Role of KL-6 in evaluating the disease severity of rheumatoid lung disease: comparison with HRCT

Rheumatoid Arthritis-Associated Interstitial Lung Disease (RA-ILD): Update on Prevalence, Risk Factors, Pathogenesis, and Therapy

PURPOSE OF REVIEW

Rheumatoid arthritis is frequently complicated by interstitial lung disease (RA-ILD), an underappreciated contributor to excess morbidity and mortality. The true prevalence of RA-ILD is difficult to define given the variability in diagnostic criteria used. The lack of standardized screening methods, an incomplete understanding of disease pathogenesis, and dearth of validated biomarkers have limited the development of controlled clinical trials for this disease.

RECENT FINDINGS

Numerous studies have focused on clinical, radiographic, genetic, molecular, and/or serologic markers of disease severity as well as risk of disease progression. In addition to defining valuable clinical biomarkers, these studies have provided insights regarding the pathogenesis of RA-ILD and potential therapeutic targets. Additional studies involving immunomodulatory and/or anti-fibrotic agents have assessed new therapeutic options for different stages of RA-ILD. RA-ILD continues to be a major contributor to the increased morbidity and mortality associated with RA. Advancements in our understanding of disease pathogenesis at a molecular level are necessary to drive the development of more targeted therapy.

Cohort study of serological biomarkers for interstitial lung disease in patients with rheumatoid arthritis

OBJECTIVE

Interstitial lung disease (ILD) is an important cause of mortality in patients with rheumatoid arthritis (RA). Early RA-ILD detection is essential to improve prognosis. Here, we investigated eight serological biomarkers that may contribute to RA-ILD detection.

METHOD

Fifty-five patients from the Early Rheumatoid Arthritis Program were evaluated for ILD with high-resolution computed tomography (HRCT) and pulmonary function tests (PFTs) using the SCAPIS protocol. Blood samples were obtained for biomarker analysis, and patients' clinical records were reviewed. We defined ILD using five different models based on the measurements used to confirm ILD: Model A = HRCT; B = PFTs; C = A plus B; D = C plus symptoms; and E = D plus inhalations.

RESULTS

Among 55 patients, two had an ILD diagnosis before the study, but over one-third fulfilled the ILD criteria. Cancer antigen 15-3 (CA15-3) and matrix metalloproteinase-7 (MMP-7) differentiated between RA with and without ILD (all p < 0.05). Surfactant protein D (SP-D) showed similar trends, as did macrophage inflammatory protein-1β (MIP-1β) and chitinase 3-like protein-1 (YKL-40). Based on Pearson's correlation coefficients, MIP-1β and YKL-40 were significantly correlated with DAS28 (MIP-1β: 0.3; YKL-40: 0.4), ESR (MIP-1β: 0.3; YKL-40: 0.4), and CRP (only MIP-1β: 0.4) (all p < 0.05). CA15-3 was correlated with rheumatoid factor and anti-citrullinated peptide antibodies (Pearson's correlation 0.3; both p = 0.03).

CONCLUSIONS

CA15-3 was the most significant biomarker for ILD detection in RA patients with stable low disease activity, closely followed by MMP-7. SP-D, MIP-1β, and YKL-40 may also contribute to RA-ILD diagnosis.

Correlation between CT-based phenotypes and serum biomarker in interstitial lung diseases

BACKGROUND

The quantitative analysis of computed tomography (CT) and Krebs von den Lungen-6 (KL-6) serum level has gained importance in the diagnosis, monitoring, and prognostication of interstitial lung disease (ILD). However, the associations between quantitative analysis of CT and serum KL-6 level remain poorly understood.

METHODS

In this retrospective observational study conducted at tertiary hospital between June 2020 and March 2022, quantitative analysis of CT was performed using the deep learning-based method including reticulation, ground glass opacity (GGO), honeycombing, and consolidation. We investigated the associations between CT-based phenotypes and serum KL-6 measured within three months of the CT scan. Furthermore, we evaluated the performance of the combined CT-based phenotypes and KL-6 levels in predicting hospitalizations due to respiratory reasons of ILD patients.

RESULTS

A total of 131 ILD patients (104 males) with a median age of 67 years were included in this study. Reticulation, GGO, honeycombing, and consolidation extents showed a positive correlation with KL-6 levels. [Reticulation, correlation coefficient (r) = 0.567, p < 0.001; GGO, r = 0.355, p < 0.001; honeycombing, r = 0.174, p = 0.046; and consolidation, r = 0.446, p < 0.001]. Additionally, the area under the ROC of the combined reticulation and KL-6 for hospitalizations due to respiratory reasons was 0.810 (p < 0.001).

CONCLUSIONS

Quantitative analysis of CT features and serum KL-6 levels ascertained a positive correlation between the two. In addition, the combination of reticulation and KL-6 shows potential for predicting hospitalizations of ILD patients due to respiratory causes. The combination of reticulation, focusing on phenotypic change in lung parenchyma, and KL-6, as an indicator of lung injury extent, could be helpful for monitoring and predicting the prognosis of various types of ILD.

Association of Serum Krebs von den Lungen-6 (KL-6) Levels and Disease Severity in Patients Hospitalized with COVID-19

Objective

We aimed to evaluate Krebs von den Lungen-6 (KL-6) as a possible biomarker in determining disease severity in patients with moderate and severe COVID-19.

Materials and Methods

This cross-sectional study included moderate or severe COVID-19 patients; critically ill patients who were followed up in the intensive care unit were not included. KL-6 level and routine laboratory test measurements were performed on the first day of admission. The patients were also categorized according to their hyperinflammatory state.

Results

The study included 92 patients, 56 (61%) women. The National Institutes of Health (NIH) score was 2 in 52.2% of the patients and 3 in 47.8%. KL-6 levels did not significantly differ in disease severity (NIH score 2 vs. 3; p=0.15). Median KL-6 values were 52.7 (29.1) in patients with <2 COVID-19 hyperinflammatory syndrome score (cHIS) and 61.7 (32.2) in patients with cHIS ≥ 2 (p= 0.077). KL-6 values tended to be higher among the patients with lower lymphocyte counts, but the difference was not statistically significant (<1000 mm³/L p=0.006 and higher cHIS scores ≥2 p=0.07). KL-6 values were also higher in the patients with diabetes mellitus compared to the remaining patients (p =0.036).

Conclusion

There was no significant association between the serum KL-6 measured at admission and the severity of COVID-19.

Understanding Interstitial Lung Diseases Associated with Connective Tissue Disease (CTD-ILD): Genetics, Cellular Pathophysiology, and Biologic Drivers

Connective tissue disease-associated interstitial lung disease (CTD-ILD) is a collection of systemic autoimmune disorders resulting in lung interstitial abnormalities or lung fibrosis. CTD-ILD pathogenesis is not well characterized because of disease heterogeneity and lack of pre-clinical models. Some common risk factors are inter-related with idiopathic pulmonary fibrosis, an extensively studied fibrotic lung disease, which includes genetic abnormalities and environmental risk factors. The primary pathogenic mechanism is that these risk factors promote alveolar type II cell dysfunction triggering many downstream profibrotic pathways, including inflammatory cascades, leading to lung fibroblast proliferation and activation, causing abnormal lung remodeling and repairs that result in interstitial pathology and lung fibrosis. In CTD-ILD, dysregulation of regulator pathways in inflammation is a primary culprit. However, confirmatory studies are required. Understanding these pathogenetic mechanisms is necessary for developing and tailoring more targeted therapy and provides newly discovered disease biomarkers for early diagnosis, clinical monitoring, and disease prognostication. This review highlights the central CTD-ILD pathogenesis and biological drivers that facilitate the discovery of disease biomarkers.

Krebs von den lungen-6 as a clinical marker for hypersensitivity pneumonitis: A meta-analysis and bioinformatics analysis

Aim

Hypersensitivity pneumonitis (HP), also referred to as exogenous allergic alveolitis, is one of the most common interstitial lung diseases (ILDs). A potential immune biomarker, Krebs von den lgen-6 (KL-6) characterizes the progression and severity of HP. The meta-analysis in this study was conducted to elucidate the variations in the concentrations of KL-6 in different types of HP.

