Detection of interstitial pneumonitis in patients with rheumatoid arthritis by measuring circulating levels of KL-6, a human MUC1 mucin

Serum VEGF-A levels on admission in COVID-19 patients correlate with SP-D and neutrophils, reflecting disease severity: A prospective study

BACKGROUND AND OBJECTIVE

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in significant global morbidity and mortality. This study aimed to investigate the clinical significance of serum vascular endothelial growth factor A (VEGF-A) in COVID-19 patients and its association with disease severity and pulmonary injury.

METHODS

We prospectively collected data from 71 hospitalized COVID-19 patients between June 2020 and January 2021. Patients were classified as either mild or severe based on their oxygen requirements during hospitalization. Serum VEGF-A levels were measured using an ELISA kit.

RESULTS

In comparison to mild cases, significantly elevated serum VEGF-A levels were observed in severe COVID-19 patients. Furthermore, VEGF-A levels exhibited a positive correlation with white blood cell count, neutrophil count, and lymphocyte count. Notably, serum surfactant protein-D (SP-D), an indicator of alveolar epithelial cell damage, was significantly higher in patients with elevated VEGF-A levels.

CONCLUSION

These results suggest that elevated serum VEGF-A levels could serve as a prognostic biomarker for COVID-19 as it is indicative of alveolar epithelial cell injury caused by SARS-CoV-2 infection. Additionally, we observed a correlation between VEGF-A and neutrophil activation, which plays a role in the immune response during endothelial cell injury, indicating a potential involvement of angiogenesis in disease progression. Further research is needed to elucidate the underlying mechanisms of VEGF-A elevation in COVID-19.

Associations of the Serum KL-6 with Severity and Prognosis in Patients with Acute Exacerbation of Chronic Obstructive Pulmonary Disease

BACKGROUND

As a biomarker of alveolar-capillary basement membrane injury, Krebs von den Lungen-6 (KL-6) is involved in the occurrence and development of pulmonary diseases. However, the role of the KL-6 in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) has yet to be elucidated. This prospective study was designed to clarify the associations of the serum KL-6 with the severity and prognosis in patients with AECOPD.

METHODS

This study enrolled 199 eligible AECOPD patients. Demographic data and clinical characteristics were recorded. Follow-up was tracked to evaluate acute exacerbation and death. The serum KL-6 concentration was measured via an enzyme-linked immunosorbent assay.

RESULTS

Serum KL-6 level at admission was higher in AECOPD patients than in control subjects. The serum KL-6 concentration gradually elevated with increasing severity of AECOPD. Pearson and Spearman analyses revealed that the serum KL-6 concentration was positively correlated with the severity score, monocyte count and concentrations of C-reactive protein, interleukin-6, uric acid, and lactate dehydrogenase in AECOPD patients during hospitalization. A statistical analysis of long-term follow-up data showed that elevated KL-6 level at admission was associated with longer hospital stays, an increased risk of future frequent acute exacerbations, and increased severity of exacerbation in COPD patients.

CONCLUSION

Serum KL-6 level at admission is positively correlated with increased disease severity, prolonged hospital stay and increased risk of future acute exacerbations in COPD patients. There are positive dose-response associations of elevated serum KL-6 with severity and poor prognosis in COPD patients. The serum KL-6 concentration could be a novel diagnostic and prognostic biomarker in AECOPD patients.

Periostin Is a Biomarker of Rheumatoid Arthritis-Associated Interstitial Lung Disease

Periostin was investigated as a biomarker for rheumatoid arthritis-associated interstitial lung disease (RA-ILD). This prospective study measured serum monomeric and total periostin, Klebs von den Lungen-6 (KL-6), surfactant protein D (SP-D), and lactate dehydrogenase (LDH) in 19 patients with RA-ILD, 20 RA without ILD, and 137 healthy controls (HC). All biomarkers were higher in RA-ILD than HC or RA without ILD. KL-6 accurately detected ILD in RA patients (area under curve [AUC] = 0.939) and moderately detected SP-D and monomeric and total periostin (AUC = 0.803, =0.767, =0.767, respectively). Monomeric and total periostin were negatively correlated with normal lung area and positively correlated with honeycombing, reticulation, fibrosis score, and the traction bronchiectasis grade but not inflammatory areas. Serum levels of SP-D, KL-6, and LDH did not correlate with the extent of those fibrotic areas on high-resolution CT. Serum monomeric and total periostin were higher in patients with RA-ILD with definite usual interstitial pneumonia pattern compared with other ILD patterns. Immunohistochemical analyses of biopsy or autopsy lung tissues from RA-ILD during the chronic phase and acute exacerbation showed that periostin was expressed in fibroblastic foci but not inflammatory or dense fibrosis lesions. Periostin is a potential biomarker for diagnosis, evaluating fibrosis, and deciding therapeutic strategies for patients with RA-ILD.

