Pulmonary function study of myasthenia-gravis patients treated with double-filtration plasmapheresis

The aim of this study was to investigate the changes in pulmonary function tests for patients with myasthenia gravis (MG) after treatment with double filtration plasmapheresis (DFP) and to evaluate whether pulmonary function tests predict the efficacy of DFP treatment. Thirty-five MG patients (20 females and 15 males, age range 21-69 years) underwent DFP for between four and eight consecutive sessions. Vital capacity (VC), maximal inspiratory pressure (Pi(max)), and MG score were measured before and after DFP. Based on the results of pulmonary function tests, the patients were divided into dyspnea (VC < 1.0 L or Pi(max) < -25 cm H(2)O) and control groups (VC > 1.0 L and Pi(max) > -25 cm H(2)O). The dyspnea group had a significantly better response to DFP treatment, reflected in the decrease of the MG-score (P=0.0327), and the increase in VC value (P=0.0561). Higher clearance rates of acetylcholine receptor antibody (AchRAb) had a trend toward higher changes of VC. In conclusion, VC might better serve as a predictor for the effect of DFP in the dyspnea patient group because of better correlation with clinical improvement and AchRAb clearance.