Methods

A systematic search of various databases such as EMBASE, Pubmed, CNKI, VIP, Web of Science, and WanFang was carried out to find relevant published articles between January 1980 and August 2022 that explored the relationship between KL-6 and allergic pneumonia. Standardized mean difference (SMD) and 95% confidence interval (CI) were used as effect sizes for comparison among different groups. The GSE47460 and GSE150910 datasets were downloaded to extract and validate the differences in KL-6 mRNA expression between HP lung tissue and healthy controls. Furthermore, the single-cell sequencing dataset GSE135893 was downloaded to extract KL-6 mRNA expression in type II alveolar epithelial cells to validate the differences between HP and healthy controls. Two researchers evaluated the quality of the included studies by employing Newcastle-Ottawa Scale. All the qualified studies were subjected to statistical analyses carried out utilizing RevMan 5.2, Stata 11.0, and R software 4.1.3.

Results

Twenty studies aligned perfectly with the inclusion criteria of the meta. The concentrations of KL-6 were substantially higher in the blood of HP patients as compared to the control group. Subgroup analyses were carried out in accordance with the allergen source and the results revealed that patients with different allergens had higher blood KL-6 concentrations than healthy controls. Additionally, different subgroups of subjects were created for meta-analysis as per the fibrosis status, race, measurement method, and sample type. The concentration of KL-6 in blood was much higher in all HP subgroups than in healthy control groups. Moreover, the bioinformatics analysis revealed that KL-6 mRNA expression was higher in HP lung tissue and type II alveolar epithelial cells as compared to healthy controls.

Conclusion

The present meta-analysis and bioinformatics analysis suggested that the concentration levels of KL-6 varied between HP patients and healthy individuals, and the KL-6 concentrations may be higher in the blood samples of HP patients.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, CRD42022355334.

A genome-wide association study identifying single nucleotide polymorphisms in the PPFIBP2 gene was predictive for interstitial lung disease in rheumatoid arthritis patients

Objective

Genetic polymorphisms might serve as useful prognostic markers for the timely diagnosis of RA. The purpose of this study was to identify genomic factors predictive of the occurrence of interstitial lung disease (ILD) in RA by performing a genome-wide association study of genetic variants, including single nucleotide polymorphisms (SNPs).

Methods

The study population included 306 RA patients. All patients were treated with conventional DMARDs, including 6–16 mg MTX per week. Clinical data and venous blood samples were collected from all patients before administration of DMARDs. A total of 278 347 SNPs were analysed to determine their association with ILD occurrence.

Results

Several SNPs were strongly associated with ILD occurrence (P < 10⁻⁵). rs6578890, which is located on chromosome 11 in the intronic region of the gene encoding tyrosine phosphatase receptor type F polypeptide-interacting protein-binding protein 2 (PPFIBP2), showed the strongest association with ILD occurrence (odds ratio 4.32, P = 10^−7.93).

Conclusion

PPFIBP2 could be a useful genetic marker for occurrence of interstitial pneumonia in RA patients and might help to identify the risk of ILD occurrence before RA treatment, thereby improving patient outcomes.

KL-6 as an Immunological Biomarker Predicts the Severity, Progression, Acute Exacerbation, and Poor Outcomes of Interstitial Lung Disease: A Systematic Review and Meta-Analysis

Object

Interstitial lung disease (ILD) is a specific form of chronic fibrosing interstitial pneumonia with various etiology. The severity and progression of ILD usually predict the poor outcomes of ILD. Otherwise, Krebs von den Lungen-6 (KL-6) is a potential immunological biomarker reflecting the severity and progression of ILD. This meta-analysis is to clarify the predictive value of elevated KL-6 levels in ILD.

Method

EBSCO, PubMed, and Cochrane were systematically searched for articles exploring the prognosis of ILD published between January 1980 and April 2021. The Weighted Mean Difference (WMD) and 95% Confidence Interval (CI) were computed as the effect sizes for comparisons between groups. For the relationship between adverse outcome and elevated KL-6 concentration, Hazard Ratio (HR), and its 95%CI were used to estimate the risk factor of ILD.

Result

Our result showed that ILD patients in severe and progressive groups had higher KL-6 levels, and the KL-6 level of patients in the severe ILD was 703.41 (U/ml) than in mild ILD. The KL-6 level in progressive ILD group was 325.98 (U/ml) higher than that in the non-progressive ILD group. Secondly, the KL-6 level of patients in acute exacerbation (AE) of ILD was 545.44 (U/ml) higher than stable ILD. Lastly, the higher KL-6 level in ILD patients predicted poor outcomes. The KL-6 level in death of ILD was 383.53 (U/ml) higher than in survivors of ILD. The pooled HR (95%CI) about elevated KL-6 level predicting the mortality of ILD was 2.05 (1.50–2.78), and the HR (95%CI) for progression of ILD was 1.98 (1.07–3.67).

Conclusion

The elevated KL-6 level indicated more severe, more progressive, and predicted the higher mortality and poor outcomes of ILD.

Bronchoalveolar lavage and lung biopsy in connective tissue diseases, to do or not to do?

Bronchoalveolar lavage and lung biopsy (LBx) are helpful in patients with connective tissue diseases (CTD) and interstitial lung diseases (ILD) regardless of cause, including infectious, noninfectious, immunologic, or malignant. The decision whether to perform only bronchoalveolar lavage (BAL), and eventually a subsequent LBx in case of a nondiagnostic lavage, or one single bronchoscopy combining both sampling methods depends on the clinical suspicion, on patient’s characteristics (e.g. increased biopsy risk) and preferences, and on the resources and biopsy techniques available locally (e.g. regular forceps versus cryobiopsy). In CTD-ILD, BAL has major clinical utility in excluding infections and in the diagnosis of specific patterns of acute lung damage (e.g. alveolar hemorrhage, diffuse alveolar damage, and organizing pneumonia). LBx is indicated to exclude neoplasm or diagnose lymphoproliferative lung disorders that in CTD patients are more common than in the general population. Defining BAL cellularity and characterizing the CTD-ILD histopathologic pattern by LBx can be helpful in the differential diagnosis of cases without established CTD [e.g. ILD preceding full-blown CTD, interstitial pneumonia with autoimmune features (IPAF)], but the prognostic and theragnostic role of those findings remains unclear. Few studies in the pretranscriptomics era have investigated the diagnostic and prognostic role of BAL and LBx in CTD-ILD, and it is reasonable to hypothesize that future studies conducted applying innovative techniques on BAL and LBx might open new and unexpected avenues in pathogenesis, diagnosis, and treatment approach to CTD-ILD. This is particularly desirable now that a new drug treatment era is emerging, in which we have more than one therapeutic choice (immunosuppressive agents, antifibrotic drugs, and biological agents). We hope that future research will pave the path toward precision medicine providing data for a more accurate ILD-CTD endotyping that will guide the physicians through targeted therapeutic choices, rather than to the approximative approach ‘one drug fits them all’.

Association of Serum Biomarkers With Pulmonary Involvement of Rheumatoid Arthritis Interstitial Lung Disease: From KORAIL Cohort Baseline Data

Objective

The increase in mortality in rheumatoid arthritis (RA) patients with interstitial lung disease (ILD) is well known However, there are few studies on serum markers that can evaluate acute exacerbation or prognosis in RA-ILD patients The purpose of this study was to identify the association between biomarkers and lung lesions in patients with RA-ILD.

Methods

We analyzed 153 patients with serum samples in a prospective, multicenter cohort of Korean RA-ILD patients The serum levels of biomarkers, matrix metalloproteinase (MMP-7), surfactant protein-D (SP-D), and Krebs von den Lungen-6 (KL-6) were measured and correlated with forced vital capacity (FVC), diffusing capacity for carbon monoxide (DLCO) and the results of computed tomography (CT) CT results were interpreted semi-quantitatively according to the extent of lung lesions (grade 1, 0%∼25%; grade 2, 26%∼50%; grade 3, 51%∼75%; grade 4, 76%∼100%).

