Flow Cytometric Enumeration of Peripheral Blood CD34⁺ Cells Predicts Bone Marrow Pathology in Patients with Less Than...

Significance of absolute number of CD34⁺ cells in the peripheral blood of patients with less than 1% myeloblasts by manual differential count is unknown and our aim is to study its relevance in clinical practice.

We studied 138 peripheral bloods flow cytometric analyses in patients with less than 1% myeloblasts by manual differential, when CD34⁺ events were present in the gate that encompassed lymphocytes, monocytes, stem cells, and blasts.

The average absolute number of CD34⁺cells in the peripheral blood was 11 CD34⁺cells/µL ranging from less than 1 cell/µL to 147 cells/µL. The average absolute number of CD34⁺ cells in patients with an abnormal expansive process involving bone marrow (metastases, myelodysplasia, granulomas, marrow infections) or if bone marrow biopsy not performed, presumed expansive marrow process was 25 cells/µL, and in patients without an expansive marrow process (or presumed negative) was 4 cells/µL (P<0.00007). Cutoff 12 CD34⁺ cells/μL had 93% positive predictive value for bone marrow involvement by an expansive process and 78% negative predictive value.

Flow cytometric testing of the peripheral blood is extremely sensitive method for enumerating CD34⁺ cells and can detect fewer than one CD34⁺ cell/µL. The absolute number of CD34⁺ cells in the peripheral blood is a useful parameter in determining marrow involvement by an expansive process and may provide guidance with respect to the necessity for bone marrow biopsy.