IDIOPATHIC ERYTHROCYTOSIS - ADDITIONAL NEW STUDY TECHNIQUES SUGGEST AHETEROGENOUS GROUP

25 patients with idiopathic erythrocytosis (absolute increase in red c ell mass without conventional criteria of primary polycythaemia or kno wn underlying cause) have been further studied for evidence of primary or secondary polycythaemia. Additional non-conventional criteria used were: platelet distribution width, platelet nucleotide ratio, serum e rythropoietin, clinical evidence of ischaemic vascular disease and ery throid culture variables in serum-free system. All had been used in an earlier study in score form to assist in the diagnosis of primary pol ycythaemia. These patients were also newly assessed for the presence o f hypoxia (supine oximeter values, history suggestive of sleep apnoea) , for renal lesions and for splenic enlargement (impalpable) by ultras ound or computerized tomography. 7 patients had erythroid culture scor es suggesting primary polycythaemia but the addition of non-culture cr iteria did not result in any scores more strongly predictive of primar y polycythaemia. Supine oximeter values <92% suggested hypoxaemia as t he mechanism of polycythaemia in 3 patients in whom it had not previou sly been suspected. Some splenic enlargement (impalpable) was demonstr ated in 6 patients, only 1 of whom had erythroid culture scores sugges ting primary polycythaemia. 12 patients had confirmed, raised erythrop oietin levels. We conclude that idiopathic erythrocytosis refers to a heterogenous group of patients. Features of primary or secondary polyc ythaemia may be demonstrated in some of them by additional new study t echniques. The raised erythropoietin values found in half the patients were unexpected.