Results

MMP-7, SP-D, and KL-6 were negatively correlated with FVC (MMP-7, r=-0267, p=0001; SP-D, r=-0250, p=0002; KL-6, r=-0223, p=0006) and DLCO (MMP-7, r=-0404, p<0001; SP-D, r=-0286, p=0001; KL-6, r=-0226, p=0007) In addition, MMP-7, SP-D, and KL-6 tended to increase with higher grades of lung lesions on CT (MMP-7, p=0013; SP-D, p<0001; KL-6, p<0001).

Conclusion

MMP-7, SP-D, and KL-6 can be used to evaluate the functional and anatomical status of lung involvement in the RA-ILD patients.

Natural history and screening of interstitial lung disease in systemic autoimmune rheumatic disorders

Interstitial lung disease (ILD) is a relatively frequent manifestation of systemic autoimmune rheumatic disorders (SARDs), including systemic sclerosis (SSc), rheumatoid arthritis (RA), idiopathic inflammatory myopathies (IIM), systemic lupus erythematosus (SLE), primary Sjögren's syndrome (pSS), and anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitis. Interstitial pneumonia with autoimmune features (IPAF) has been proposed to describe patients with ILD who have clinical or serological findings compatible with SARDs but they are not sufficient for a definite diagnosis. ILD may present with different patterns among patients with SARDs, but most commonly as nonspecific interstitial pneumonia (NSIP), with the exception of RA and ANCA vasculitis that more often present with usual interstitial pneumonia (UIP). The natural history of ILD is quite variable, even among patients with the same SARD. It may present with subclinical features following a slow progressively course or with acute manifestations and clinically significant rapid progression leading to severe deterioration of pulmonary function and respiratory failure. The radiographic pattern of ILD, the extent of the disease, the baseline pulmonary function, the pulmonary function deterioration rate over time and clinical variables related to the primary SARD, such as age, sex and the clinical phenotype, are considered prognostic factors for SARDs-ILD associated with adverse outcomes and increased mortality. Different modalities can be employed for ILD detection including clinical evaluation, pulmonary function tests, high resolution computed tomography and novel techniques such as lung ultrasound and serum biomarkers. ILD may determine the clinical outcome of SARDs, since it is associated with significant morbidity and mortality and therefore screening of patients with SARDs for ILD is of great clinical importance.

The role of lung ultrasound B-lines and serum KL-6 in the screening and follow-up of rheumatoid arthritis patients for an identification of interstitial lung disease: review of the literature, proposal for a preliminary algorithm, and clinical application to cases

Screening and follow-up of interstitial lung disease associated with rheumatoid arthritis (RA-ILD) is a challenge in clinical practice. In fact, the majority of RA-ILD patients are asymptomatic and optimal tools for early screening and regular follow-up are lacking. Furthermore, some patients may remain oligosymptomatic despite significant radiological abnormalities. In RA-ILD, usual interstitial pneumonia (UIP) is the most frequent radiological and pathological pattern, associated with a poor prognosis and a high risk to develop acute exacerbations and infections. If RA-ILD can be identified early, there may be an opportunity for an early treatment and close follow-up that might delay ILD progression and improve the long-term outcome.In connective tissue disease-associated interstitial lung disease (CTD-ILD), lung ultrasound (LUS) with the assessment of B-lines and serum Krebs von den Lungen-6 antigen (KL-6) has been recognized as sensitive biomarkers for the early detection of ILD. B-line number and serum KL-6 level were found to correlate with high-resolution computed tomography (HRCT), pulmonary function tests (PFTs), and other clinical parameters in systemic sclerosis-associated ILD (SSc-ILD). Recently, the significant correlation between B-lines and KL-6, two non-ionizing and non-invasive biomarkers, was demonstrated. Hence, the combined use of LUS and KL-6 to screen and follow up ILD in RA patients might be useful in clinical practice in addition to existing tools. Herein, we review relevant literature to support this concept, propose a preliminary screening algorithm, and present 2 cases where the algorithm was used.

Annual variation rate of KL-6 for predicting acute exacerbation in patients with rheumatoid arthritis-associated interstitial lung disease

OBJECTIVES

This study evaluated the prognostic factors for acute exacerbation (AE), including sequential changes in Krebs von den Lungen-6 (KL-6) levels, in rheumatoid arthritis-associated interstitial lung disease (RA-ILD) patients.

METHODS

This was a retrospective observational study. We reviewed 125 patients diagnosed with RA-ILD between 2010 and 2019. We defined ΔKL-6 as the annual variation rate of KL-6 one visit before AE onset (or the last visit). The Cox regression analysis was used for evaluating significant variables associated with AE. We analysed the overall survival and respiratory-related death-free survival.

RESULTS

Thirty-three patients (26.4%) developed AE during the observation period. The univariate analysis revealed that KL-6 levels at RA-ILD diagnosis [hazard ratio (HR), 1.11; 95% confidence interval (CI), 1.05-1.15; p < .01) and ΔKL-6 (HR: 3.69; 95% CI: -1.36 to 7.96; p = .01] were significantly associated with AE. ΔKL-6 was an independent prognostic factor for AE in the multivariate analysis (HR: 3.37; 95% CI: -1.16 to 8.87; p = .03). Patients with AE had a significantly higher overall mortality rate (p = .02) and respiratory-related mortality rate (p < .01) than those without AE.

CONCLUSION

ΔKL-6 can be a prognostic marker for detecting AE in RA-ILD patients.

Serum Krebs von den Lungen-6 level predicts disease progression in interstitial lung disease

Disease progression (DP) in interstitial lung disease (ILD) is variable and difficult to predict. In previous reports, serum Krebs von den Lungen-6 (KL-6) was suggested to be useful in diagnosing and predicting survival in ILD. The aim of our study was to investigate the usefulness of serum KL-6 as a predictor of DP in ILD. Clinical data of 199 patients with ILD (idiopathic pulmonary fibrosis: 22.8%) were prospectively collected and serum KL-6 levels were measured. DP was defined as a relative decline in forced vital capacity (FVC) ≥ 10%, acute exacerbation, or death during follow-up. The median follow-up period was 11.1 months. The mean age of the subjects was 62.2 years, and 59.8% were male. DP occurred in 21.6% of patients. The progressed group showed lower FVC, lower diffusing capacity for carbon monoxide, lower the minimum oxygen saturation during the 6-minute walk test, higher fibrosis scores on high-resolution computed tomography, and higher KL-6 levels (826.3 vs. 629.0 U/mL; p < 0.001) than those of the non-progressed group. In receiver operating characteristic curve analysis, serum KL-6 levels were a significant predictor of DP in ILD (area under the curve = 0.629, p = 0.009, and the optimal cut-off level was 811 U/mL). In multivariable Cox analysis, high serum KL-6 levels (≥ 800 U/mL) were only independently associated with DP in ILD (HR 2.689, 95% CI 1.445–5.004, P = 0.002). Serum KL-6 levels might be useful to predict DP in patients with ILD.

Improving risk-stratification of rheumatoid arthritis patients for interstitial lung disease

OBJECTIVE

To determine the performance of 3 circulating markers for the diagnosis and the progression of interstitial lung disease (ILD) associated with rheumatoid arthritis (RA).

METHODS

Serum concentrations of 3 circulating markers, lung epithelial-derived surfactant protein D (SPD), chemokine CCL-18 and Krebs von den Lungen-6 glycoprotein (KL-6), were measured by ELISA in consecutive patients with established RA. These patients were recruited from 3 tertiary centers and they all had been investigated by chest high-resolution computed tomography (HRCT). For a subset of French patients, a follow-up HRCT was available (mean interval between HRCT: 3±1.5 years).

