RESULTS
Patients were divided into two groups; SSc patients with any typical morphological findings of PF on HRCT (n=41) and patients without any typical morphological findings of PF on HRCT (n=94). These were compared with healthy controls (n=38). These three groups were comparable in age and gender distribution (49.8±15.4, 50.2±11.5, 52.2±5.80,p =0.563; female 85.4%, 88.3%, 89.5%, p =0.840, respectively). Baseline demographic and clinical characteristics and laboratory results of the SSc patients with and without PF are shown in Table 1. The patients with PF had more diffuse cutaneous involvement, lower FVC and DLCO, and were more likely to be Scl-70 autoantibody positive. Pulmonary artery diameter was higher in the patients with PF, and more patients had pulmonary artery dilatation when a cut-off value of 30 mm was used (p <0.001 and p =0.002, respectively). Synovitis was more common in patients without PF.
The soft-ware analysis was performed on HRCT images of the 135 patients with SSc and 38 controls (Figure 2). Analysis of the right and left lung density, right and left lung volume derived from the baseline HRCT scanning in SSc patients with PF, SSc patients without PF, and control group was performed (Table 2, Figure 2). Comparison of the lung measurements showed the right and left lung densities were significantly increased, and the right and left lung volumes were significantly decreased in SSc patients with PF than SSc without PF and controls. The pairwise comparisons between the groups revealed there were no differences between the SSc patients without PF and controls in terms of right and left lung densities (p =1.000 and p =1.000, respectively); there was a significant difference between SSc patients with and without PF in terms of right and left lung volumes (p =0.005 and p =0.003, respectively).
Patients without evidence of PF were sub-grouped into limited (n=71) and diffuse (n=23) cutaneous involvement. This showed that the right and left lung densities (p =0.002 and p <0.001, respectively), and the right and left lung volumes differed significantly between the groups (p =0.045 and p =0.044, respectively) (Table 3).
Sixteen out of 56 (28.6%) patients without any signs of PF at initial evaluation and who had an annual follow-up CT scans developed abnormal imaging after a mean duration of 10±5 years. Baseline lung densities and volumes were compared between these sub-groups. This revealed that the baseline right and left lung densities were significantly lower in the patients who developed signs of PF during follow-up than those who did not (p =0.016 and p =0.014, respectively) (Table-4).
The correlation between FVC and DLCO and lung densities and volumes in patients with and without PF was analyzed separately. Spearman rank correlation demonstrated negative correlation between the FVC and left lung density (r =-0.230, p =0.043) and positive correlation between FVC and right and left lung volumes (r =0.331,p =0.003; r =0.299, p =0.008, respectively) in the patients without PF signs while DLCO correlated only with left lung volume in these patients (r = 0.248, p =0.032). In the patients with PF, FVC correlated negatively with right and left lung densities (r = -0.601, p =0.001; r = -0.507,p =0.005, respectively) and positively with left lung volume (r = 0.500, p =0.006). Similarly, DLCO correlated negatively with right and left lung densities (r =-0.487, p =0.012;r = -0.393, p =0.047, respectively) and positively with left lung volume in these patients (r = 0.402, p =0.042) (Table 5).