The interstitial lung disease spectrum under a uniform diagnostic algorithm: a retrospective study of 1,945 individuals

BACKGROUND: Reported data on the disease spectrum of interstitial lung diseases (ILDs) of China are sparse and varied. We aimed to investigate the spectrum of ILDs and the distribution of diagnostic methods under a uniform diagnosis. METHODS: This retrospective study enrolled ILDs cases from Guangzhou Institute of Respiratory Health (GIRH). All cases were classified into specific subgroups of ILDs according to updated guidelines. RESULTS: A total of 1,945 subjects were enrolled from January 2012 to December 2017. The mean age was 57.9 years, and 1,080 (55.5%) patients were male. The most common subtype of ILDs was idiopathic pulmonary fibrosis (IPF, 20.3%), followed by interstitial pneumonia with autoimmune features (IPAF, 17.9%), connective tissue disease associated ILD (CTD-ILD, 18.3%) and unclassifiable idiopathic interstitial pneumonia (UIIP, 14.7%). A total of 818 (42.1%) patients underwent lung biopsy in order to obtain a histological diagnose. TBLB was performed in 565 (29.0%) patients, eleven of whom underwent SLB because TBLB failed to obtain lung samples. SLB was performed in 213 (11.0%) patients and TBCB was performed in 51 (2.6%) patients. Among them, histological results were considered clinically helpful in 722 (88.3%) cases, and provided definitive histopathological diagnoses in 368 cases. Surgical lung biopsy (SLB) was performed in 213 (10.9%) subjects, while 115 (54.0%) cases were performed among the idiopathic interstitial pneumonia (IIP). Among SLB cases in IIP, the highest rate of SLB was desquamative interstitial pneumonia/respiratory bronchiolitis-interstitial lung disease (DIP/RB-ILD, 10/10), lymphoid interstitial pneumonia (LIP, 9/9), followed by cryptogenic organizing (COP, 18/26), nonspecific interstitial pneumonia (NSIP, 22/53), IPF (43/395), UIIP (13/285). CONCLUSIONS: IPF was the most common ILDs in our ILD center, followed by IPAF, CTD-ILD and UIIP. Histological information may help to establish diagnostic algorithm in ILD.