BACKGROUND: Anti-neutrophil cytoplasmic antibody (ANCA) is a type of autoantibodies associated with vasculitis. ANCA positivity is commonly observed in interstitial lung disease (ILD) patients. 7%-10% of ANCA-positive ILD patients don\'t present any symptoms of systemic vasculitis and are termed ANCA-positive idiopathic interstitial pneumonia (ANCA-IIP). Some researchers propose that ANCA-IIP should be categorized as interstitial pneumonia with autoimmune features (IPAF), although the official ATS/ERS statements exclude ANCA-IIP from this classification. Whether ANCA-IIP should be categorized into the entity of IPAF is still debatable.
METHODS: Patients diagnosed with ANCA-IIP and those with IPAF were analyzed in a retrospective study of ILD. The clinical outcomes were determined through pulmonary function tests (PFTs) after a one-year follow-up, as well as assessing all-cause mortality.
RESULTS: 27 patients with ANCA-IIP and 143 patients with IPAF were analyzed from a cohort of 995 patients with ILD. Patients in the ANCA-IIP group had an older age and a high proportion of males compared to those in the IPAF group. PFT results at baseline were similar between the two groups, except for a better FEV1% in the ANCA-IIP group. Glucocorticoid and immunosuppressive therapy improved pulmonary function in patients with IPAF, but it continued to deteriorate after one year of treatment in the ANCA-IIP group. Furthermore, the all-cause mortality rate was significantly higher in the ANCA-IIP group than in the IPAF group (22.2% vs. 6.3%, P = 0.017).
CONCLUSIONS: The responses to glucocorticoid and immunosuppressive therapy differ between the ANCA-IIP and IPAF groups, leading to divergent prognoses. Therefore, it is inappropriate to classify ANCA-IIP as part of IPAF.

OBJECTIVE: To explore whether cytokines could be potential biomarkers to predict the occurrence of the progressive fibrosis (PF) phenotype among patients with interstitial pneumonia with autoimmune features (IPAF).
METHODS: This study prospectively collected 51 IPAF and 15 idiopathic pulmonary fibrosis (IPF) patients who were diagnosed at the First Affiliated Hospital of Guangzhou Medical University from July 2020 to June 2021. All IPAF patients were followed up for 1 year to assess the development of PF phenotype. Paired bronchoalveolar lavage fluid (BALF) and serum samples were collected at enrolment and analysed for differences in 39 cytokines expression. Principal component analysis (PCA) and cluster analysis were conducted to identify a subgroup of IPAF patients at high risk for developing the PF phenotype. Finally, cytokine differences were compared between subgroups to identify potential biomarkers for PF-IPAF occurrence.
RESULTS: According to the PCA analysis, 81.25% of PF-IPAF patients share overlapped BALF cytokine profiles with IPF. Cluster analysis indicated that IPAF patients in subtype 2 had a higher risk of developing the PF phenotype within 1 year (P = 0.048), characterized by higher levels of CCL2 and CXCL12, and lower lymphocyte proportion (LYM%) in BALF. Elevated levels of BALF CCL2 (>299.16 pg/ml) or CXCL12 (>660.115 pg/ml) were associated with a significantly higher risk of developing PF phenotype within the 1-year follow-up period (P = 0.009, 0.001, respectively).
CONCLUSIONS: PF-IPAF phenotype exhibits similar inflammatory cytokine profiles to IPF. Cytokine CCL2 and CXCL12, and LYM% in BALF serve as potential biomarkers for predicting the PF phenotype in IPAF patients.
BACKGROUND: Register: Qian Han, Website: http://www.chictr.org.cn/showproj.aspx?proj=61619, Registration number: ChiCTR2000040998.

BACKGROUND: Higher detection of interstitial pneumonia with autoimmune features (IPAF), and idiopathic pulmonary fibrosis (IPF), has significant diagnostic and therapeutic implications. Some matrix metalloproteinases (MMPs) have become reliable diagnostic biomarkers in IPAF and IPF in previous studies, yet relevant reliability remains to be recognized.
METHODS: In this study, 36 ILDs patients, including 31 IPAF patients (Mean ± SD, 50.20 ± 5.10 years; 16 [51.6%] females) and five IPF patients (Mean ± SD, 61.20 ± 6.73 years; one [20.0%] females) were retrospectively enrolled. Serial serum samples were collected from patients with IPAF and IPF between January 2019 and December 2020. Notably, Serum MMPs levels were measured by U-PLEX Biomarker Group 1(Human) Multiplex Assays (MSD, USA).
RESULTS: A combination of MMPs and combinatorial biomarkers was strongly associated with clinical subjects in this study (AUC, 0.597 for Stability vs. Improvement and 0.756 for Stability vs. Exacerbation). Importantly, the AUC of MMP-12 reaches 0.730 (p < 0.05, Stability AUC vs. Improvement AUC) while MMP-13 reaches 0.741 (p < 0.05, Stability AUC vs. Exacerbation AUC) showed better performance than other MMPs in two comparisons.
CONCLUSIONS: Clinical risk factors and MMPs are strongly associated with either stratification of the disease of progression of IPAF or in two IPAF and IPF independent cohorts. To our knowledge, this is the first to illustrate that MMP-12 and MMP-13 may be expected to become typical promising biomarkers in Improvement - IPAF and Exacerbation - IPAF, respectively.

