Effect of sample aging on patient samples kept at ambient temperature before analysis with the Abbott Cell-Dyn 4000...

The effect of sample aging was studied on 80 blood samples collected from in-house patients within 2 hours before aspiration into the Cell-Dyn 4000 hematology analyzer. The first aspiration defined the zero-time value, and the samples were stored at ambient room temperature (23 degrees C) and reanalyzed at 12, 24, 48, 72, and 145 hours. Statistical analyses were made against the matched zero-time result for each patient. We report that the total white blood cell count is reliable for up to 24 hours, and that the 5-part differential count is reliable for up to 12 hours, being limited by the fragile eosinophils. This report shows that within 24 hours the neutrophil count, combined with the white cell count, is a more robust indicator of deviation of the main leukocyte subpopulation than the 5-part differential count. The platelet count was reliable for up to 12 hours. The erythrocyte mean cell volume (MCV) increased continuously during the observation period. In contrast, mean cell hemoglobin (MCH) showed a very small decrease after 72 hours. It is therefore proposed that MCH, and not MCV, should be used for diagnosis of the type of anemia.