RESULTS

Among the 147 included patients (age: 66 ± 12 years, 69% women, disease duration 11 ± 10 years), 40 (27%) had RA-ILD on chest HRCT. SPD, CCL18 and KL-6 concentrations were significantly higher in patients with RA-ILD. ROC curve analysis to assess the diagnostic abilities of the three markers for the diagnosis of RA-ILD showed a superiority of KL-6 (Area under the curve, AUC: 0.79 95% CI 0.72-0.86) compared to SPD (AUC: 0.66 95% CI 0.58-0.74) and CCL18 (AUC: 0.62, 95% CI 0.53-0.70). The sensitivity of KL-6 for the diagnosis of RA-ILD was 68% with a specificity of 83%. The combination of KL-6 with SPD and CCL18 improved its diagnostic ability, with increased sensitivity from 68% to 77%, specificity from 83% to 97%. Increased KL-6 levels were independently associated with the presence of RA-ILD after the adjustment on other RA-ILD risk factors. In the French subset with longitudinal data, baseline KL-6 serum levels were predictive of ILD progression and the degree of ILD progression on HRCT was proportional to baseline KL-6 concentrations.

CONCLUSION

These results show that KL-6 is a relevant circulating marker for the diagnosis and might be an interesting marker for the progression of RA-ILD.

Comparative diagnostic efficacy of serum Krebs von den Lungen-6 and surfactant D for connective tissue disease-associated interstitial lung diseases: A meta-analysis

PURPOSE

The aim of the study was to estimate and compare the diagnostic accuracy of serum Krebs von den Lungen-6 (KL-6) and surfactant protein D (SP-D) for identifying interstitial lung disease (ILD) from non-ILD among connective tissue disease (CTD) patients.

MATERIALS AND METHODS

Original articles on the diagnostic accuracy of serum KL-6 and SP-D in differentiating CTD-ILD from CTD-nonILD were identified from three public databases. The overall quality of evidence and methodologic quality of each eligible study were assessed by the Grading of Recommendations, Assessment, Development and Evaluation approach and Quality Assessment of Diagnostic Accuracy Studies, respectively. We used the bivariate model to calculate random-effect sensitivity, specificity, likelihood ratios, and area under curve. Furthermore, trial sequential analysis (TSA) was used to determine whether sample sizes incorporated in the meta-analysis were powerful for evaluating the diagnostic utility. Bayesian network analysis was performed to compare the diagnostic accuracy of 2 serum biomarkers in differentiating ILD among CTD patients and various subgroups.

RESULTS

Twenty-nine studies were included in the quantitative synthesis. No threshold effects were observed (all P values >.05). For diagnosis of ILD among CTD patients, overall sensitivity and specificity of serum KL-6 were 0.76 (95% confidence interval [CI]: 0.68-0.82) and 0.89 (95% CI: 0.83-0.93), whereas those for serum SP-D were 0.65 (95% CI: 0.45-0.80) and 0.88 (95% CI: 0.80-0.93). Comprehensive comparison of 2 circulating biomarkers using back-calculated likelihood ratio (LR) demonstrated that serum KL-6 corresponded to a higher LR+ and a lower LR- in comparison to serum SP-D, as well as in SSc-ILD. TSA indicated that evidence for serum KL-6 and SP-D in identifying CTD-ILD is powerful; nonetheless, more trials were needed for validation of serum KL-6 and SP-D in differentiating CTD-ILD subtypes, including different CTD and ethnicities.

CONCLUSIONS

This meta-analysis suggested that serum KL-6 had superior diagnostic accuracy to SP-D for differentiating ILD from non-ILD among CTD patients, providing a convenient and non-invasive approach for screening and management of ILD among CTD patients.

Prognostic role of blood KL-6 in rheumatoid arthritis-associated interstitial lung disease

Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) has a variable clinical course for which predicting prognosis is difficult. However, the role of blood biomarkers in RA-ILD is ill-defined. The aim of this study was to investigate the prognostic value of Krebs von den Lungen-6 (KL-6) levels in RA-ILD patients. The medical records of 84 patients with RA-ILD were retrospectively reviewed. Plasma KL-6 levels were measured by Nanopia KL-6 assay (SEKISUI MEDICAL, Tokyo), using latex-enhanced immunoturbidimetric assay. The median follow-up period was 61 months. Mean age was 61.4 years, 45.2% were men, 44.0% were ever-smokers, and 35.7% showed a usual interstitial pneumonia (UIP) pattern on high-resolution computed tomography. The median KL-6 level at baseline was 741.2 U/mL (interquartile range, 439.7-1308.9 U/mL). On multivariate logistic regression analysis, a high KL-6 level (≥ 640 U/mL) was an independently associated with a UIP pattern (odds ratio [OR], 5.173; P = 0.005) with old age (OR, 1.104, P = 0.005). On multivariate Cox analysis, a high KL-6 level (≥ 685 U/mL) was an independent prognostic factor for the mortality (hazard ratio [HR], 2.984; P = 0.016) with a older age (HR, 1.061; P = 0.030), male sex (HR, 3.610; P = 0.001), lower forced vital capacity (HR, 0.957; P = 0.002), and a UIP pattern (HR, 4.034; P = 0.002). Our results suggest that high KL-6 levels might be useful as a biomarker for the presence of a UIP pattern and prognosis in patients with RA-ILD.

Anti-carbamylated proteins antibody repertoire in rheumatoid arthritis: evidence of a new autoantibody linked to interstitial lung disease

OBJECTIVE

To analyse the association between anti-carbamylated protein antibodies (Anti-CarP) and interstitial lung disease (ILD) in rheumatoid arthritis (RA) patients.

METHODS

Cross-sectional study including RA patients fulfilling the 2010 ACR/EULAR criteria. The main population comprised two groups: (1) RA patients diagnosed with RA-ILD (RA-ILD group); (2) RA patients without ILD (non-ILD RA group). Non-ILD RA patients in whom ILD was suspected underwent a diagnostic work-up and, if ILD was diagnosed, were switched to the RA-ILD group. ILD was diagnosed by high-resolution computed tomography and confirmed by a multidisciplinary committee. An independent replication sample was also obtained. Three Anti-CarP IgG autoantibodies against fetal calf serum (Anti-FCS), fibrinogen (Anti-Fib) and chimeric fibrine/filagrine homocitrullinated peptide (Anti-CFFHP) and one Anti-CarP IgA against FCS (Anti-FCS-IgA) were determined by home-made ELISA. Associations between Anti-CarP and ILD were analysed using multivariable logistic regression adjusted by smoking, sex, age, RA disease duration, rheumatoid factor and anticitrullinated protein antibodies.

RESULTS

We enrolled 179 patients: 37 (21%) were finally diagnosed with RA-ILD. Anti-CarP specificities were more frequent in RA-ILD patients (Anti-FCS 70% vs 43%; Anti-Fib 73% vs 51%; Anti-CFFHP 38% vs 19%; Anti-CarP-IgA 51% vs 20%, p<0.05 for all comparisons). Serum titers of Anti-CarP were significantly higher in RA-ILD patients. Anti-CarP specificities showed a robust effect towards increasing the odds of ILD in the multivariate analysis (Anti-FCS (OR: 3.42; 95% CI: 1.13 to 10.40), Anti-Fib (OR: 2.85; 95% CI: 0.83 to 9.70), Anti-CFFHP (OR: 3.11; 95% CI: 1.06 to 9.14) and Anti-FCS-IgA (OR: 4.30; 95% CI: 1.41 to 13.04)). Similar findings were observed in the replication sample.

CONCLUSIONS

Anti-CarP were strongly associated with ILD. The role of homocitrullination in RA-ILD merits further investigation.

Circulating lung biomarkers in idiopathic lung fibrosis and interstitial lung diseases associated with connective tissue diseases: Where do we stand?