Serum biomarkers of remodeling in severe asthma with fixed airway obstruction and the potential role of KL-6

Over 3% of asthmatic patients are affected by a particularly severe form of the disease ("severe asthma", SA) which is often refractory to standard treatment. Airway remodeling (AR), which can be considered a critical characteristic of approximately half of all patients with SA and currently thought to be the main mechanism triggering fixed airway obstruction (FAO), seems to be a key factor affecting a patient's outcome. Despite the collective efforts of internationally renowned experts, to date only a few biomarkers indicative of AR and no recognizable biomarkers of lung parenchymal remodeling have been identified. This work examines the pathogenesis of airway and lung parenchymal remodeling and the serum biomarkers that may be able to identify the severe asthmatic patients who may develop FAO. The study also aims to examine if Krebs von den Lungen-6 (KL-6) could be considered a diagnostic biomarker of lung structural damage in SA.

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.

KL-6 as a Biomarker of Interstitial Lung Disease Development in Patients with Sjögren Syndrome: A Retrospective Case–Control Study

Objective

Krebs von den Lungen-6 (KL-6) is expressed on regenerating type II pneumocytes and has been recognized as biomarkers in interstitial lung disease (ILD). We aim to identify the role of the serum KL-6 level in patients with newly diagnosed Sjögren syndrome (SS), as well as the correlation between the immunoassays.

Methods

Patients with newly diagnosed SS and receiving HRCT for clinical reason during follow-up were included. Baseline KL-6 level was measured via enzyme-linked immunosorbent assay (ELISA) and latex particle-enhanced turbidimetric immunoassay (LETIA).

Results

Of the 39 patients, 21 (53.85%) developed interstitial lung disease (ILD) by the conclusion of the follow-up period. The median time to diagnosis of ILD was 2.24 years (IQR 1.15–4.34) in the ILD group. The median serum KL-6 level, measured using ELISA, was 1232 U/mL (IQR 937–2242) and 764.5 U/mL (IQR 503.25–1035.75) in the ILD group and the non-ILD group, respectively (p = 0.001). The median LETIA for serum KL-6 was 329 U/mL (IQR 235–619) and 245 U/mL (IQR 215.25–291) in the ILD group and the non-ILD group, respectively (p = 0.074).

Conclusion

Serum KL-6 levels were higher in newly diagnosed SS patients with ILD diagnosis during follow-up. Thus, the serum KL-6 level can serve as a valuable biomarker to identify hidden ILD in patients with newly diagnosed SS patients. However, the immunoassay procedure may influence the efficacy of the prediction and its clinical association.

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’.

Krebs von den Lungen-6 (KL-6) is a pathophysiological biomarker of early-stage acute hypersensitivity pneumonitis among pigeon fanciers

BACKGROUND

Identifying early stages of hypersensitivity pneumonitis (HP) is hampered by variable presentation, heterogeneous or undetected causal antigens and lack of gold-standard biomarkers. Krebs von den Lungen (KL)-6 is pathophysiological biomarker of alveolar epithelial damage. Pigeon fanciers, susceptible to HP, provide a model to investigate early HP.

OBJECTIVE

To test the hypothesis that plasma concentrations of KL-6 are increased in early-stage acute HP.

METHODS

Clinical history, spirometry and blood samples were obtained from pigeon fanciers, 20 with intermittent acute symptoms indicative of developing HP, 27 with no symptoms and 10 healthy subjects with no avian exposure. Plasma KL-6 (units/mL) and pigeon antigen-specific IgG antibody were quantified by enzyme immunoassay. Blood lymphocytes were quantified by flow cytometry and antigen specificity by in vitro cytokine production.

RESULTS

KL-6 was higher in fanciers than controls, median (IQR) 452 (244, 632) vs 274 (151, 377), P = .01. Although fanciers with symptoms had similar antigen exposure and lung function, they had higher KL-6 than those without, 632 (468, 1314) vs 320 (200, 480), P < .001. KL-6 correlated with IgG antibody titre in those with symptoms, r = .591, P = .006. High KL-6, irrespective of symptom category, was associated with higher antibody (P = .006) and lymphocyte proliferation (P = .041), and lower CD4+ T lymphocyte proportion (P = .032).

CONCLUSION AND CLINICAL RELEVANCE

Raised KL-6 is associated with acute symptoms of early-stage HP, and its correlation with antibody may support therapeutic strategies when HP is suspected. KL-6 may act as a mechanistic biomarker of early pathogenesis by linking lung pathophysiological changes with an endotype of immune hypersensitivity.

Azathioprine for Connective Tissue Disease-Associated Interstitial Lung Disease

BACKGROUND

Immunosuppressive therapy still is the standard treatment for patients with connective tissue disease-associated interstitial lung disease (CTD-ILD).

OBJECTIVES

This retrospective study aimed to provide data on the tolerability and efficacy of azathioprine in progressive CTD-ILDs.

