Guidance for storing blood samples in laboratories performing complete blood count with differential

The complete blood count (CBC) with differential leukocyte count (DIFF) is an important part of clinical laboratory analyses and provides crucial data for clinicians. Delivery time after blood collection and conditions of storage is known to affect the reliability of results of some hematologic parameters. The aim of this study was to assess the variations of hematologic parameters over time and the influence of storage temperature.

Blood samples were randomly selected from hospitalized patients and stored at room temperature and at 4 °C. CBC and DIFF were performed on an automated hematology analyzer and the results between the two groups were compared.

Samples stored at room temperature showed an important increase in mean corpuscular volume and hematocrit and a decrease in mean corpuscular hemoglobin concentration. Neutrophil counts tended to increase, whereas monocyte counts tended to decrease.

Storing samples at 4 °C improved reproducibility over time of all quantitative and qualitative parameters. We also observed that NEUT-X, a routine parameter useful in detecting myelodysplastic syndrome, became unreliable when analyzed 24 h after sample collection. Our results led us to recommend that samples should be analyzed within 6 h, particularly if samples are transported at room temperature. We also recommend storing samples at 4 °C in case of remote CBC analysis, especially in the context of clinical trials.