**3. Results**

Descriptive data of patients included in Ssc group and healthy controls are presented in Table 1.


**Table 1.** Characteristics of included Ssc patients and healthy controls.

NS—not significant, PAP—pulmonary artery pressure, DLCO—diffuse lung capacity for carbon monoxide, ANA—antinuclear antibody, ESR—erythrocyte sedimentation rate; CRP—C-reactive protein; ACE—angiotensin-converting enzyme. n◦— number; N/A—not applicable.

#### *3.1. Serum Calumenin in Ssc Patients*

**Serum Calumenin (ng/mL)**

Serum calumenin levels were higher in Ssc patients compared to controls (median 26.14 ng/mL (interquartile range—IQR 27.22) versus median 17.97 ng/mL (13.82), Mann Whitney U test, *p* = 0.002, Figure 1). Ssc patients with a modified Rodnan score ≥ 14 (thus with diffuse cutaneous fibrosis) had higher circulatory calumenin levels. Median calumenin levels in Ssc patients with diffuse cutaneous fibrosis were 30.55 ng/mL (30.12) versus 20.08 ng/mL (16.57), Mann Whitney U test, *p* = 0.015

≥

≥

**Figure 1.** Serum calumenin levels were higher in Ssc (systemic sclerosis) patients compared to healthy controls (*p* = 0.002, Mann Whitney U test). The circles, stars and numbers in figure represent the patient ID in the database that are considered outliers by the statistical software used.

When used as a diagnostic test for diffuse cutaneous fibrosis, calumenin had a relatively good diagnostic capacity AUROC = 0.70 (95% confidence interval (0.56–0.86)), Figure 2.

**Figure 2.** ROC curve for calumenin as diagnostic test for diffuse cutaneous fibrosis. AUROC = 0.70, 95% confidence interval 0.56–0.86.

In addition, patients with daily or higher frequency of Raynaud phenomenon had higher calumenin levels (30.36 ng/mL (35.11) versus 17.84 ng/mL (12.24), Mann Whitney U test, *p* = 0.006).

Patients with low C3 or C4 levels also had significantly higher calumenin levels (median 54.34 ng/mL (116.04) versus 23.71 ng/mL (15.19), Mann Whitney U test, *p* = 0.03). Circulating calumenin levels were positively correlated with modified Rodnan scores (r = 0.40, *p* = 0.004) with CRP levels (r = 0.343, *p* = 0.02) and with ESR (r = 0.372, *p* = 0.01).

Interestingly, patients with pulmonary fibrosis had a tendency for higher circulatory calumenin levels (30.22 ng/mL (34.62) versus 21.5 ng/mL (12.70) *p* = 0.087, Mann Whitney U test). Nevertheless, no significant differences between serum calumenin levels in diffuse versus localized Ssc patients were found.
