[Development of polycythemia to myelofibrosis. Monitoring by the assay of the procollagen III amino-propeptide].

The conventional methods used in the follow-up of myelofibrosis being both invasive and expensive, we propose an easy and sensitive immunoassay of the procollagen III aminoterminal peptide (propeptide) which is separated and released in serum during synthesis of collagen III by bone marrow fibroblasts. This propeptide was assayed in the sera of 25 healthy adults (controls), 48 patients with polycythaemia vera and 20 patients with myelofibrosis (secondary to polycythaemia in 14). Significant differences in mean values were found between controls (7.6 +/- 2.1 ng/ml), patients with polycythaemia (9.9 +/- 4.3 ng/ml) and patients with myelofibrosis (38.1 ng/ml). There was some overlapping between values in controls and in patients with polycythaemia, partly due to the fact that 12 of these 48 patients without reticulin bone marrow fibrosis had normal serum propeptide levels. Propeptide values in patients with myelofibrosis were much scattered (range: 13-103 ng/ml). Moreover, values above 25 ng/ml were associated with myelofibrosis of recent onset (less than or equal to 2 years) and values below 25 ng/ml with myelofibrosis of more than 4 years' duration. The procollagen III aminoterminal peptide immunoassay therefore is a non-invasive and sensitive method for accurate assessment of bone marrow progressive involvement in myeloproliferative diseases associated with myelofibrosis. It could also be used to evaluate the effectiveness of antifibrosing agents.