To the Editor:
Noninvasive biomarkers are needed to aid in making challenging clinical decisions in pulmonary arterial hypertension (PAH). Several biomarkers have been described, but only the natriuretic peptides have gained clinical utility. A key question to answer is whether or not a new biomarker adds independent incremental information [1]. Novel PAH markers may be discovered from new pathobiological pathways, such as inflammation. In particular, interleukin (IL)-6 has been linked with the development of severe pulmonary hypertension in animal models, mimicking the pathology of human disease [2]. IL-6 is a major regulator of the production of C-reactive protein (CRP), a marker of cardiovascular risk [3]. We conducted this study to determine if these inflammatory biomarkers add incremental prognostic information in PAH.
This is a cohort study based on a prospective Biobank. We enrolled patients with idiopathic, heritable, connective tissue-associated and congenital heart disease-associated PAH, as defined by current guidelines [4], between March 2005 and June 2011. The study was approved by the Cleveland Clinic Institutional Review Board. We used ELISA (R&D Systems Inc., Minneapolis, MN, USA) to measure IL-6, the Abbott platform for highly-sensitive CRP (hsCRP) (Abbott Laboratories, Abbott Park, IL, USA) and a chemiluminescence immunoassay to measure B-type natriuretic peptide (BNP) (ADVIA Centaur XP; Siemens Healthcare Diagnostics, Inc., Tarrytown, NY, USA) Peripheral plasma samples were kept at -80°C until retrieved for the measurement of the biomarkers (September 2011 for hsCRP and BNP, and February 2012 for IL-6). Investigators who performed the biomarker determination were blinded to the study participants’ outcomes.
All-cause mortality since the date of study blood sampling was ascertained via manual and automated …