Platelet Survival in Active Polycythaemia Vera with Reference to the Haematocrit Level

Platelet mean life span (MLS), platelet destruction rate, and platelet recovery was determined in 12 patients with active polycythaemia vera (PV), at a high‐haematocrit level and also after phlebotomies at a normal‐haematocrit level. The results have shown that (1) platelet MLS is not related to the haematocrit level, (2) platelet destruction rate, which equals production rate in the stationary state, in active PV far exceeds the range found in control subjects, (3) platelet production rate remains unchanged after phlebotomy, (4) platelet recovery, which gives an indirect estimation of the size of the exchangeable splenic‐platelet pool, is not affected by increased blood volume and red‐cell mass, but is affected by the size of the spleen.