Background: Since the clinical application of flow cytometry, many clinical laboratories have utilized this method for diagnosing hematologic malignancies. However, delays in testing can occur due to various reasons. To address this issue, whole blood fixatives are occasionally administered. Hence, this study aimed to determine the impact of applying whole blood fixative on bone marrow specimens.
Methods: Nine samples without lymphoma/leukemia bone marrow involvement were examined. Flow cytometry was performed using 17 common markers. The samples were stored at room temperature (RT) and 4°C without fixative treatment, stored at 4°C after TransFix (Cytomark, UK) treatment, and stored at RT after Cyto-Chex (Streck, USA) treatment. Subsequently, the samples were divided into groups and examined. A total of 13 tests were conducted on each sample for up to 5 days.
Results: The neutrophil and monocyte fractions improved when the samples were stored at 4°C, while no significant difference was observed in the lymphocyte fractions. The fluorescence intensity of the markers varied depending on the marker and conditions, with the most stable markers observed when stored in TransFix at 4°C, followed by storage at 4°C, CytoChex RT, and RT.
Conclusions: The use of fixative on bone marrow specimens maintained the stability of markers during delayed testing. Both fixatives are more effective in preserving marker intensity and cell fractions compared with RT storage. Refrigeration and the use of fixatives may be beneficial for examinations delayed beyond 72 hours.

Keywords: Flow cytometry, Fixatives, Preservative, Bone marrow, Stability