OBJECTIVETo study the effects of low-molecular weight heparin (LMWH) and adrenocortical hormone (dexamethasone) on the hemolysis of red cells of patients with paroxysmal nocturnal hemoglobinuria (PNH) in vitro.

METHODSUsing Ham's test and micro-complement lysis sensitive test (mCLST), the changes in hemolysis of red cells from 6 typical PNH cases were examined after adding LMWH and dexamethasone in different concentrations into the test solution in vitro. The effects of LMWH and dexamethasone on the coagulation of the tested blood samples were also studied using the activated partial thromboplastin time (APTT) test.

RESULTSBoth LMWH and dexamethasone inhibited the hemolysis of PNH red cells, and they also showed a synergistic effect. The inhibiting effects were dose-dependent. Moreover, a tolerable dose of LMWH induced a limited prolongation of APTT. Dexamethasone showed two possible mechanisms in the inhibition of PNH red cells hemolysis through Ham's test and mCLST, respectively: (1) inhibiting both antibodies binding to red cells and (2) the initiation of the activation of complement 3 (C3). LMWH could inhibit hemolysis as determined by both Ham's test and mCLST, which indicated that LMWH could block the activation of complement cascade.

CONCLUSIONSBoth LMWH and dexamethasone could inhibit hemolysis in PNH, and they showed a synergistic effect. Their mechanisms of inhibiting hemolysis differed from each other. Furthermore, a tolerable dose of LMWH induced a limited prolongation of APTT. LMWH might be useful for controlling acute hemolysis in patients with PNH and reducing the dose of adrenocortical hormone.