HRCT in systemic sclerosis: correlation between respiratory functional indexes and extension of lung failure

The purpose of the study was to identify the correlation between functional lung parameters to the extent of lung involvement evaluated by High Resolution Computed Tomography (HRCT) in systemic sclerosis (SSc), using a modified score scale. Forty-two patients with established clinical diagnosis of systemic sclerosis were retrospectively selected from the hospital information system and were prospectively included in the study protocol undergoing chest radiography, HRCT and functional lung testing. Lung involvement was assessed by HRCT, lesions were assessed in the individual segments and an additional severity score was introduced by assigning 3 points for bilateral lesions. The total new HRCT score was statistically related to severity of functional lung parameters. Thirty-six out of 42 patients showed an interstitial lung involvement by HRCT: Ground Glass (GG) n=36/42 of which n=27/36 were bilateral; IPM n=30/42, of which 24/30 were bilateral; SL n=33/42 of which 18/33 were bilateral; HC n=6/42 of which 6/6 were bilateral; SC n=6/42 of which 3/6 were bilateral.18/42 had a total score between 0-10, 6/42 between 11-20, 12/42 between 21-30, 6/42 greater than 31. Fifteen out of 42 had restrictive deficit. The results of functional respiratory testing were: FVC less than 80 percent in 12/42 patients (28.5 percent), TLC less than 80 percent in 15/42 patients (35.7 percent), DLCO less than 80 percent in 38/42 patients (90.4 percent) and DLCO/VA less than 80 percent in 21/42 patients (50 percent). The total score was statically related with FVC and TLC and with DLCO and DLCO/VA showing a significant negative correlation found between the total HRCT score of extent of lung damage and lung-function parameter (TLC: r= -0.65, P=0.00000264; FVC: r= -0.50; P=0.000575; DLCO: r= -0.74, P=2.02E-8; DLCO/VA: r= -0.68, P=0.0000005). All Pairwise Multiple Comparison Procedures showed a significant difference between the two rank sums that enclosed the comparison for DLCO/VA vs SCORE and DLCO vs SCORE. In conclusion, our modified score scale gives interesting additional data to evaluate the extension of interstitial lung involvement in SSc. It is inversely proportional to spirometry and DLCO and DLCO/VA. The bilateralism of the lesions is directly proportional to the lung damage.