Paroxysmal nocturnal hemoglobinuria: Test to monitor the action of eculizumab treatment.

INTRODUCTION: Paroxysmal nocturnal hemoglobinuria (PNH) is caused by a somatic mutation in the PIG-A gene, which encodes for glycosylphosphatidylinositol, a phospholipid membrane that anchors proteins like CD55 and CD59. These proteins are inhibitors of the complement-mediated lysis. PNH is diagnosed by flow cytometry, and treatment with eculizumab improves the life quality of patients with severe clinical compromise. The aim of this work was to evaluate a hemolytic test that allows monitoring the blockade of the alternative complement pathway caused by eculizumab (herein MET test). METHODS: There were analyzed a total of 163 serum samples from nine patients with PNH under treatment with eculizumab and ten healthy volunteers like controls. The patients were evaluated for 6 months. The MET test consisted in incubating red blood cells from patients (RBCPNH ) with either acidified serum from healthy volunteers and from patients with PNH. The results can be (a) Positive, (b) Blockade profile, or (c) Negative. RESULTS: Seven patients responded favorably to the eculizumab, and the test evidenced the blockade profile. The two remaining patients were nonresponders to the treatment, with a positive MET test. In these patients, the dose was increased. One responded favorably with a blockade profile, and the other continued to be nonresponder. CONCLUSIONS: The MET test proved to be a useful tool to monitor the blockade of complement by eculizumab.