Increased Levels of ICOS and ICOSL Are Associated to Pulmonary Arterial Hypertension in Patients Affected by Connective Tissue Diseases

Background: Pulmonary hypertension (PH) is a life-threatening complication of connective tissue diseases (CTD); in this study, we aimed at investigating the potential role of inducible co-stimulator (ICOS) and its ligand (ICOS-L) as biomarkers of PH in CTD. Materials and Methods: We recruited 109 patients: 84 CTD patients, 13 patients with CTD complicated by pulmonary arterial hypertension (PAH), and 12 subjects with PAH alone. All recruited patients underwent a complete clinical and instrumental assessment along with quantitative measurement of serum ICOS and ICOS-L. Results: Independently of the underlying cause, patients with PAH were older and had a lower glomerular filtration rate. Interestingly, patients with both CTD-related and CTD-unrelated PAH had higher ICOS and ICOS-L serum concentrations than CTD patients (0.0001 for both). When compared to CTD patients, those affected by CTD-PAH showed higher ICOS (440 (240-600) vs. 170 (105-275) pg/mL, p = 0.0001) and ICOS-L serum concentrations (6000 (4300-7000) vs. 2450 (1500-4100) pg/mL; p = 0.0001). In a logistic regression, ICOS and ICOS-L were associated with a diagnosis of PAH, independently from age, gender, and renal function. The corresponding receiver operating characteristic (ROC) curves demonstrated a good diagnostic performance for both ICOS and ICOS-L. Conclusions: ICOS and ICOS-L are increased in patients with PAH, irrespectively from the underlying cause, and represent promising candidate biomarkers for the diagnostic screening for PAH among CTDs patients.

Automated summary

This study found that the concentrations of ICOS and ICOS-L in the serum of patients with pulmonary arterial hypertension (PAH) were higher, regardless of the underlying cause. When compared to CTD patients, CTD-PAH patients had higher concentrations of ICOS and ICOS-L. Logistic regression analysis showed that ICOS and ICOS-L were associated with a diagnosis of PAH. ICOS and ICOS-L may serve as promising candidate biomarkers for the diagnostic screening of PAH among CTD patients.