MPO and acute respiratory distress syndrome: Overall, ARDS/ALI patients showed higher levels of albumin (SMD: 2.15; P = 0.010), ANG‐1 (SMD: 4.60; P < 0.001), KL‐6 (SMD: 2.23; P = 0.044), myeloperoxidase (MPO) (SMD: 1.75; P < 0.001), transforming growth factor (TGF)-β1 (SMD: 0.83; P = 0.013), transfer factor (TF) (SMD: 5.57; P < 0.001), and TNF receptor‐1 (SMD: 5.40; P < 0.001).