Oxygenated hemoglobin as prognostic marker among patients with systemic sclerosis screened for pulmonary hypertension

Abstract

<b>Background:</b> Oxygenated hemoglobin (OxyHem) in arterial blood may reflect disease severity in patients with systemic sclerosis (SSc), particularly among those with pulmonary manifestations such as pulmonary hypertension (PH). Hence, the aim of this study was to analyze the predictive value of OxyHem in SSc patients screened for PH. <b>Methods:</b> SSc patients were screened for PH including right heart catheterisation, laboratory and clinical assessment. They were followed for 3.2±2.6 (median 3.0) years. OxyHem was measured by multiplying the concentration of hemoglobin with oxygen saturation assessed in arterialized capillary blood. Kaplan-Meier analysis was performed using the defined threshold from Receiver Operating characteristic. Prognostic power was compared with known parameters of prognostic significance in SSc using uni- and multivariable analysis. Clinical parameters of patients with high and low OxyHem were compared by student’s t-test. <b>Results:</b> 280 SSc patients were screened, 267 were included in the analysis (82% female, 59.8±13.4 years, 73.8% limited cutaneous SSc), 56 patients had manifest PH and 112 pulmonary fibrosis. Low OxyHem ≤12.5 g/dl at baseline was significantly associated with a worse survival (p=0.046) among SSc patients. In the multivariable analysis the presence of ILD, age ≥60 years and diffusion capacity (DLCO) ≤65% were associated with worse survival among SSc patients. The combination of low DLCO and low OxyHem at baseline could predict the development of early pulmonary vascular disease at follow-up (sensitivity 79.6%). <b>Conclusions:</b> This study detected for the first time that an OxyHem level ≤12.5 g/dl is a prognostic predictor in SSc patients.