A COMPARISON OF FVC, FVC/DLCO AND TLC/DLCO AS AN INDICATOR FOR INTERSTITIAL LUNG DISEASE IN PATIENTS WITH SCLERODERMA

Abstract

SESSION TITLE: Characteristics of Interstitial Lung Disease SESSION TYPE: Original Investigations PRESENTED ON: 10/10/2018 02:30 pm - 03:30 pm PURPOSE: Pulmonary function tests (PFTs) have been reported to be unreliable for the identification of interstitial lung disease (ILD) in Scleroderma patients. A normal Forced Vital Capacity [FVC], was reported in 62.5% of these Scleroderma patients with significant ILD on high resolution CT (HRCT) of chest. The correlation of FVC/DLC and TLC/DLCO to pulmonary fibrosis in Scleroderma patients has not been studied. The objective of this study was to compare the correlation between FVC, Total Lung capacity [TLC] / Diffusion Capacity [DLCO]) ratio and FVC/DLCO ratio, respectively, with the extent of ILD measured by a fibrosis score on HRCT of chest in patients with Scleroderma. METHODS: The records of 40 patients with Scleroderma without Pulmonary Arterial Hypertension followed at the rheumatology clinic our institution were reviewed. Patient demographics and PFT parameters (FVC, TLC, and DLCO) were noted. FVC/DLCO and TLC/DLCO was calculated for each patient. Patients’ chest HRCT scans were graded by a radiologist for ILD by a HRCT Fibrosis Score, calculated by estimating the percentage of parenchymal involvement in three zones (upper, middle, lower) of each lung, with a score of 100 representing normal and a score of 400 representing severe fibrosis. PFT variables were recorded as percent predicted (%) and expressed as mean + SD. Pearson’s test for linear correlation was used to determine correlation of Fibrosis Score with respectively-FVC, FVC/DLCO and TLC/ DLCO. RESULTS: Mean age was 58.8 +/- 12.9 years; 76% were females; 74% had limited disease. Mean FVC: 87.80 +/- 23.52 %; mean TLC: 94 +/-15.9 %; mean DLCO :72.8 +/- 21%; mean FVC/DLC: 0.20 +/- 0.5; mean TLC/DLCO: 0.33 +/- 0.08. Normal FVC was seen in 70%; normal TLC in 85%.; normal DLCO in 32.5%. Mean fibrosis score was:105.2 +/- 11.3 (Range: 100-280). Using Pearson’s correlation analysis, correlation between fibrosis-score and respectively FVC, FVC/DLC and TLC/DLCO was as follows: FVC vs. Fibrosis Score: r= -0.313; p=0.04; FVC/DLCO vs. Fibrosis Score: r= -0.119; p=0.46; TLC/DLCO vs. Fibrosis Score: r=0.06; p =0.69. CONCLUSIONS: ILD in Scleroderma, estimated by the Fibrosis score, correlates significantly with FVC but not with FVC/DLCO and TLC/ DLCO. CLINICAL IMPLICATIONS: Despite prior studies reporting FVC as an unreliable indicator of ILD in Scleroderma, our study shows that FVC has a strong correlation with pulmonary fibrosis in Scleroderma. Further studies are needed to re-evaluate this. DISCLOSURES: No relevant relationships by Debapriya Datta, source=Web Response No relevant relationships by Carol Halasan, source=Web Response No relevant relationships by Sophie Korzan, source=Web Response