Effect of time on hematologic values in prediluted capillary and venous blood

Prediluted microsamples of capillary or venous blood are frequently stored for various amounts of time before determination of standard hematologic values. This study investigated changes in hematologic values during storage in Isoton II. No change in the erythrocyte count and the hemoglobin concentration was found for as long as four hours. However, a progressive decline in the leukocyte count and the mean corpuscular volume occurred during this period. For capillary samples the mean percentages of change in the leukocyte count and the mean corpuscular volume were -5% and -1.4%, respectively, after four hours. Similar changes were found for venous blood diluted in Isoton II. In addition, the platelet count of prediluted venous blood rose after four hours of storage, with a mean percentage of change of +2.5%. Changes in standard hematologic values may occur during storage of microsamples and may be of particular importance in pediatric hospitals, where large numbers of such samples are collected.