METHODS

A total of 56 patients with CTD-ILD treated with azathioprine between 2003 and 2014 were included in the study. The patients were assessed every 3 months during follow-up.

RESULTS

The mean treatment duration was 34 months, with a range of 3-105 months. Fifteen patients (27%) discontinued treatment due to side effects, mostly due to elevated liver enzymes, within the first 3 months. Forty-one patients were treated for longer than 3 months, and 27 of those (66%) had stabilization or improvement of pulmonary function during treatment. In patients who remained stable or improved, the mean FVC was 62 ± 17% predicted (% pred) at initiation of treatment and 65 ± 17% pred at the last follow-up visit (p = 0.036), and the mean DLCO was 38 ± 16% pred at initiation of treatment and 39 ± 17% pred at the last follow-up visit (p = 0.06).

CONCLUSIONS

Azathioprine can stabilize or improve CTD-ILD. While early drug intolerance is frequent, most patients who have tolerated the drug well achieve long-term stabilization or improvement of lung function.

Krebs von den Lungen-6 as a biomarker for disease severity assessment in interstitial lung disease: a comprehensive review

Aim: Interstitial lung diseases (ILD) are a group of lung disorders characterized by interstitial lung thickening. Krebs von den Lungen-6 (KL-6) is a molecule that is predominantly expressed by damaged alveolar type II cells and it has been proposed as a potential biomarker of different ILD. Materials & methods: A growing literature about KL-6 has been reviewed and selected to evaluate its role in the clinical management of ILD to predict disease diagnosis, activity, prognosis and treatment response. Results: KL-6 concentrations have been evaluated in fibrotic and granulomatous lung diseases and it was demonstrated to be a biomarker of disease severity useful for clinical follow-up of ILD patients. KL-6 levels differentiated between fibrotic ILD, such as idiopathic pulmonary fibrosis and chronic hypersensitivity pneumonitis, and nonfibrotic lung disorders, including sarcoidosis and pulmonary alveolar proteinosis. Conclusion: KL-6 is predictive biomarker useful in the clinical management of ILD patients, in particular in patients with severe fibrotic lung disorders.

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.

Protective and predictive role of Mucin1 in sepsis-induced ALI/ARDS

OBJECTIVE

We aimed to investigate whether inhibition of MUC1 would aggravate sepsis-induced ALI, and explore the predictive value of plasma MUC1 for sepsis patients with or without ARDS.

MATERIALS AND METHODS

MUC1 siRNA pre-treatment was used to knockdown MUC1 expression in vitro. GO203 was used to inhibit the homodimerization of MUC1-C in vivo. Expression levels of MUC1, TLR 4 and HIF-1α were detected by Western blot. In addition, plasma MUC1 levels of enrolled patients were detected by ELISA on the day of admission and on the 3rd day. ROC curve was used to determine the predictive value of MUC1 in sepsis patients with ARDS.

RESULTS

Our results showed that inhibition of MUC1 could aggravate sepsis-induced acute lung injury and increase the expression of inflammatory cytokines in sera and BALF of sepsis mice. At the same time, we confirmed that inhibition of MUC1 could significantly decrease HIF-1α expression and thereby activate the expression level of TLR4. HIF-1α was a negative regulator of TLR-4. In addition, plasma MUC1 levels of sepsis patients with ARDS were significantly higher than those without ARDS and healthy adults. ROC curve showed that predictive value of plasma MUC1 on sepsis with ARDS on the 3rd day of enrollment was higher than the day of enrollment.

CONCLUSION

MUC1 could inhibit the expression of TLR-4 by stabilizing HIF-1α, thereby alleviate sepsis-induced lung injury and protect organ function. At the same time, elevated MUC1 levels in plasma had a good predictive valud on whether patients with sepsis would develop ARDS.

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.

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.

Interleukin-18 is associated with the presence of interstitial lung disease in rheumatoid arthritis: a cross-sectional study

OBJECTIVE

Serum interleukin-18 (IL-18) levels are increased in patients with interstitial lung disease (ILD). In addition, IL-18 levels are increased in patients with rheumatoid arthritis (RA) and are associated with arthritis activity. We determined whether increased IL-18 levels are associated with ILD in RA.

METHOD

RA patients were enrolled using an RA cohort database. Plasma IL-18 levels were measured by enzyme-linked immunosorbent assay. ILD was determined by a pulmonologist and a radiologist based on chest radiography and computed tomography findings. IL-18 levels for RA with ILD and RA without ILD were compared. Associations between ILD and various markers including IL-18 and confounding factors (e.g. smoking history) were investigated by logistic regression analysis. Diagnostic values of IL-18 for the presence of ILD were investigated using receiver operating characteristics curve analysis.

