Clinical significance of serum pro-collagen III in chronic myeloproliferative disorders.

Pro-collagen III (PC III) has been proposed as a useful value for diagnosis and follow-up of myeloproliferative disorders. A significant difference is observed between polycythaemia vera (PV) and essential thrombocythaemias (ET) on one hand, and the pure erythrocytoses (PE) on the other hand, but a large overlap makes this test of low diagnostic value. High values are observed in primary and post-PV myelofibrosis, but excessive PC III levels in active PV are not predictive of evolution toward myelofibrosis. PC III level is lower in myelo-suppressed patients (32P, or hydroxy-urea) than in active cases or in patients treated by phlebotomies. We conclude that PC III measurement is of low diagnostic value for discriminating PV and PE, does not appear to allow short-term prediction of evolution to myelofibrosis, but may be useful to evaluate the role of treatment in delaying progression of PV toward myelofibrosis.