yearly variation. All hematological variables , except MCHC, show a high interindividual variability which exceeds b y far the intraindividual variability.