Clinical trials of a cryoglobulin filter.

The authors report the results of clinical trials of a high capacity cryoglobulin filter (Cryofilter) in seven patients with cryoglobulinemia unresponsive to high doses of prednisone or immunosuppressive drugs who required plasmapheresis. The objective of this study was to test the safety and efficacy of the cryofilter in a limited patient population according to the investigational Device Exemption guidelines of the FDA. The cryoglobulins were selectively filtered from plasma at 4 degrees C by a cryofilter characterized by a membrane surface area of 0.135 m2 and an average pore size of 4.3 microns. Safety was evaluated by patients vital signs, complement activation, and clinical score of symptoms in the course of 10 treatments. Efficacy of cryofiltration was evaluated by comparing sieving of the cryoglobulins to that of albumin; immunoglobulins G, A, and M; and fibrinogen. All seven patients completed the series of 10 treatments without notable complement activation or any signs of discomfort. The cryofilter was particularly selective in patients with high cryoglobulin concentrations. Improvement in clinical symptoms was observed in all patients.