Background Interstitial lung disease (ILD) is a common pulmonary complication of connective tissue disease (CTD). This study aims to evaluate the clinical diagnostic value of matrix metalloproteinase-9 (MMP-9), surfactant protein-D (SP-D), and vascular endothelial growth factor (VEGF) as potential biomarkers for CTD-ILD. Methods This research included 33 CTD-ILD patients, 31 CTD patients without ILD, and 24 healthy control subjects. Then, the value of biomarkers for the diagnosis and evaluation of CTD-ILD was assessed through high-resolution computed tomography (HRCT) findings and pulmonary function test (PFT) parameters. Results The serum MMP-9, SP-D, and VEGF levels in the CTD-ILD group were higher than those in the CTD-NILD group and healthy group. The ROC curve indicates that VEGF has good to excellent diagnostic performance in diagnosing CTD-ILD, the cut-off that best optimizes sensitivity and specificity in diagnosing CTD-ILD is 277.60 pg/ml (sensitivity, 87.9%; specificity, 83.6%), with an area under the curve (AUC) of 0.905 (95% confidence interval (CI) 0.842–0.968); The ROC curve for MMP-9 suggests this biomarker is fair for diagnosis of CTD-ILD(sensitivity, 81.8%; specificity, 81.8%), with an AUC of 0.867 (95% CI 0.784–0.950), but SP-D only provided lower specificity with higher sensitivity in diagnosing CTD-ILD(sensitivity, 90.9%; specificity, 40.0%). The different serum biomarkers are more specific and sensitive when combined to diagnose ILD. The semiquantitative score for the degree of ILD severity on HRCT was positively correlated with SP-D and VEGF levels (r = 0.461, P = 0.007; r = 0.362, P = 0.039), and serum MMP-9 levels were elevated in the UIP subgroup compared to the non-UIP subgroup. The percentage of diffusing capacity of the lung for carbon monoxide (DLco) (% predicted) had a negative correlation with the SP-D level (r = − 0.407, P = 0.044) and a statistically negative correlation between MMP-9 and the forced vital capacity (FVC) (r = − 0.451, P = 0.024). Conclusions Serum MMP-9, SP-D, and VEGF levels may have clinical value in screening and evaluating the severity of CTD-ILD.

Background Numerous studies have described the critical importance of interleukin (IL) ‐36γ in host defense against lung infections, but it is unknown whether it plays a role in infectious pleural effusion (IPE). This study aimed to examine the levels of IL‐36γ in pleural effusions of different etiologies and evaluate the diagnostic accuracy of IL‐36γ in the differential diagnosis of IPE. Methods A total of 112 individuals was enrolled in this research. IL‐36γ levels in pleural fluids of all 112 patients were measured by enzyme‐linked immunosorbent assay (ELISA). We also characterized these markers' diagnostic values across various groups. Results Patients with tuberculous pleural effusion (TPE) and parapneumonic effusion (PPE) had exhibited markedly higher IL‐36γ levels in their pleural fluid than the malignant pleural effusion (MPE) and transudative effusion patients. Furthermore, the IL‐36γ concentrations in TPE patients were evidently higher than in uncomplicated parapneumonic effusion (UPPE) patients but significantly lower than in complicated parapneumonic effusion (CPPE)/empyema patients. Pleural fluid IL‐36γ is a useful marker to differentiate TPE from UPPE, at a cut‐off value for 657.5 pg/ml (area under the curve = 0.904, p < 0.0001) with 70.0% sensitivity and 95.7% specificity. Conclusions The elevated IL‐36γ in pleural effusion may be used as a novel biomarker for infectious pleural effusion diagnosis, particularly in patients with CPPE/empyema, and is a potentially promising biomarker to differentiate between TPE and UPPE.

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