Interstitial lung diseases (ILDs) are complex diseases with various courses where personalized medicine is highly expected. Biomarkers are indicators of physiological, pathological processes or of pharmacological response to therapeutic interventions. They can be used for diagnosis, risk-stratification, prediction and monitoring of treatment response. To better delineate the input and pitfalls of biomarkers in ILDs, we performed a systematic review and meta-analysis of literature in MEDLINE and Embase databases from January 1960 to February 2019. We focused on circulating biomarkers as having the highest generalizability. Overall, 70 studies were included in the review and 20 studies could be included in the meta-analysis. This review highlights that ILD associated with connective tissue diseases (CTD-ILD) and idiopathic pulmonary fibrosis (IPF) share common biomarkers, suggesting common pathophysiological pathways. KL-6 and SP-D, could diagnose lung fibrosis in both IPF and CTD-ILD, with KL-6 having the strongest value (OR: 520.95[110.07-2465.58], p<0.001 in IPF and OR:26.43[7.15-97.68], p<0.001 in CTD-ILD), followed by SPD (OR: 33.81[3.20-357.52], p = 0.003 in IPF and 13.24 [3.84-45.71] in SSc-ILD), MMP7 appeared as interesting for IPF diagnosis (p<0.001), whereas in SSc, CCL18 was associated with ILD diagnosis. Both CCL18 and KL-6 were predictive for the outcomes of ILDs, with higher predictive values for CCL18 in both IPF (OR:10.22[4.72-22.16], p<0.001 and in SSc [2.62[1.71-4.03], p<0.001). However, disease specific biomarkers are lacking and large longitudinal studies are needed before the translational use of the potential biomarkers in clinical practice. With the recent availability of new effective therapies in ILDs, further studies should assess response to treatment.

Current Perspectives On Emerging Biomarkers For Rheumatoid Arthritis-Associated Interstitial Lung Disease

Rheumatoid arthritis (RA) is a common systemic autoimmune disease whose fibro-inflammatory manifestations may affect a number of tissues and organs, including the lungs. In fact, interstitial lung disease (ILD) is a leading cause of mortality among patients with RA. RA-related interstitial lung disease (RA-ILD) most often presents in an injury pattern called usual interstitial pneumonia (UIP), which portends a relatively worse prognosis than other less commonly occurring patterns of RA-ILD, like non-specific interstitial pneumonia (NSIP). Biomarkers from serum or bronchoalveolar lavage fluid could aid in the identification of patients at risk for RA-ILD, the detection of patients most likely to develop the UIP pattern of RA-ILD, and the prediction of disease behaviour over time. Notably, the use of highly sensitive serologic biomarkers, including rheumatoid factor (RF) and antibodies targeting cyclic citrullinated peptides, while somewhat specific for RA joint disease, have only limited utility as biomarkers for RA-ILD. Candidate biomarkers for RA-ILD include these and other autoantibodies as well as certain genes and molecules that hold promise as biomarkers in other forms of ILD. In this manuscript, we summarize the state of knowledge on biomarkers for the development and progression of RA-ILD.

Evaluation of changes in the serum levels of Krebs von den Lungen-6 and surfactant protein-D over time as important biomarkers in idiopathic fibrotic nonspecific interstitial pneumonia

BACKGROUND

Some cases of idiopathic fibrotic nonspecific interstitial pneumonia (f-NSIP) show a progressive course that is similar to that of idiopathic pulmonary fibrosis. However, it is difficult to predict poor patient outcomes. This study aimed to evaluate whether serial changes in serum levels of Krebs von den Lungen-6 (KL-6) and surfactant protein-D (SP-D) can predict disease progression.

METHODS

We retrospectively analyzed the medical records of 75 patients with idiopathic f-NSIP. Disease behavior was categorized into two groups depending on long-term change of pulmonary function: progressive type (≥5%/year relative decline in the slope of forced vital capacity [FVC] and/or ≥7.5%/year relative decline in the slope of %diffusing capacity of the lung for carbon monoxide [%D_LCO]) and stable type. Levels of KL-6 and SP-D and results of pulmonary function tests, which were performed parallelly, were reviewed and analyzed using a linear mixed-effects model.

RESULTS

The study subjects comprised 62 patients with stable type and 13 patients with progressive type disease behavior. Among these subjects, 50 patients fulfilled the diagnostic criteria of interstitial pneumonia with autoimmune features (IPAF). Serum levels of both KL-6 and SP-D at baseline showed a negative correlation with %D_LCO, but not with FVC, and these biomarkers were not related to disease progression. Persistently high levels of KL-6 and SP-D correlated with progressive type disease behavior in idiopathic (non-IPAF) f-NSIP.

CONCLUSIONS

Changes in serum KL-6 and SP-D levels over time may provide useful predictive information on disease behavior during treatment in patients with idiopathic f-NSIP and especially in those with non-IPAF f-NSIP.

Malondialdehyde-Acetaldehyde Adducts and Antibody Responses in Rheumatoid Arthritis-Associated Interstitial Lung Disease

OBJECTIVE

To compare serum anti-malondialdehyde-acetaldehyde (anti-MAA) antibody levels and MAA expression in lung tissue from patients with rheumatoid arthritis-associated interstitial lung disease (RA-ILD) to those found in controls.

METHODS

Anti-MAA antibody (IgA, IgM, IgG) concentrations were measured in patients with RA-ILD and compared to those of RA patients with chronic obstructive pulmonary disease (COPD) and RA patients without lung disease. Associations between anti-MAA antibody with RA-ILD were assessed using multivariable logistic regression. Lung tissue from patients with RA-ILD, other ILD, or emphysema, and from controls (n = 3 per group) were stained for MAA, citrulline, macrophages (CD68), T cells (CD3), B cells (CD19/CD27), and extracellular matrix proteins (type II collagen, fibronectin, vimentin). Tissue expression and colocalization with MAA were quantified and compared.

RESULTS

Among 1,823 RA patients, 90 had prevalent RA-ILD. Serum IgA and IgM anti-MAA antibody concentrations were higher in RA-ILD than in RA with COPD or RA alone (P = 0.005). After adjustment for covariates, the highest quartiles of IgA anti-MAA antibody concentration (odds ratio 2.09 [95% confidence interval 1.11-3.90]) and IgM (odds ratio 2.23 [95% confidence interval 1.19-4.15]) were significantly associated with the presence of RA-ILD. MAA expression in RA-ILD lung tissue was greater than in tissue from all other groups (P < 0.001), and it colocalized with citrulline (r = 0.79), CD19+ B cells (r = 0.78), and extracellular matrix proteins (type II collagen [r = 0.72] and vimentin [r = 0.77]) to the greatest degree in RA-ILD.

CONCLUSION

Serum IgA and IgM anti-MAA antibody is associated with ILD among RA patients. MAA is highly expressed in RA-ILD lung tissue, where it colocalizes with other RA autoantigens, autoreactive B cells, and extracellular matrix proteins, highlighting its potential role in the pathogenesis of RA-ILD.

Sequential changes of serum KL-6 predict the progression of interstitial lung disease

Background

Interstitial lung disease (ILD) is a slowly progressing fatal fibrotic lung disease with a widely variable clinical course and a poor prognosis. Clinicians and patients would benefit from a highly efficient and accurate predictor for ILD. The purpose of this study was to evaluate whether blood biomarkers can predict ILD progression.

Methods

In this study, 85 patients diagnosed as having ILD at the Guangzhou Institute of Respiratory Health participated, including 20 patients with idiopathic pulmonary fibrosis (IPF). During the mean follow-up time of 12 months, every patient was examined during four or five visits in our center. Serum samples were collected at baseline, and after 1, 2, 6, and 12 months and tested for the Klebs von den Lungen-6 (KL-6) concentration. Dynamic fluctuations in this biomarker concentration were examined using a logistic regression model to see if they reflected the progression of ILD.

Results

The baseline levels of serum KL-6 in the ILD patients were significantly increased compared to healthy controls. Serum KL-6 levels were significantly elevated in patients with progression of disease (1,985.2±1,497.8 vs. 1,387.6±1,313.1 µg/mL; P<0.001). Logistic regression revealed sequential changes of KL-6 was a significant predictor of ILD progression in the next follow-up (OR, 2.569; 95% CI, 2.260-2.880; P=0.001), and that sequential changes of KL-6 were significant predictors for the progression of IPF (OR, 3.611; 95% CI, 1.048-12.442; P<0.01). Baseline concentrations were not predictive for ILD or IPF. Univariate Cox analysis showed that KL-6 was significantly associated with survival [relative risk (RR), 1.901; 95% CI, 1.294-2.793; P<0.001], along with other variables.

