Effect of angiotensin converting enzyme gene I/D polymorphism and its expression on clinical outcome in acute respiratory distress syndrome

Background. The role of the D allele of the angiotensin-converting enzyme (ACE) gene I/D polymorphism in the clinical outcomes of patients with acute lung injury and acute respiratory distress syndrome (ALI/ARDS) remains controversial. Our aim was to assess simultaneously the effect of the ACE I/D polymorphisms as well as the serum and BALF ACE levels on prognosis of patients with ARDS. Methods. Sixty-nine mechanically ventilated patients with ALI/ARDS were recruited. ACE activity levels both in serum and BALF were assessed by chemical methods. Patients were genotyped for ACE I/D polymorphisms. Time-to-event analysis evaluated the variables associated with the 28-day and 90-day mortality. Finally, we performed a meta-analysis of studies examining the association between ACE I/D polymorphisms and mortality of ALI/ARDS patients. Results. In the multivariable model, age, lung compliance, serum lactate and serum ACE levels were significantly associated with both 28-day and 90-day mortality. No significant correlation was found between serum and BALF ACE levels (Spearman's rho=0.054; P=0.66). Serum ACE concentrations were significantly higher (P=0.046) in patients with D/D genotype versus the two other groups combined (I/D and I/I genotypes). The meta-analysis of 6 studies (including ours) provided evidence that D allele is significantly associated with increased mortality in ALI/ARDS patients, yielding a per-allele odds ratio of 1.76 (95% CI: 1.19, 2.59). Conclusion. Serum ACE levels appear to be affected by the I/D polymorphism and are correlated with prognosis in patients with ALI/ARDS indicating that further investigation of the clinical significance of the ACE in ARDS might be of value