Plasma interleukin-6 adds prognostic information in pulmonary arterial hypertension

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 (RD 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 …