Conclusions

Serum levels of KL-6 were elevated in ILD patients with severe respiratory function compared to those without. The rate of poor prognosis and mortality was associated with increased biomarker concentrations. Sequential measurements of biomarkers could be valuable in disease monitoring and evaluations in clinical management.

Comprehensive review of current diagnostic and treatment approaches to interstitial lung disease associated with rheumatoid arthritis

Interstitial lung disease (ILD) is one of the extra-articular involvement forms of rheumatoid arthritis (RA), and it is associated with increased mortality. The presence of genetic susceptibility, smoking, rheumatoid factor positivity, and the presence of anticitrulline peptide antibodies are factors contributing to the development of ILD in patients with RA. Early diagnosis and treatment of ILD contribute to the reduction of morbidity and mortality. We herein evaluated the current literature for the diagnosis and treatment of RA-associated ILD.

Interstitial lung disease in the connective tissue diseases; a paradigm shift in diagnosis and treatment

Interstitial lung disease (ILD) in the connective tissue diseases (CTD) is amongst the most challenging aspect of care of patients with rheumatic diseases and is the source of significant morbidity and mortality. While there has been progress in our understanding of the natural history of these complications, we still suffer from a limited reservoir of data to confidently determine which patients are at highest risk for disease and those who are at highest risk for disease progression. Treatment options until recently have been limited to anti-inflammatory therapies but with the emerging availability of anti-fibrotic therapies, a shift in strategy is emerging to target therapies based on the specific radiographic, histopathologic features and biomarker profiles that are unique to patients with rheumatic diseases and ILD.

Recent advances in connective tissue disease related interstitial lung disease

INTRODUCTION

Interstitial lung disease (ILD) is a common manifestation of connective tissue disease (CTD). Although the majority of patients with CTD-ILD are stable or slowly progressive, a significant group exhibits a more severe and progressive decline. Interstitial pneumonia with autoimmune features (IPAF) describes the subset of patients with interstitial pneumonia who have features suggesting underlying autoimmunity, but whose features fall short of a clear diagnosis of CTD. Areas covered: In this focused review, we discuss recent advances in early detection, prognostic evaluation, and management of autoimmune forms of ILD. Expert commentary: Early detection of ILD and a better understanding of factors that impact prognostication may be helpful when making decisions regarding therapeutic interventions. The treatment of CTD-ILD should be comprehensive, is often fraught with challenges and can be complicated by comorbid conditions and extra-thoracic disease activities. Several large randomized studies have examined the impact of immunosuppressive therapy for CTD-ILD, however, additional studies are needed to determine the optimal treatment strategies. Future studies may provide additional information about the best treatments in patients with IPAF.

Connective tissue disease-related interstitial lung disease

Interstitial lung disease (ILD) is commonly present in patients with an underlying connective tissue disease (CTD), particularly those with systemic sclerosis, rheumatoid arthritis, and inflammatory myositis. The clinical spectrum can range from asymptomatic findings on imaging to respiratory failure and death. Distinguishing features in the clinical, radiographic, and histopathologic characteristics of CTD-ILD subsets can predict prognosis and treatment response. Treatment often consists of combinations of immunosuppressive medications, but there is a paucity of guidance in the literature to help clinicians determine appropriate screening and management of CTD-ILD. As such, there is a critical need for studies that can elucidate the natural history of the CTD-ILD, as well as clarify optimal therapies for CTD patients with ILD.

Respiratory mechanics measured by forced oscillation technique in rheumatoid arthritis-related pulmonary abnormalities: frequency-dependence, heterogeneity and effects of smoking

Rheumatoid arthritis (RA)-related pulmonary disorders specifically airway abnormalities and interstitial pneumonia (IP) are important extra-articular manifestations. The forced oscillation technique (FOT) is a useful method to assess respiratory impedance, respiratory resistance (Rrs) and reactance (Xrs), at different oscillatory frequencies during tidal breathing. The aim of this study was to characterize the respiratory mechanics of patients with RA and to relate them to parameters of the pulmonary function test and findings of chest CT images. Respiratory impedance of RA patients (n = 69) was measured as a function of frequency from 4 to 36 Hz using the FOT device and compared with that of healthy subjects (n = 10). Data were retrospectively reviewed. Patients were female-dominant (60.9 %) and 95.7 % had abnormal CT findings including airway and parenchymal abnormalities. Thirty-seven of 69 patients (53.6 %) were smokers. Rrs was significantly frequency-dependent in RA patients but not in the healthy subjects. Xrs were significantly frequency-dependent in both RA and healthy groups. Rrs was significantly higher during an expiratory phase in both RA and healthy groups. Xrs was significantly lower (more negative) during an expiratory phase than that during an inspiratory phase in RA patients but not in healthy subjects. Xrs of the RA group was significantly more negative than that of the normal control. There was no difference in impedance parameters between the airway lesion dominant (n = 27) and IP dominant groups (n = 23) in the RA group. The impedance parameters of the RA group significantly correlated with most parameters of the pulmonary function test. In pulmonary function test results, % of the predicted value for forced expiratory flow from 25 to 75 % of forced vital capacity was significantly lower and % of the predicted value for diffusing capacity of the lung for carbon monoxide was higher in the airway lesion dominant group than those in the IP dominant group. Krebs von den Lungen-6, a serum indicator of IP, was significantly higher in the IP group than that in the airway lesion dominant group. Taken together, the impedance results reflect abnormalities in pulmonary functions and structures in patients with RA.

Monitoring of Lung Involvement in Rheumatologic Disease

The monitoring of lung involvement in patients with connective tissue diseases is central to optimal long-term management and is directed towards: (a) the detection of supervening lung involvement not present at presentation and (b) the identification of disease progression in established lung disease. For both goals, accurate surveillance requires multi-disciplinary evaluation with the integration of symptomatic change, serial pulmonary function trends and imaging data. Evaluated in isolation, each of these monitoring domains has significant limitations. Symptomatic change may be confounded by a wide variety of systemic factors. Pulmonary function tests provide the most reliable data, but are limited by measurement variability, the heterogeneity of functional patterns and the confounding effects of non-pulmonary factors. Chest radiography is insensitive to change but may provide rapid confirmation of major disease progression or alert the clinician to respiratory co-morbidities. Although high-resolution computed tomography has a central role in assessing disease severity, it should be used very selectively as a monitoring tool due to the associated radiation burden. Ancillary tests include echocardiography and exercise testing to proactively identify cases of pulmonary hypertension and worsening of oxygenation. In summary, a multi-disciplinary approach is essential for the identification of disease progression and prompt treatment of comorbidities that severely impact on the morbidity and mortality of disease.

Treatment of rheumatoid arthritis-associated interstitial lung disease: a perspective review

Rheumatoid arthritis (RA) is a systemic autoimmune disease affecting 0.5-1% of the worldwide population. Whilst predominantly causing chronic pain and inflammation in synovial joints, it is also associated with significant extra-articular manifestations in a large proportion of patients. Among the various pulmonary manifestations, interstitial lung disease (ILD), a progressive fibrotic disease of the lung parenchyma, is the commonest and most important, contributing significantly to increased morbidity and mortality. The most frequent patterns of RA-associated ILD (RA-ILD) are usual interstitial pneumonia and nonspecific interstitial pneumonia. New insights during the past several years have highlighted the epidemiological impact of RA-ILD and have begun to identify factors contributing to its pathogenesis. Risk factors include smoking, male sex, human leukocyte antigen haplotype, rheumatoid factor and anticyclic citrullinated protein antibodies (ACPAs). Combined with clinical information, chest examination and pulmonary function testing, high-resolution computed tomography of the chest forms the basis of investigation and allows assessment of subtype and disease extent. The management of RA-ILD is a challenge. Several therapeutic agents have been suggested in the literature but as yet no large randomized controlled trials have been undertaken to guide clinical management. Therapy is further complicated by commonly prescribed drugs of proven articular benefit such as methotrexate, leflunomide (LEF) and anti-tumour necrosis factor α agents having been implicated in both ex novo occurrence and acceleration of existing ILD. Agents that offer promise include immunomodulators such as mycophenolate and rituximab as well as newly studied antifibrotic agents. In this review, we discuss the current literature to evaluate recommendations for the management of RA-ILD and discuss key gaps in our knowledge of this important disease.

