The differential diagnosis of polycythaemia--a bone marrow study (the bone marrow in polycythaemia).

Bone marrow sections from posterior iliac crest aspiration and/or trephine specimens have been examined in 39 patients with true polycythaemia, along with a variety of other clinical and laboratory data. The emphasis has been on objective assessment of cellularity and megakaryocyte concentration in a prospective four year study. In patients with untreated primary polycythaemia mean cellularity was 87.0% and 86.4% for aspirate and trephine specimens compared with 55.5% and 48.7% for secondary cases and 48.3% and 45.5% for controls. Eighty per cent of primary polycythemia patients had moderate to marked megakaryocytic hyperplasia. We conclude that, in the presence of an elevated red cell volume, marrow cellularity of greater than 75%, particularly when accompanied by megakaryocytic hyperplasia, of iliac crest aspirate or trephine specimens is sufficient per se to establish a diagnosis of polycythaemia rubra vera.