Study design and population
A case–control study of HCs and patients with silicosis and asbestosis was conducted using commercially available enzyme-linked immunosorbent assay (ELISA) to detect the plasma concentrations of CCL18, CXCL13, OPN, periostin, and fibulin-3. All participants underwent chest X-ray, chest high-resolution computed tomography (HRCT), and pulmonary function test.
Over approximately two years (from January 2018 to December 2019), patients from the Department of Occupational Medicine and Toxicology, Beijing Chao-Yang Hospital, were inducted into the study. A total of 231 and 163 outpatients had been recently diagnosed with silicosis and asbestosis, respectively. They were diagnosed according to the radiological criteria of pneumoconiosis based on the 2011 International Labour Organization (ILO) classification.23 Patients with bronchial asthma, tuberculosis, pneumonia, autoimmune diseases, liver or kidney dysfunction, and malignant tumors were excluded. The HCs group comprised 118 age-, sex-, and body mass index (BMI)-matched healthy volunteers from the health examination center of Beijing Chao-yang Hospital during the same time period.
The smoking status of all patients was carefully determined, and they were categorized as non-smokers, ex-smokers (had quit smoking ≥12 months before the study period[A1] ), and smokers (currently smoking or had quit smoking <12 months before the study period). Cigarette smoking is shown by pack-years.
This study was approved by the Institutional Ethics Committee for Human Research, Beijing Chao-Yang Hospital, Capital Medical University, China. Written informed consent was obtained from all the participants involved in the research.
Occupational dust exposure
All the patients provided information on their occupational histories through a standardized questionnaire. The 231 silicosis patients were local residents who had been exposed to silica dust during the processing of jade (71, 30.7%), excavation and digging (68, 29.4%), mining and quarrying (49, 21.2%), sand blasting (13, 5.6%), and raw material handling (30, 12.9%). The 163 asbestosis patients were local residents who had been exposed to chrysotile dust or fibers; among them, 127 (77.9%) and 36 (22.1%) patients were exposed to asbestos products during textile production and in a working atmosphere (e.g., heat insulation workers and boiler maintenance workers), respectively.
Evaluation of CCL18, CXCL13, OPN, periostin, and fibulin-3 concentrations
The plasma samples were collected from each participant and stored at −80°C for analysis. All samples were measured within two weeks of storage. The plasma concentrations of CCL18, CXCL13, and OPN were measured using commercially available human ELISA kits (R&D Systems, Inc., Minneapolis, MN, USA), with a sensitivity of 1.77 pg/mL, 3.97pg/mL, and 0.024ng/ml, respectively. The plasma periostin concentrations were measured using commercially available ELISA kits (Bluegene, Shanghai, China) with a sensitivity of 10 pg/mL. The plasma fibulin-3 concentrations were measured using commercially available ELISA kits (Abcam, Waltham, USA) with a sensitivity of 0.63 ng/mL.
Pulmonary function test
Pulmonary function tests were carried out by certified technicians according to the hospital guidelines, which met the recommendations of the American Thoracic Society (ATS)/European Respiratory Society (ERS).24 Pulmonary function parameters were measured using spirometry, whole body plethysmography, and single-breath diffusing capacity for carbon monoxide (DLCO SB) measurements.
HRCT Scan
HRCT scans of patients were performed with 0.625-mm sections, a 1-s scan time, and a 10-mm interval in the apex basescans with the inclusion of both lungs in the field of view.
Statistical analysis
Data are expressed as mean±standard deviation and/or interquartile range, and the differences among the three groups were analyzed using the Kruskal–Wallis test or one-way analysis of variance. The differences among the two groups were evaluated using t test. Counting data were analyzed using the chi-square test. Correlations between parameters were assessed using Pearson’s correlation coefficient. The levels of plasma biomarkers were further analyzed by a receiver operating characteristic (ROC) curve to determine the cut-off levels that resulted in the optimal diagnostic accuracy for each marker between the patients and controls. These cut-off levels were used to determine the sensitivity and specificity. A P value of < 0.05 was considered statistically significant. Statistical analyses were performed using GraphPad Prism 6 (GraphPad Software Inc, SanDiego, CA, USA) and SPSS Statistics version 23 (IBM Inc, Chicago, IL, USA).