MR-pro-atrial natriuretic peptide (MR-proANP) predicts short- and long-term outcomes in respiratory tract infections: a prospective validation study

BACKGROUND: Previous research found precursor levels of the atrial natriuretic peptide (MR-proANP) to be promising prognostic markers. This study aims to validate these findings and describe patterns of MR-proANP in a large cohort of patients with lower respiratory tract infections. METHODS: We conducted a multicenter prospective cohort study, and measured MR-proANP in patients with lower respiratory tract infections on admission, and days 3, 5 and 7. The prognostic value of MR-proANP for predicting 30-day and 180-day mortalities was evaluated. We stratified MR-proANP levels a priori into quartiles, and compared it with severity of illness using the pneumonia severity index. RESULTS: A total of 1359 patients, including 925 with community-acquired pneumonia, were enrolled. The mortality risk at days 30 and 180 significantly increased with increasing MR-proANP quartiles ( 158-311 pmol/L, and <311 pmol/L). This was true for low-risk, as well as high-risk subjects (pneumonia severity index classes I-III and IV-V). In Kaplan-Meier survival curves, MR-proANP quartiles significantly separated survivors from non-survivors in the overall cohort (p log-rank>0.001), and in low-risk (p log-rank>0.03) and high-risk (p log-rank=0.007) pneumonia severity index patients at day 30. In multivariate logistic regression analysis, MR-proANP was an independent risk factor for 30-day and 180-day mortalities (odds ratio per unit increase of log transformation MR-proANP level: 5.58, 95%CI 1.97-15.82 and 5.08, 95%CI 2.44-10.60). CONCLUSION: This study confirms the high prognostic performance of MR-proANP for short- and long-term mortality, particularly its high negative predictive value, in lower respiratory tract infections and community-acquired pneumonia, thereby complementing clinical risk assessment with the pneumonia severity index.