Risk factors for thromboembolic events in patients with paroxysmal nocturnal hemoglobinuria (PNH): a nested case–control study in the International PNH Registry

The objective of this analysis was to identify risk factors for thromboembolic events (TE) in patients with paroxysmal nocturnal hemoglobinuria (PNH) who were not treated with C5 inhibitors. Patients with PNH and a history of ≥ 1 TE at enrollment in the International PNH Registry (NCT01374360; registration date, January 2011) were each matched with up to 5 patients without TE. Multivariable analysis was performed with the following variables: percentage glycosylphosphatidylinositol (GPI)–negative cells, high disease activity (HDA), non-TE major adverse vascular event history, and recent anticoagulation. Of 2541 eligible patients, 57 with TE and 189 matched controls were analyzed. Multivariable analysis (odds ratio [95% CI]) identified the following factors as being associated with increased thrombotic risk: patients with no history of TE (with recent anticoagulation, 9.30 [1.20–72.27]), patients with history of TE (with recent anticoagulation, 8.91 [0.86–92.62]; without recent anticoagulation, 5.33 [0.26–109.57]), patients with ≥ 30% GPI-negative granulocytes (≥ 30% to < 50%, 4.94 [0.54–45.32]; ≥ 50%, 1.97 [0.45–8.55]), or patients with lactate dehydrogenase (LDH) ratio ≥ 1.5 × upper limit of normal (ULN) plus ≥ 2 HDA criteria (2–3 criteria, 3.18 [0.44–23.20]; ≥ 4 criteria, 3.60 [0.38–33.95]). History of TE, ≥ 30% GPI-negative granulocytes, and LDH ratio ≥ 1.5 × ULN with ≥ 2 HDA criteria are TE risk factors for patients with PNH. These findings will aid physicians by providing important clinical and laboratory risk factors that can be used to identify and manage patients with PNH who are at risk of developing TE.