Serum Krebs von den Lungen-6 level as a diagnostic biomarker for interstitial lung disease in Chinese patients

OBJECTIVES

The purpose of this study was to determine the diagnostic and prognostic values of serum KL-6 levels in Chinese patients with interstitial lung disease (ILDs).

METHODS

A total of 1084 subjects including 373 cases of ILDs, 584 cases of non-ILD pulmonary diseases, and 127 healthy individuals were recruited from three clinical centers in China between January 2011 and December 2013. A total of 106 patients undergoing treatments for ILDs in Shanghai Pulmonary Hospital between January 2011 and December 2013 were enrolled. Baseline and posttreatment serum KL-6 levels were determined.

RESULTS

Serum KL-6 levels in patients with ILDs were significantly higher than those in patients with non-ILD pulmonary diseases or in healthy individuals (1492.09 ± 2230.08 U/mL vs 258.67 ± 268.73 U/mL or 178.73 ± 71.17 U/mL, all P < 0.05). At the cut-off value of 500 U/mL, the sensitivity and specificity of serum KL-6 as a diagnostic marker for ILDs was 77.75% and 94.51%, respectively. The Kappa value was 0.743 (P < 0.001). The area below the receiver operating characteristic curve was 0.922 with a 95% Confidence interval of 0.904-0.941 (P < 0.001). The posttreatment serum KL-6 levels significantly reduced in patients with improved ILDs, whereas markedly increased in patients with exacerbated ILDs (All P < 0.05).

CONCLUSIONS

Serum KL-6 levels might be a promising diagnostic biomarker for ILDs in Chinese patients. The prognostic value of serum KL-6 levels for ILDs remains to be verified by large-scaled studies.

Biomarkers of rheumatoid arthritis-associated interstitial lung disease

OBJECTIVE

Interstitial lung disease (ILD) is a relatively common extraarticular manifestation of rheumatoid arthritis (RA) that contributes significantly to disease burden and excess mortality. The purpose of this study was to identify peripheral blood markers of RA-associated ILD that can facilitate earlier diagnosis and provide insight regarding the pathogenesis of this potentially devastating disease complication.

METHODS

Patients with RA who were enrolled in a well-characterized Chinese identification cohort or a US replication cohort were subclassified as having RA-no ILD, RA-mild ILD, or RA-advanced ILD, based on high-resolution computed tomography scans of the chest. Multiplex enzyme-linked immunosorbent assays (ELISAs) and Luminex xMAP technology were used to assess 36 cytokines/chemokines, matrix metalloproteinases (MMPs), and acute-phase proteins in the identification cohort. Unadjusted and adjusted logistic regression models were used to quantify the strength of association between RA-ILD and biomarkers of interest.

RESULTS

MMP-7 and interferon-γ-inducible protein 10 (IP-10)/CXCL10 were identified by multiplex ELISA as potential biomarkers for RA-ILD in 133 RA patients comprising the Chinese identification cohort (50 RA-no ILD, 41 RA-ILD, 42 RA-indeterminate ILD). The findings were confirmed by standard solid-phase sandwich ELISA in the Chinese identification cohort as well as an independent cohort of US patients with RA and different stages of ILD (22 RA-no ILD, 49 RA-ILD, 15 RA-indeterminate ILD), with statistically significant associations in both unadjusted and adjusted logistic regression analyses.

CONCLUSION

Levels of MMP-7 and IP-10/CXCL10 are elevated in the serum of RA patients with ILD, whether mild or advanced, supporting their value as pathogenically relevant biomarkers that can contribute to noninvasive detection of this extraarticular disease complication.

Interstitial lung disease in rheumatoid arthritis: Current concepts in pathogenesis, diagnosis and therapeutics

Rheumatoid arthritis (RA) is the most common chronic autoimmune inflammatory joint disease. RA-associated interstitial lung disease (RA-ILD) is a major extra-articular complication and causes symptoms that lead to a deterioration in the quality of life, high utilization of health resources, and an increased risk of earlier mortality. Early in the course of RA-ILD, symptoms are highly variable, making the diagnosis difficult. Therefore, a rational diagnostic strategy that combines an adequate clinical assessment with the appropriate use of clinical tests, including pulmonary function tests and high-resolution computed tomography, should be used. In special cases, lung biopsy or bronchioalveolar lavage should be performed to achieve an early diagnosis. Several distinct histopathological subtypes of RA-ILD are currently recognized. These subtypes also have different clinical presentations, which vary in therapeutic response and prognosis. This article reviews current evidence about the epidemiology of RA-ILD and discusses the varying prevalence rates observed in different studies. Additionally, aspects of RA-ILD pathogenesis, including the role of cytokines and other molecules such as autoantibodies, as well as the evidence linking several drugs used to treat RA with lung damage will be discussed. Some aspects of the clinical characteristics of RA-ILD are noted, and diagnostic strategies are reviewed. Finally, this article analyzes current treatments for RA-ILD, including immunosuppressive therapies and biologic agents, as well as other therapeutic modalities. The prognosis of this severe complication of RA is discussed. Additionally, this paper examines updated evidence from studies identifying an association between drugs used for the treatment of RA and the development of ILD.

A roadmap to promote clinical and translational research in rheumatoid arthritis-associated interstitial lung disease

Rheumatoid arthritis (RA) is a systemic inflammatory disorder affecting approximately 1.3 million adults in the United States. Approximately 10% of these individuals with RA have clinically evident interstitial lung disease (RA-ILD), and an additional one-third demonstrate subclinical ILD on chest CT scan. The risk of death for individuals with RA-ILD is three times higher than for patients with RA without ILD, with a median survival after ILD diagnosis of only 2.6 years. Despite the high prevalence and mortality of RA-ILD, little is known about its molecular features and its natural history. At present, we lack a standard validated approach to the definition, diagnosis, risk stratification, and management of RA-ILD. In this perspective, we discuss the importance of clinical and translational research and how ongoing research efforts can address important gaps in our knowledge over the next few years. Furthermore, recommendations are made to design multicenter collaborative studies that will expedite the development of clinical trials designed to decrease the significant morbidity and mortality associated with RA-ILD.

The multifaceted aspects of interstitial lung disease in rheumatoid arthritis

Interstitial lung disease (ILD) is a relevant extra-articular manifestation of rheumatoid arthritis (RA) that may occur either in early stages or as a complication of long-standing disease. RA related ILD (RA-ILD) significantly influences the quoad vitam prognosis of these patients. Several histopathological patterns of RA-ILD have been described: usual interstitial pneumonia (UIP) is the most frequent one, followed by nonspecific interstitial pneumonia (NSIP); other patterns are less commonly observed. Several factors have been associated with an increased risk of developing RA-ILD. The genetic background plays a fundamental but not sufficient role; smoking is an independent predictor of ILD, and a correlation with the presence of rheumatoid factor and anti-cyclic citrullinated peptide antibodies has also been reported. Moreover, both exnovo occurrence and progression of ILD have been related to drug therapies that are commonly prescribed in RA, such as methotrexate, leflunomide, anti-TNF alpha agents, and rituximab. A greater understanding of the disease process is necessary in order to improve the therapeutic approach to ILD and RA itself and to reduce the burden of this severe extra-articular manifestation.