OBJECTIVE: Transbronchial lung cryobiopsy (TBLC) has been recently introduced for diagnosing interstitial lung diseases. We aimed to assess the effectiveness and safety of TBLC by identifying the specific patterns of histology in the diagnosis of connective tissue disease-related interstitial lung disease (CTD-ILD) and interstitial pneumonia with autoimmune features (IPAF).
METHODS: The clinical-radiological-pathological data from the Affiliated Hospital of Guilin Medical University between July 1, 2017, and October 31, 2020, of patients whose clinical-radiological or clinical-radiological-pathological diagnosis was CTD-ILD or IPAF and who underwent TBLC, transbronchial lung biopsy (TBLB), or surgical lung biopsy were retrospectively analyzed and summarized with review. The size of biopsy samples, complications, and diagnostic yield were compared.
RESULTS: Fourteen patients met the inclusion criteria, of whom 12 underwent TBLC, 1 underwent TBLB, and 1 underwent each procedure at different times. Compared to the size of TBLB specimens (5.625 ± 0.479 mm2), the size of TBLC specimens (12.00 (12.00, 15.00) mm2) was much larger (Z = - 3.262, P = 0.001). The diagnostic yields of TBLC and TBLB were 100.00% (13/13) and 0.00% (2/2), respectively (P = 0.0095). The most frequent complication was mild bleeding. The risk of bleeding between TBLB (1/2, 50.00%) and TBLC (10/13, 76.92%) did not differ significantly (P = 0.469).
CONCLUSIONS: TBLC can add extra diagnostic value by effectively identifying specific types of histology for patients with suspected CTD-ILD or IPAF, with a procedure that is safe from adverse events. Key Points • Transbronchial lung cryobiopsy has been introduced recently for diagnosing interstitial lung disease. • Transbronchial lung cryobiopsy was found to be effective and safe in the diagnosis for patients with suspected interstitial lung disease. It can be used as a preferred method for biopsy when the clinical-radiological diagnosis is uncertain.

BACKGROUND: Some patients with interstitial pneumonia with autoimmune features (IPAF) showed a progressive course despite therapy. This study aimed to evaluate whether serial changes in the serum levels of surfactant protein-A (SP-A) and Krebs von den Lungen-6 (KL-6) can predict disease progression.
METHODS: Sixty-four patients with IPAF and 41 patients with non-fibrotic lung disease (non-FLD) were examined. Based on long-term changes in lung function, 36 IPAF patients who were followed up for more than 3 months were divided into a progressive group (n = 9), an improvement group (n = 13), and a stable group (n = 14). Serum KL-6 and SP-A levels were measured. The sensitivity, specificity, cut-off value, and area under the curve (AUC) value for each of the indices were determined using receiver operating characteristic (ROC) curve analysis. The expression differences in these biomarkers and their correlation with disease severity were analyzed.
RESULTS: Compared with non-FLD patients, serum SP-A and KL-6 levels in IPAF patients were increased significantly [SP-A: (p < 0.001); KL-6: (p < 0.001)] and negatively correlated with DLCO (SP-A: rS = - 0.323, p = 0.018; KL-6: rS = - 0.348, p = 0.0011). In patients with progressive disease, the posttreatment serum SP-A and KL-6 levels were increased significantly compared with pretreatment levels [SP-A: (p = 0.021); KL-6: (p = 0.008)]. In patients showing improvement, the levels were decreased significantly [SP-A (p = 0.007) and KL-6 (p = 0.002)]. Changes in serum biomarkers (Delta SP-A and Delta KL-6) were significantly negatively correlated with changes in lung function (Delta FVC, Delta DLCO and Delta FEV1) (rS = 0.482, p < 0.05). A significant positive correlation was found between Delta SP-A and Delta KL-6 (rS = 0.482, p < 0.001).
CONCLUSIONS: Serum SP-A and KL-6 offer high sensitivity and specificity for the diagnosis of IPAF. The decrease in serum SP-A and/or KL-6 levels in patients with IPAF is related to the improvement in pulmonary function. SP-A and KL-6 may be important biomarkers for predicting disease progression in patients with IPAF.

