Seasonal Variation in Hematocrit Value of Whole Blood

(Summary)We investigated seasonal variation of blood hematocrit value. Samples of whole blood (WB) at specific gravity of 1.052 were collected over the course of a year from healthy volunteers, and citrate-phosphate-dextrose solution (CPD solution) was used as anticoagulant solution. Hematocrit value was higher (mean, 36%) from November to March than that from June to October (mean, 34%). This variation was correlated with that of platelet rich plasma (PRP) volume obtained after centrifugation at 3.00×105 g-sec used in the preparation of blood component products. Thus, values for volume of PRP and ratio of PRP/WB varied inversely with hematocrit value over the course of the year. This seasonal variation of hematocrit value was presumed to be the source of the erythrocyte volume change associated with variation of plasma protein concentration and relative number of erythrocytes.