OBJECTIVETo investigate the growth of endogenous erythroid colony (EEC) in polycythemia vera (PV) patients and its clinical significance.

METHODSBone marrow mononuclear cells of 26 PV patients, 2 secondary erythrocytosis (SE) and 19 normal controls were cultured by Marsh's method for EEC.

RESULTS1. EEC was present in 25/26 (96.2%) PV patients and was not found in 2 SE patients and 19 normal controls. 2. The number of EEC and the ratio of EEC/Epo-dependent CFU-E (EEC ratio) were positively correlated with the hemoglobin (Hb) levels (r = 0.608, P = 0.01) in PV patients, but did not correlate with white blood cell (WBC) counts, platelet counts and neutrophil alkaline phosphatase scores. 3. EEC did not correlate with PV patients' serum Epo levels (r = 0.518, P = 0.125). 4. Fifteen PV patients were treated with hydroxyurea and/or interferon-alpha. Their EEC ratio before treatment was correlated positively with the time required for complete remission (CR) (r = 0.651, P = 0.009) and negatively with the time before relapsing (r = -0.529, P < 0.02). 5. EECs of 7 PV patients treated with HU/IFN were decreased after their blood cell counts normalization. 6. There was a positive correlation between the EEC ratio and the attacks of vascular thrombosis (r = 0.524, P = 0.01). (7) The apoptosis of bone marrow mononuclear cells of PV patients was less than that of normal controls. PV patients' EEC was negatively correlated with the apoptosis of their bone marrow mononuclear cells (r = -0.192, P < 0.045).

CONCLUSIONEEC is peculiarly present in PV patients, and is a sensitive parameter in reflecting the abnormal hematopoietic clone burden and in diagnosing and monitoring the disease.