RESULTS

ILD was complicated in 8.2% (n = 26) of the study population (N = 312). Plasma IL-18 levels were higher for RA patients with ILD than for RA patients without ILD (721.0 ± 481.4 vs 436.8 ± 438.9 pg/mL, p < 0.001). IL-18, Krebs von den Lungen-6, and anti-cyclic citrullinated peptide antibody titre and glucocorticoid doses were independently associated with the presence of ILD during multivariate logistic regression analysis. Sensitivity and specificity of IL-18 levels for the detection of ILD in RA patients were 65.3% and 76.3%, respectively (area under the curve = 0.73).

CONCLUSION

Plasma IL-18 levels were higher for RA patients with ILD than for those without ILD. Increased IL-18 levels were associated with the presence of ILD.

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.

Up-to-Date Information on Rheumatoid Arthritis-Associated Interstitial Lung Disease

Pulmonary involvement is common in rheumatoid arthritis (RA) and affects all the components of the lung. Interstitial lung disease (ILD) is the most predominant pulmonary manifestation and has been identified as the main cause of morbidity and mortality in RA. Clinically significant RA-ILD occurs in approximately 10% of RA patients. Several risk factors, such as old age, male gender, and smoking, have been reported to date. Histologically, the proportion of the usual interstitial pneumonia (UIP) pattern is higher in RA-ILD than in ILD associated with other connective tissue diseases, and RA-ILD also shows nonspecific interstitial pneumonia and organizing pneumonia patterns. High-resolution computed tomography scans are highly predictive of the histological UIP pattern with a specificity of 96%–100%. Acute exacerbation, which is the acute deterioration of the respiratory status characterized by newly developed bilateral infiltrates with unknown etiologies, has been reported in RA-ILD. Although acute exacerbation of RA-ILD has high mortality, similar to that of idiopathic pulmonary fibrosis, its incidence is lower in RA-ILD than in idiopathic pulmonary fibrosis. A consensus treatment has not yet been established. Current therapeutic regimens typically include corticosteroids with or without cytotoxic agents. Recent large longitudinal studies reported that the prognosis of RA-ILD was poor with a median survival of 2.6–3.0 years. Furthermore, histological and/or radiological patterns, such as UIP or non-UIP, have significant prognostic implications. RA-ILD patients with histological or radiological UIP patterns have poorer prognoses than those with non-UIP patterns. This review assessed the characteristics of RA-ILD by overviewing recent studies in the field and focused on the clinical significance of histological and/or radiological patterns in 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.

Efficacy and safety of mavrilimumab in subjects with rheumatoid arthritis

Objectives

Mavrilimumab, a human monoclonal antibody targeting the alpha subunit of the granulocyte-macrophage colony-stimulating factor receptor, was evaluated in a phase 2 randomised, double-blind, placebo-controlled study to investigate efficacy and safety in subjects with rheumatoid arthritis (RA).

Methods

Subcutaneous mavrilimumab (10 mg, 30 mg, 50 mg, or 100 mg) or placebo was administered every other week for 12 weeks in subjects on stable background methotrexate therapy. The primary endpoint was the proportion of subjects achieving a ≥1.2 decrease from baseline in Disease Activity Score (DAS28-CRP) at week 12.

Results

55.7% of mavrilimumab-treated subjects met the primary endpoint versus 34.7% placebo (p=0.003) at week 12; for the 10 mg, 30 mg, 50 mg, and 100 mg groups, responses were 41.0% (p=0.543), 61.0% (p=0.011), 53.8% (p=0.071), and 66.7% (p=0.001) respectively. Response rate differences from placebo were observed at week 2 and increased throughout the treatment period. The 100 mg dose demonstrated a significant effect versus placebo on DAS28-CRP<2.6 (23.1% vs 6.7%, p=0.016), all categories of the American College of Rheumatology (ACR) criteria (ACR20: 69.2% vs 40.0%, p=0.005; ACR50: 30.8% vs 12.0%, p=0.021; ACR70: 17.9% vs 4.0%, p=0.030), and the Health Assessment Questionnaire Disability Index (−0.48 vs −0.25, p=0.005). A biomarker-based disease activity score showed a dose-dependent decrease at week 12, indicating suppression of disease-related biological pathways. Adverse events were generally mild or moderate in intensity. No significant hypersensitivity reactions, serious or opportunistic infections, or changes in pulmonary parameters were observed.

Conclusions

Mavrilimumab induced rapid clinically significant responses in RA subjects, suggesting that inhibiting the mononuclear phagocyte pathway may provide a novel therapeutic approach for RA.

Elevation of KL-6 serum levels in clinical trials of tumor necrosis factor inhibitors in patients with rheumatoid arthritis: a report from the Japan College of Rheumatology Ad Hoc Committee for Safety of Biological DMARDs

OBJECTIVE

The associations between elevated levels of serum Krebs von den Lungen-6 (KL-6) and treatment of rheumatoid arthritis (RA) with tumor necrosis factor (TNF) inhibitors were investigated in five Japanese clinical trials.

