Flow cytometric evaluation of circulating CD34+ cell counts and apoptotic rate in children with acquired aplastic anemia and myelodysplasia

OBJECTIVE: Identification of a rapid and noninvasive test for the follow-up of aplastic anemia (AA) patients during immunosuppressive therapy (IST) to evaluate its functional effect on hematopoietic progenitors (HPC) and for early detection of progression to myelodysplasia or relapse. MATERIALS AND METHODS: Absolute count and apoptotic rate (AR) of peripheral blood (PB) CD34+ cells were evaluated by three-color flow cytometry for CD45, CD34, and annexin V in cord blood (CB), normal children, and adults, as well as in pediatric patients with AA at diagnosis and during IST, Fanconi anemia (FA), chronic immune cytopenia, and refractory anemia with excess blasts (RAEB). RESULTS: In normal subjects, the AR of PB CD34+ cells showed a progressive increase (p < 0.05), while their counts decreased (p < 0.05) from birth to adulthood. In very severe AA (vSAA) and severe AA (SAA) at diagnosis, the AR was 91.6% +/- 2.8%, higher than controls (p < 0.05), and PB CD34+ cell count was 2.6 +/- 2.4/microL. In FA patients, the PB CD34+ AR was again significantly increased (54.2% +/- 13.7%) with an absolute count of 3.7 +/- 1.2/microL. Conversely, in RAEB the AR was 11.7% +/- 3.5% and the absolute count 85.1 +/- 48.2/microL (p < 0.05). Chronic immune cytopenias did not significantly differ from controls. CONCLUSIONS: Flow cytometry evaluation of PB CD34+ AR and counts is a noninvasive and feasible first-step method for the differentiation of AA and myelodysplasia (MDS), and it might be useful for monitoring AA during IST to secure the early detection of relapse or transformation to MDS.