Idiopathic pulmonary fibrosis: the need for early diagnosis

Idiopathic pulmonary fibrosis (IPF), a chronic fibrosing lung disease of a progressive nature and unknown etiology, has the largest epidemiological impact and the worst prognosis among the idiopathic interstitial pneumonias (IIP). Despite the progress in pathogenetic knowledge, many aspects are still dubious, in particular the biomolecular mechanisms activated in the early stages of the disease. Early diagnosis is desirable not only to better define aspects of the natural history of the disease, but also to customize treatment protocols. An early diagnosis of IPF should necessarily be based on the ability to highlight a number of features drawn not only from a careful composition of specific anamnestic data with clinical, functional and radiological parameters, but also from biological markers that, in a proper context, can provide guidance and confirm a clinical-anamnestic suspicion. The identification of specific biomarkers for IPF is a modern and attractive look for the potential clinical implications in terms of diagnosis, prediction of disease progression and prognosis. Biomolecular investigations on IPF were performed selectively on tissue samples, bronchoalveolar lavage (BAL), or blood: nowadays the “multi-omic” approach may allow studying individual constitutional profiles resorting to a series of biomolecular disciplines, the so-called “omics”, which focuses on responses of the entire genomic complex, in line with the current trend to quantitatively analyze the interactions of all components of a biological system. Such refined investigations are an essential base for research now, but they might become a routine in the near future, allowing a more precise classification of patients suffering from a disease of unclear taxonomy.

Phenotypes of Peripheral Blood Lymphocytes and Cytokine Expression in Polymyositis and Dermatomyositis before Treatment and after Clinical Remission

Objective

To investigate peripheral blood lymphocyte subpopulations, particularly helper T (Th) cells and cytokine expression before and after treatment in polymyositis (PM) and dermatomyositis (DM).

Patients and Methods

Ten patients with PM and 15 with DM were enrolled in this study. As a control we used 11 age-matched healthy subjects. We analyzed peripheral blood lymphocytes using flow cytometry. Serum cytokines were determined by enzyme-linked immunosorbent assay.

Results

Th2/Th1 and Th2/Th17 ratios were significantly higher in both PM and DM than in controls and this Th2-predominancy is marked in DM associated with interstitial pneumonia. IL-1β, IL-6 and TGF-β were significantly higher in both PM and DM and IL-4 showed a significant increase in DM when compared to controls. There was no significant correlation between either any lymphocyte subpopulations or serum cytokines and clinical severity markers such as the manual muscle strength test, serum creatine kinase, and the total CT score. Th2/Th17 in both PM and DM, as well as Th2/Th1 in the latter, significantly decreased after clinical remission compared with before treatment.

Conclusions

Th2-predominancy as shown by the increase in Th2/Th1 and Th2/Th17 ratios may suggest active disease in PM/DM but does not reflect clinical severity.

KL-6: a serological biomarker for interstitial lung disease in patients with polymyositis and dermatomyositis

OBJECTIVES

To investigate whether Caucasian patients with polymyositis (PM) or dermatomyositis (DM) and interstitial lung disease (ILD) have elevated serum levels of KL-6 compared with patients without ILD and whether KL-6 could be used as a marker for ILD activity and treatment efficacy of ILD in PM/DM.

DESIGN AND METHODS

Thirty patients with PM/DM (seven with ILD) and 17 age- and sex-matched healthy controls were included in a retrospective, cross-sectional analysis. Twelve patients were followed for longitudinal evaluation. ILD was defined as restrictive lung function impairment with radiographic signs of ILD. Serum KL-6 levels were measured using a sandwich enzyme immunoassay kit. Groups were compared by Mann-Whitney U-test.

RESULTS

PM/DM patients with ILD had significantly higher median serum KL-6 levels compared with those without ILD: 995 (range 533-2318) versus 322 (range 132-1225) U mL(-1) (P = 0.0002). Median serum levels of healthy controls were 225 (range 136-519) U mL(-1) . Serum levels of KL-6 were inversely correlated with percentages of forced expiratory volume in 1 s (FEV1), vital capacity (VC), total lung capacity (TLC), forced VC, diffusing capacity of carbon monoxide (DLco), maximal voluntary ventilation at 40 breaths min(-1) and residual volume (RV). Changes in KL-6 levels showed a significant inverse correlation with changes in percentage FEV1, TLC, DLco and RV. At a cut-off level of 549 U mL(-1) (mean ± 2.5 SD for controls), the sensitivity and specificity for diagnosis of ILD were 83% and 100%, respectively.

CONCLUSION

The level of serum KL-6 may serve as measure of ILD in patients with PM/DM and is a promising biomarker for use in clinical practice to assess clinical response to treatment.

Coadministration of cyclosporin a with prednisolone in acute interstitial pneumonia complicating polymyositis/dermatomyositis

Objective

To investigate clinical effectiveness of prednisolone (PSL) and cyclosporin A (CyA), particularly continuous intravenous administration of the latter, in patients with interstitial pneumonia (IP) associated with polymyositis/dermatomyositis (PM/DM).

Methods

We reviewed the clinical findings and therapeutic outcomes of patients with PM/DM who had received PSL and CyA (PSL + CyA, n = 21 for DM and 2 for PM) or the former alone (n = 12 for DM and 7 for PM). All patients receiving PSL + CyA had active IP.

Results

Fifteen of the 21 DM patients receiving PSL + CyA showed favorable therapeutic outcomes of IP (recovery group), while the remaining 6 died of respiratory failure (death group). Before treatment PaO₂ in room air and %VC were significantly lower, and the total CT score was significantly higher in the death group than in the recovery one. Continuous intravenous administration of CyA was performed in 6 patients for severe IP requiring oxygen therapy, and of these 2 showed complete recovery from it.

Conclusions

Coadministration of PSL and CyA, particularly continuous intravenous infusion of the latter, from the early phase of illness may be a potent therapeutic option for PM/DM patients with decreases in PaO₂ and %VC and/or a high total CT score suggestive of a poor prognosis.

Rheumatoid arthritis-associated interstitial lung disease

Rheumatoid arthritis (RA) is a systemic inflammatory disorder affecting 1% of the US population. Patients can have extra-articular manifestations of their disease and the lungs are commonly involved. RA can affect any compartment of the respiratory system and high resolution computed tomography (HRCT) of the lung is abnormal in over half of these patients. Interstitial lung disease is a dreaded complication of RA. It is more prevalent in smokers, males, and those with high antibody titers. The pathogenesis is unknown but data suggest an environmental insult in the setting of a genetic predisposition. Smoking may play a role in the pathogenesis of disease through citrullination of protein in the lung leading to the development of autoimmunity. Patients usually present in middle age with cough and dyspnea. Pulmonary function testing most commonly shows reduced diffusion capacity for carbon monoxide and HRCT reveals a combination of reticulation and ground glass abnormalities. The most common pattern on HRCT and histopathology is usual interstitial pneumonia (UIP), with nonspecific interstitial pneumonia seen less frequently. There are no large-scale well-controlled treatment trials. In severe or progressive cases, treatment usually consists of corticosteroids with or without a cytotoxic agent for 6 months or longer. RA interstitial lung disease is progressive; over half of patients show radiographic progression within 2 years. Patients with a UIP pattern on biopsy have a survival similar to idiopathic pulmonary fibrosis.

Interstitial lung disease in rheumatoid arthritis

Rheumatoid arthritis (RA) is the most common systemic autoimmune disease in the United States, affecting 1% to 2% of the adult population. Although joints and synovium are the primary targets in this disorder, extra-articular manifestations involving the lungs can lead to significant morbidity and excess mortality. Among the various pulmonary complications that occur in RA, interstitial lung disease (ILD) is the most damaging, with effects ranging from subclinical inflammation/scarring to end-stage pulmonary fibrosis. New insights during the past several years have underscored the epidemiologic impact of clinically/functionally significant RA-associated ILD (RA-ILD) and have begun to identify factors contributing to the pathogenesis of this potentially devastating complication of RA. Despite these advancements, the complexity of RA-ILD and the lack of reliable predictors for disease progression highlight the need for improved biomarker development. Establishing such detailed molecular signatures will ultimately guide the application and timing of therapeutic agents that include immunomodulators as well as newly studied antifibrotic agents.