METHODS

Percentages and incidence rates were calculated for elevated serum KL-6 levels. Adverse events associated with elevated levels of serum KL-6 were investigated.

RESULTS

In RISING, a clinical trial for infliximab, 15.6 % of the enrolled patients met criterion B (KL-6 ≥500 U/ml and >1.5-fold increase over the baseline value) by week 54. In HIKARI, 7.8 % of the certolizumab pegol (CZP) group and 0 % of the placebo group met criterion B during the double-blind (DB) period (p = 0.003). In J-RAPID, 8.4 % of the methotrexate (MTX) + CZP and 3.9 % of the MTX + placebo groups met criterion B during the DB period. In GO-MONO, 1.8 % of the golimumab (GLM) and 1.3 % of the placebo groups met criterion B during the DB period. In GO-FORTH, 7.1 % of the MTX + GLM and 0 % of the MTX + placebo groups met criteron B during the DB period (p = 0.017). No adverse events accompanied the elevation of serum KL-6 levels in 95.7 % of these patients.

CONCLUSION

Serum KL-6 levels may increase during anti-TNF therapy without significant clinical events. In these patients, continuing treatment with TNF inhibitors under careful observation is a reasonable option.

A retrospective study of serum KL-6 levels during treatment with biological disease-modifying antirheumatic drugs in rheumatoid arthritis patients: a report from the Ad Hoc Committee for Safety of Biological DMARDs of the Japan College of Rheumatology

OBJECTIVE

We investigated associations between treatment with methotrexate (MTX) or biological disease-modifying antirheumatic drugs (DMARDs) and elevation of serum Krebs von den Lungen-6 (KL-6) levels in Japanese patients with rheumatoid arthritis (RA).

METHODS

Using a standardized form, data were collected retrospectively from medical records and analyzed descriptively.

RESULTS

Of a total of 198 RA patients with KL-6 serum levels measured at initiation of treatment (month 0) and two or more times by month 12, 27 (17.9 %) of 151 RA patients treated with biological DMARDs, including infliximab, etanercept, adalimumab, and tocilizumab (the biological DMARDs group), and 5 (10.6 %) of 47 patients treated without biological DMARDs but with MTX (MTX group), met criterion B (max. KL-6 ≥500 U/ml and >1.5-fold from baseline) by 12 months. The majority of patients (n = 28) meeting criterion B had no apparent interstitial lung disease or malignancy. Of these 28 patients, 21 had serum KL-6 levels available after reaching their maximum level, and 13 (61.9 %) of the 21 then met criterion R [decrease to less than 500 U/ml or to less than (baseline + 0.5 × (maximum - baseline))] by month 12.

CONCLUSION

Serum KL-6 levels may increase during treatment with MTX or these biological DMARDs without significant clinical events.

Patterns of interstitial lung disease during everolimus treatment in patients with metastatic renal cell carcinoma

OBJECTIVE

To elucidate the patterns of interstitial lung disease during everolimus treatment in patients with metastatic renal cell carcinoma, we reviewed seven cases of everolimus-induced interstitial lung disease.

METHODS

Seven patients with metastatic renal cell carcinoma, which continued to progress despite treatment with sunitinib or sorafenib, developed interstitial lung disease after treatment with everolimus.

RESULTS

Chest X-ray demonstrated diffuse infiltrates in lung fields, and chest computed tomography showed bilateral reticular and ground-glass opacities. Serum levels of lactate dehydrogenase (7/7), C-reactive protein (6/7), pulmonary surfactant associated protein D (1/7) and Krebs von den Lungen 6 (5/7) were elevated. The bronchoalveolar lavage fluid obtained from four patients with Grade 3 interstitial lung disease showed lymphocytosis. The transbronchial lung biopsy specimens showed interstitial lymphocytic infiltration and septal thickening of alveolar walls. In two cases with mild interstitial lung disease, the everolimus therapy was successfully continued. In four cases with Grade 3 interstitial lung disease, the drug was discontinued and steroid therapy was initiated. Pulmonary symptoms and radiological abnormalities resolved within 2 months.

CONCLUSIONS

Serum Krebs von den Lungen 6 was elevated compared with baseline in all cases with interstitial lung disease. Some patients who developed mild interstitial lung disease during everolimus treatment could continue to receive the treatment. Even when severe interstitial lung disease developed, withdrawal of the drug and short-term use of high-dose steroids resulted in rapid recovery. Prompt recognition of interstitial lung disease exacerbation as well as exclusion of progressive disease or infection is of primary importance.

