A comparison of three brands of polysulfone membranes

A prospective clinical crossover study comparing the functional performance and biocompatibility of three brands of polysulfone membranes (Fresenius Polysultone (Fresenius Ag, Bad Homburg, Germany), Polyphen (Minntech Corp., Minneapolis, MN), and Biosulfane (WR Grace Inc., Danvers, MA)) incorporated in ethylene oxide-sterilized dialyzers of comparable surface area (1.3 to 1.35 m2) was undertaken. The clearance of small molecules by each membrane was comparable. Plasma levels of beta 2 microglobulin fell to 49.9% of pretreatment values by 210 min when using the Fresenius Polysulfone membrane, 60.2% with the Polyphen membrane, and 63.1% with the Biosulfane membrane. The reduction achieved by the Fresenius Polysulfone membrane was superior (P = 0.003). The plasma reductions were associated with the recovery of 195 mg beta 2 microglobulin from the dialysate for the Fresenius Polysulfone membrane and 158 mg for the Polyphen membrane, but no beta 2 microglobulin was recovered from the dialysate with the Biosulfane membrane. The dialysate collected with the Fresenius Polysulfone membrane also contained a mean of 6853 mg of total protein, compared with 5490 mg with the Polyphen membrane and 8422 mg with the Biosulfane (P = 0.04) membrane. The neutropenia was slight and independent of membrane brand, as were the changes in C3a des arg and SC5b-9 complement components. The reduction in platelet counts was higher for the Biosulfane membrane than for the other brands (P = 0.003). This study indicates that whereas the polymer base of the membrane is the same, its production and subsequent handling during dialyzer production induce changes that attain statistical significance, most notably in the way that the membrane removes beta 2 microglobulin and interacts with proteins. The differences observed are a consequence of the different alloying polymers used during manufacture and, consequently, the membranes cannot be considered equivalent.