HIGH THROUGHPUT MULTIPLEX ASSAY IDENTIFIES CLINICALLY MEANINGFUL CLUSTERS IN SYSTEMIC SCLEROSIS PATIENTS WITH LOW CARDIOVASCULAR RISK AND NO HISTORY OF HEART DISEASE.

Abstract

Introduction: People with systemic sclerosis (SSc) often show subclinical evidence of primary heart involvement (pHI), which when clinically evident, is a prognostic factor of poor outcome. We aimed to profile serum proteins in patients with SSc and no history of pHI and identify clinically meaningful clusters to aid early identification and stratification for pHI. Material(s) and Method(s): Serum from 78 patients from CONVAS ('CONnective Tissue Disease and VASculitis Cohort') and ELCASA ('ELectrophysiology and CArdiac imaging in SclerodermA') cohorts with no history of pHI, pulmonary hypertension, diabetes or more than 2 traditional cardiovascular (CV) risk factors was used to measure levels of 355 proteins across inflammation, cardiometabolic and cardiovascular II/III Olink panels. Unsupervised hierarchical clustering using scaled normalised protein expression (NPX) was used to define clusters. Demographic and clinical characteristics were compared between clusters and significant differences reported using Kruskal Wallis rank sum test for continuous or Pearson's chi-squared test for categorical variables, at the 5% significance threshold. Result(s): Clinical characteristics of the patient cohorts have been previously published and are summarised in fig 1A (column 2). Unsupervised hierarchical clustering revealed 3 patient clusters-C1 [27/78 (35%)], C2 [33/78 (42%)] and C3 [18/78 (23%)] with intermediate, low and high protein expression respectively (fig 1B). C2 patients were younger (median age 51 years) compared to C1 (61 years) and C3 (58 years) (p <0.001). High expression cluster C3 had a significantly higher proportion of males [7/18 (39%)](p = 0.009), shorter disease duration [median 1.15 years, IQR (0.66 to 7.23)], higher modified Rodnan skin scores (MRSS) [median 5.50, IQR (3.25 to 11)] (p = 0.002) and current disease modifying anti-rheumatic drugs (DMARD) use [16/18 (89%)](p = 0.005). NTproBNP and CRP were elevated in C1 and C3, and high-sensitivity troponin I (hsTnI) was highest in C3[median 6.15 IQR (5.08 to 89.58)](p = 0.002); n=3 within C1 (black box fig 1A) showed especially high NTproBNP (median 227.50pg/ml) and CRP (median 13mg/dl). No differences in antibody profiles were noted across the three clusters (fig 1A). Conclusion(s): Differences in serum protein expression identifies clinically meaningful clusters of SSc patients with elevated acute phase and serum cardiac markers despite low CV risk profile. Future work should assess their utility as prognostic biomarkers of SSc-pHI.