AA genotype of IL-8 -251A/T is associated with low PaO(2)/FiO(2) in critically ill patients and with increased IL-8 expression

Interleukin-8 (IL-8) is a central chemokine in acute respiratory distress syndrome (ARDS), and the IL-8 gene contains a functional single nucleotide polymorphism (SNP) -251A/T in its promoter region. We hypothesized that IL-8 -251A/T SNP is associated with PaO(2)/FiO(2) in critically ill patients. We conducted genetic-association studies in intensive care units at academic teaching centres using a derivation septic shock cohort (vasopressin and septic shock trial (VASST), n = 467) and a validation post-cardiopulmonary bypass surgery cohort (CPB, n = 739) of Caucasian patients. Patients in both cohorts were genotyped for IL-8 -251A/T. The primary outcome variable in both cohorts was the fraction of patients who had a PaO(2) /FiO(2) < 200. IL-8 mRNA expression was measured in genotyped lymphoblastoid cells in vitro. The frequency of the patients with PaO(2)/FiO(2)