Utility of KL-6/MUC1 in the clinical management of interstitial lung diseases

Interstitial lung diseases (ILDs) are a diverse group of pulmonary disorders characterized by various patterns of inflammation and fibrosis in the interstitium of the lung. Because injury and/or regeneration of type II pneumocytes are prominent histological features of ILDs, substances derived from type II pneumocytes have been the focus of research investigating potential biomarkers for ILD. One important biomarker for ILD is the high-molecular-weight glycoprotein, Krebs von den Lungen-6 (KL-6). KL-6 is now classified as a human MUC1 mucin protein, and regenerating type II pneumocytes are the primary cellular source of KL-6/MUC1 in the affected lungs of patients with ILD. KL-6/MUC1 is detectable in the serum of patients with ILD, and extensive investigations performed primarily in Japan have revealed that serum KL-6/MUC1 is elevated in 70-100% of patients with various ILDs, including idiopathic interstitial pneumonias, collagen vascular disease-associated interstitial pneumonia, hypersensitivity pneumonia, radiation pneumonitis, drug-induced ILDs, acute respiratory distress syndrome, pulmonary sarcoidosis, and pulmonary alveolar proteinosis. The results from these various studies have supported the utility of KL-6/MUC1 as a serum biomarker for detecting these various ILDs. Moreover, KL-6/MUC1 serum levels have been demonstrated to be useful for evaluating disease activity and predicting the clinical outcomes of various ILD types. Based on these observations, we believe that KL-6/MUC1 is currently one of the best and most reliable serum biomarkers available for ILD management.

KL-6 concentration in pulmonary epithelial lining fluid is a useful prognostic indicator in patients with acute respiratory distress syndrome

BACKGROUND

KL-6 is a mucin-like glycoprotein expressed on the surface of alveolar type II cells. Elevated concentrations of KL-6 in serum and epithelial lining fluid (ELF) in patients with acute respiratory distress syndrome (ARDS) have been previously reported; however, kinetics and prognostic significance of KL-6 have not been extensively studied. This study was conducted to clarify these points in ARDS patients.

METHODS

Thirty-two patients with ARDS who received mechanical ventilation under intubation were studied for 28 days. ELF and blood were obtained from each patient at multiple time points after the diagnosis of ARDS. ELF was collected using a bronchoscopic microsampling procedure, and ELF and serum KL-6 concentrations were measured.

RESULTS

KL-6 levels in ELF on days 0 to 3 after ARDS diagnosis were significantly higher in nonsurvivors than in survivors, and thereafter, there was no difference in concentrations between the two groups. Serum KL-6 levels did not show statistically significant differences between nonsurvivors and survivors at any time point. When the highest KL-6 levels in ELF and serum sample from each patient were examined, KL-6 levels in both ELF and serum were significantly higher in nonsurvivors than in survivors. The optimal cut-off values were set at 3453 U/mL for ELF and 530 U/mL for serum by receiver operating characteristic (ROC) curve analyses. Patients with KL-6 concentrations in ELF higher than 3453 U/mL or serum concentrations higher than 530 U/mL had significantly lower survival rates up to 90 days after ARDS diagnosis.

CONCLUSIONS

ELF and serum KL-6 concentrations were found to be good indicators of clinical outcome in ARDS patients. Particularly, KL-6 levels in ELF measured during the early period after the diagnosis were useful for predicting prognosis in ARDS patients.

Serum KL-6 levels in lung cancer patients with or without interstitial lung disease

BACKGROUND

It is not known whether lung cancer patients with interstitial lung disease (ILD) might have higher serum levels of KL-6, a high molecular weight glycoprotein classified as a polymorphic epithelial mucin. In addition, prognosis of these patients with elevated serum KL-6 levels might be poorer than that with normal KL-6 levels, but it has not been well clarified.

METHODS

Serum KL-6 levels in 273 lung cancer patients with or without ILD, and prognostic significance of elevated serum KL-6 levels in these patients were studied using uni- and multivariate analyses.

RESULTS

Serum KL-6 levels were elevated (>500 U/ml) in 73.5% of lung cancer patients with ILD and in 33.7% of those without ILD. Serum KL-6 levels in lung cancer patients with ILD were significantly higher than those without ILD. In lung cancer patients with ILD, elevated serum KL-6 has no prognostic significance, but in those without ILD, however, it was one of the unfavorable prognostic factors.

CONCLUSIONS

Elevated serum KL-6 levels can be observed in lung cancer patients both with and without ILD. Having ILD has strong prognostic impact in patients with lung cancer. In those without ILD, however, elevated KL-6 levels may be related to poor prognosis.

Clinical and radiological features of acute-onset diffuse interstitial lung diseases in patients with rheumatoid arthritis receiving treatment with biological agents: importance of Pneumocystis pneumonia in Japan revealed by a multicenter study

OBJECTIVE

Acute-onset diffuse interstitial lung disease (AoDILD) in patients with rheumatoid arthritis (RA) has been a serious concern, especially for those under treatment with biological agents which may affect the presentation and outcome of AoDILD, including Pneumocystis pneumonia (PCP). Therefore, we conducted a retrospective, multi-center study of AoDILD in RA patients receiving biological agents.

