Clinical Characteristics of Connective Tissue Disease-Associated Interstitial Lung Disease in 1,044 Chinese Patients

Background Because the prevalence of connective tissue disease (CTD)-associated interstitial lung disease (ILD; CTD-ILD) in China is unknown, we wanted to analyze the clinical characteristics of this disease in Chinese patients. Methods The medical records of patients who received a diagnosis of ILD and treated in Shanghai Pulmonary Hospital from January 1999 to January 2013 were reviewed. Based on the records, patients who also received a diagnosis of CTD were identified, and their records of follow-up examinations for a minimum of 12 months until the end of December 2013 were reviewed. Results Of the 2,678 patients who received a diagnosis of ILD, 1,798 (67%) were identified as having CTD-ILD; 299 (11.2%) had idiopathic pulmonary fibrosis (IPF). Complete clinical data were available for 1,044 patients with CTD-ILD and 178 with IPF. We found that 332 of the 1,044 patients with CTD-ILD (32%) did not receive an accurate diagnosis at the initial hospital admission, 195 (18.7%) of the 1,044 patients showed persistent negative test results for autoantibodies, and 262 (25.1%) of the 1,044 patients had negative autoantibodies at the initial hospital admission and then became positive at follow-up examinations. Of the 288 patients who had confirmed CTD-ILD, 41 (14%) showed pulmonary symptoms as the initial clinical manifestation (PSIM) and 247 (86%) showed extrapulmonary symptoms as the initial clinical manifestation (EPSIM). For the 756 patients who had undifferentiated CTD-ILD, the proportion of PSIM and EPSIM was 44% and 56%, respectively. For patients who presented with PSIM, 23 who had confirmed CTD-ILD (56%) and 216 who had unconfirmed CTD-ILD (65%) did not receive an accurate diagnosis at the initial visit but were ultimately diagnosed at subsequent follow-up examinations. Conclusions Patients with CTD-ILD do not receive an accurate diagnosis at the initial hospital admission possibly because of negative serologic test results for autoantibodies and the absence of obvious extrapulmonary symptoms. Thus, patients with ILD should be examined for extrapulmonary symptoms and tested for autoantibodies at follow-up examinations.