OBJECTIVE: The clinical characteristics of interstitial pneumonia with autoimmune features (IPAF) and connective tissue disease interstitial lung disease (CTD-ILD) have not been adequately compared. We compared the clinical characteristics of these two conditions and analyzed the changes in lung function before and after treatment of IPAF.
METHODS: A total of 412 patients were enrolled in the study, and their clinical characteristics were assessed. The treatment-related changes in 12 cases of IPAF were analyzed.
RESULTS: Complete clinical data were available for 126 patients with CTD-ILD and 147 with IPAF. All IPAF patients showed autoantibody positivity. The proportion of patients showing extrapulmonary symptoms in the CTD-ILD group was higher than that in the IPAF group (P < 0.05). Patients with IPAF demonstrated lower P(A-a)O2 and higher PaO2 and PaCO2 than those with CTD-ILD (P < 0.05 for all comparisons). Forced vital capacity (FVC) and diffusing capacity of the lungs for carbon monoxide (DLCO) in IPAF patients were higher than those in CTD-ILD patients (P = 0.023 for FVC; P = 0.011 for DLCO). Among patients with IPAF, only the proportions of honeycombing and nodules were lower than those in CTD-ILD patients (P < 0.05). Both FVC and DLCO values increased after treatment in patients with IPAF (P < 0.05).
CONCLUSIONS: IPAF showed autoantibody positivity and similar computed tomography (CT) findings as CTD-ILD, and lung function in patients with IPAF improved after immunosuppressive treatment, indicating that IPAF should receive attention and early immunosuppressive treatment like CTD-ILD, even though IPAF exhibits no extrapulmonary symptoms. Key Points • Clinical characteristics of IPAF.

OBJECTIVE: This retrospective clinical study aimed to examine the similarities and differences between connective tissue disease-associated interstitial lung disease (CTD-ILD) and interstitial pneumonia with autoimmune features (IPAF) and to identify the influencing factors of CTD-ILD, with a goal of early detection and active treatment of the disease.
METHODS: We conducted a retrospective study of 480 patients: 412 with CTD-ILD and 68 with IPAF. Demographic features, clinical characteristics, laboratory indicators, and chest high-resolution computed tomography (HRCT) imaging data were analyzed.
RESULTS: Compared with the IPAF group, the CTD-ILD group contained more women, and the incidences of joint pain, dry mouth/dry eyes, and Raynaud\'s phenomenon were higher; erythrocyte sedimentation rate (ESR) and D-dimer levels were higher; red blood cell (RBC) and hemoglobin (Hb) levels were lower; a high rheumatoid factor (RF) titer (> 2 times the normal upper limit) was observed, and anti-cyclic citrullinated peptide antibody (anti-CCP), anti-keratin antibody (AKA), antinuclear antibody (ANA), and anti-melanoma differentiation-associated gene 5 antibody (anti-MDA5) levels were higher. Compared with CTD-ILD patients, IPAF patients were more likely to present initially with respiratory symptoms, with higher rates of fever, cough and expectoration, dyspnea, and Velcro crackles; anti-Ro52 titers were higher; incidences of honeycombing opacity, reticulate opacity, patchy opacity, and pleural thickening were greater. Female sex, a high RF titer (> 2 times the normal upper limit), anti-CCP positivity, ANA positivity, and anti-MDA5 positivity were risk factors for CTD-ILD when the odds ratios were adjusted.
CONCLUSIONS: CTD-ILD and IPAF patients differed in demographic features, clinical characteristics, laboratory indicators, and chest HRCT imaging data. Female sex, a high RF titer (> 2 times the normal upper limit), anti-CCP positivity, ANA positivity, and anti-MDA5 positivity were risk factors for CTD-ILD.Key Points• This retrospective clinical study comprehensively compared the demographic features, clinical characteristics, laboratory indicators, and chest HRCT imaging data of CTD-ILD and IPAF patients.• The evidence suggested that female sex, a high RF titer, anti-CCP positivity, ANA positivity, and anti-MDA5 positivity were risk factors for CTD-ILD.

To investigate the clinical features, risk factors and outcomes of patients with interstitial pneumonia with autoimmune features (IPAF). A total of 1429 patients with idiopathic interstitial pneumonia (IIP) and undifferentiated connective tissue disease-associated interstitial lung disease (UCTD-ILD) were screened to identify patients who met IPAF criteria. Clinical, serological, and morphological features of patients with IPAF were characterized. Outcomes between patients with IPAF, UCTD-ILD, and IIP who were divided into idiopathic pulmonary fibrosis (IPF) and non-IPF groups were compared using survival as an endpoint. Patients with IPAF were much common in young female and had lower percentage of ever smoking and a significantly shorter survival than those with non-IPAF (P < 0.001). Subgroup analysis revealed that IPAF cohort survival was worse than that in non-IPF (P < 0.001), but better than that in IPF (P < 0.001). In IPAF cohort, the most common systemic symptom and serological abnormality were Raynaud\'s phenomenon (12.9%) and ANA ≥ 1:320 (49.2%); the most frequent high-resolution computed tomography (HRCT) pattern was nonspecific interstitial pneumonia (NSIP) (61.6%). Multivariate analysis indicated that several factors including age, smoking history, organizing pneumonia (OP) pattern in HRCT, and anti-RNP positivity were independently associated with significantly worse survival. IPAF had the distinct clinical features and outcomes compared with other groups of ILD. Additional studies should be needed to explore the underlying autoimmune mechanism and to determine risk stratification in future clinical research.