METHODS

Patients who developed AoDILD while receiving biological agents (infliximab, etanercept, adalimumab and tocilizumab) were enrolled in the study. Definite PCP was defined as patients who showed either P. jirovecii organisms in their respiratory samples by microscopic examination, or positive tests for both P. jirovicii DNA-PCR with respiratory samples and an elevated serum 1,3-β-D-glucan level above the cut-off value. Probable PCP was defined as either a positive test for P. jirovicii PCR or an elevated serum β-D-glucan level. Chest HRCT findings were evaluated and scored by two board-certified radiologists.

RESULTS

The final diagnoses for 26 patients examined were definite PCP for 13 patients, probable PCP for 11, and methotrexate-associated pneumonitis in 2 patients. Definite and probable PCP cases were clinically indistinguishable. Generalized, diffuse ground-glass opacity (GGO) is the characteristic HRCT finding in patients with definite or probable PCP, which was different from our previous findings in RA patients, mostly without biologics, showing GGO distributed in a panlobular or multilobular manner. The clinical outcome was favorable by treatment with trimethoprim-sulfamethoxazole and glucocorticoids.

CONCLUSION

The possibility of PCP should be intensively investigated in RA patients developing AoDILD while receiving biological agents.

Serum KL-6 level as an indicator of active or inactive interstitial pneumonitis associated with connective tissue diseases

OBJECTIVE

To elucidate the cut off levels of serum KL-6 indicating patients with interstitial pneumonitis (IP) and patients with active IP associated with connective tissue diseases (CTDs).

METHODS

CTD patients whose serum KL-6 level was measured were included. IP was diagnosed on the basis of medical records including XP/CT findings, and active IP was assumed in case that intervention for IP was newly added. The cut off levels were determined by receiver operating characteristic (ROC) curve analysis.

RESULTS

Among 240 (174 females) patients, 67 (42) had IP and 15 (9) had active IP. The ages of patients with and without IP, and with active IP and with inactive IP were 70.3±9.5 and 62.8±15.3, and 72.8±8.1 and 69.6±9.8, respectively. IP was significantly more prevalent in males and the elderly. The KL-6 levels were 990±90 and 301±12 U/mL in patients with and without IP, and 1,905±236 and 726±54 U/mL in those with active IP and with inactive IP, respectively. ROC curve analysis showed a cut off level of 509 U/mL for indicating IP, and that of 1,051-1,060 U/mL for indicating active IP.

CONCLUSION

A serum KL-6 level of higher than 500 U/mL is a marker of the presence of IP, and a level of higher than 1,000 U/mL is a marker of the presence of active IP associated with CTDs.

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.

Increased levels of KL-6 and subsequent mortality in patients with interstitial lung diseases

OBJECTIVES

KL-6 is a specific marker in patients with interstitial lung diseases (ILDs); however, the relationship between elevated levels of KL-6 and subsequent mortality is not well defined. To determine if elevated serum levels of KL-6 are associated with increased mortality, and to identify the most suitable cut-off level of KL-6 by which to distinguish between good prognosis and poor prognosis, we evaluated the prognostic significance of serum KL-6 levels in patients with stable-state ILDs.

METHODS

Two hundred and nineteen patients diagnosed with ILDs (152 with idiopathic interstitial pneumonia and 67 with collagen disease-associated pulmonary fibrosis) at Tsukuba University Hospital from April 1999 to October 2005 were entered in this study. Serum KL-6 levels in patients with ILDs were measured with a commercially available enzyme immunoassay kit, and these patients were then followed up.

RESULTS

During the follow-up period, 58 of the 219 patients died of respiratory failure. Patients who died during this period had higher levels of KL-6 than did those who did not (P = 0.0004). The receiver operating characteristic curve analysis showed 1000 U mL(-1) as the most suitable cut-off level by which to distinguish between the two groups of patients. The 95% specificity serum KL-6 level with poor outcome was 2750 U mL(-1). In univariate and multivariate analysis, elevated serum KL-6 (>1000 U mL(-1)) in the stable state indicated poor prognosis (P = 0.0005, log-rank test; P = 0.0001, Cox proportional hazard model).

CONCLUSIONS

Elevated KL-6 level may provide simple, yet valuable information by which to identify patients with ILDs who are at increased risk for subsequent mortality.

Serum KL-6 and Surfactant Proteins A and D in Pediatric Interstitial Lung Disease

OBJECTIVE

To determine if serum KL-6, surfactant protein A (SP-A), and surfactant protein D (SP-D) levels are elevated in pediatric interstitial lung disease (ILD) and associated with pulmonary function and disease severity score.

METHODS

Serum KL-6, SP-A, and SP-D levels were measured by enzyme-linked immunosorbent assay in 10 children with ILD and in 10 healthy volunteers. In the ILD group, FEV1 percentage of predicted, FVC percentage of predicted, and ILD disease severity score were measured and correlated with serum KL-6, SP-A, and SP-D levels.

