Introduction:
Interstitial lung disease (ILD) is a common complication of connective tissue disease (CTD), which seriously affects the prognosis of patients. The abnormal expression of tumor markers in non-neoplastic diseases may be related to the occurrence and development of CTD-ILD. This study aimed to explore the detailed clinical characteristics of CTD-ILD, and to analyze its internal correlation with serum tumor markers.

Material and methods:
The clinical data of 128 patients with CTD-ILD were retrospectively analyzed. 79 of ILD patients without CTD were enrolled as the non-combined group. Clinical data included imaging manifestations, laboratory indexes and tumor markers such as carbohydrate antigen (CA) 125, CA153, carcinoembryonic antigen (CEA), neuron-specific enolase (NSE) and squamous cell carcinoma (SCC) antigen were collected. ROC curve was used to analyze the clinical value.

Results:
The proportion of clinical manifestations such as arthralgia, rash, Raynaud’s phenomenon, dry mouth and dry eyes in the combined group was higher than the non-combined group (P < 0.05). The serum albumin and total protein levels in the combined group were lower than the non-combined group (P < 0.001). The levels of CA125, CA153, CEA, SCC and NSE in the combined group were higher than the non-combined group (P < 0.001). The AUC of combined detection of each index was 0.917, with a sensitivity of 97.47% and a specificity of 76.56%.

Conclusions:
The main clinical manifestations for CTD-ILD patients were arthralgia, rash, Raynaud’s phenomenon, dry mouth and eyes. The combined detection of tumor markers had a high evaluation value.