RESULTS

For the ILD and control groups, respectively, mean serum KL-6 was 4,523 U/mL and 206 U/mL (p = 0.007), mean serum SP-A was 133 ng/mL and 21 ng/mL (p = 0.003), and mean serum SP-D was 304 ng/mL and 75 ng/mL (p = 0.004). There was an inverse relationship between SP-A and FVC (p = 0.05), and between SP-D and FEV1 (p = 0.05). There was a direct relationship between SP-D and ILD score (p = 0.05).

CONCLUSIONS

Serum KL-6, SP-D and SP-D levels are elevated in children with ILD. SP-A and SP-D levels appear to correlate with some measures of disease severity.

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

OBJECTIVE

To determine the role of KL-6 (Krebs von den Lungen-6) in evaluating the disease severity of pulmonary lesions in rheumatoid arthritis (RA) compared with high resolution computed tomography (HRCT) findings.

METHODS

Fifty serum KL-6 levels and HRCT images were prospectively obtained from 47 RA patients. Eight HRCT findings were classified into five grades. Patients were also divided into two groups according to the KL-6 threshold level and HRCT findings were evaluated.

RESULTS

There was a positive correlation between the serum KL-6 level and the total CT score (r = 0.83). Reticular opacity most closely related to the serum KL-6 levels (r = 0.84). In the high KL-6 group (n = 10), the average CTscore was markedly increased (64.6 points) and severe honeycombing expanded into the whole lung. One case revealed diffuse ground glass opacity. In 12 of 40 cases in the normal KL-6 group, CT scores mildly increased compared with the other cases (over 20 points). The predominant finding of these cases could be classified into four types: (1) narrow spread honeycombing; (2) subtle fibrosis; (3) airway diseases; and (4) dense consolidation.

CONCLUSION

KL-6 is a useful marker to detect severe RA lung disease. It is also useful to distinguish non-fibrosis from fibrosis predominant cases. However, it sometimes could not detect early stage RA lung disease.

Diagnostic accuracy of KL-6 as a marker of amiodarone-induced pulmonary toxicity

The diagnostic accuracy of KL-6 as an indicator of amiodarone-induced pulmonary toxicity was studied in 14 men (mean age = 62 +/- 12, range 33-76 years) treated with amiodarone. The indications for amiodarone were sustained ventricular tachycardia in 13 patients and atrial fibrillation in 1 patient with refractory heart failure. The KL-6 cut-off level was set at 520 U/mL. Group A consisted of two patients with amiodarone-induced pulmonary toxicity, group B of five patients with other pulmonary disorders, and group C of seven patients without pulmonary disease. KL-6 levels, percent diffusing capacity for carbon monoxide (%DLCO), and other laboratory markers were compared among these three groups. KL-6 levels were significantly higher in group A than in group B and C (2550 +/- 36, 252 +/- 99, 198 +/- 82 U/mL, respectively; P < 0.0001). KL-6 levels in group B were below the cutoff value. %DLCO, C-reactive protein (CRP), and lactic dehydrogenase (LDH) were abnormal in group A. The abnormal rates of CRP and LDH in group B were 80% and 40%, respectively. Of the seven patients with pulmonary disease, three patients (43%) could not undergo %DLCO testing because of poor physical condition. In one patient with amiodarone-induced pulmonary toxicity, the KL-6 level increased from 695 to 2,100 U/mL at a time of progression of interstitial changes. KL-6 may be a useful marker of amiodarone-induced pulmonary toxicity.

Circulating KL-6 predicts the outcome of rapidly progressive idiopathic pulmonary fibrosis

Searching for early predictive markers of the therapeutic effects of high-dose corticosteroids ("pulse therapy") on patients with rapidly progressing idiopathic pulmonary fibrosis (IPF), we evaluated 14 such patients, who had received weekly pulse therapy for at least 3 wk. Eight patients responded to the treatment and survived. However, six patients failed to respond, and all of them died within 3 mo after treatment. Serum levels of KL-6 (MUC1 mucin), neutrophil elastase (NE), and lactate dehydrogenase (LDH) were measured before, and at 1 wk and 3 wk after treatment. Levels of KL-6 decreased significantly in patients who lived, whereas KL-6 levels tended to increase in patients who died. The values of NE did not change significantly. LDH levels decreased significantly at 1 wk, and tended to decrease at 3 wk in patients who lived. However, in patients who died, they did not significantly change. At the first cycle of treatment when clinical effects may not be evident, the decrease in KL-6 but not LDH levels was significantly related to a favorable outcome, whereas their increase was related to a poor outcome. Results suggest that monitoring with KL-6 may contribute to early clinical decisions for alternative therapy in the management of rapidly progressing IPF.