Elevated serum KL-6 levels in patients with systemic sclerosis: association with the severity of pulmonary fibrosis

Targeting Progression in Pulmonary Fibrosis: An Overview of Underlying Mechanisms, Molecular Biomarkers, and Therapeutic Intervention

Interstitial lung diseases comprise a heterogenous range of diffuse lung disorders, potentially resulting in pulmonary fibrosis. While idiopathic pulmonary fibrosis has been recognized as the paradigm of a progressive fibrosing interstitial lung disease, other conditions with a progressive fibrosing phenotype characterized by a significant deterioration of the lung function may lead to a burden of significant symptoms, a reduced quality of life, and increased mortality, despite treatment. There is now evidence indicating that some common underlying biological mechanisms can be shared among different chronic fibrosing disorders; therefore, different biomarkers for disease-activity monitoring and prognostic assessment are under evaluation. Thus, understanding the common pathways that induce the progression of pulmonary fibrosis, comprehending the diversity of these diseases, and identifying new molecular markers and potential therapeutic targets remain highly crucial assignments. The purpose of this review is to examine the main pathological mechanisms regulating the progression of fibrosis in interstitial lung diseases and to provide an overview of potential biomarker and therapeutic options for patients with progressive pulmonary fibrosis.

Association of elevated serum carbohydrate antigen 19-9 levels with extensive interstitial lung disease in patients with systemic sclerosis: A cross-sectional study

AIM

To assess the usefulness of carbohydrate antigen 19-9 (CA19-9) as a biomarker for systemic sclerosis-associated interstitial lung disease (SSc-ILD), using serum samples and clinical parameters of patients with SSc.

METHODS

Patients with SSc admitted to Tokyo Women's Medical University Hospital between 2010 and 2021 and those who underwent chest computed tomography (CT) were included. Patients were diagnosed with ILD based on chest CT findings, and SSc-ILD was categorized as either a limited or extensive disease based on chest CT and pulmonary function test findings. Serum CA19-9 levels were measured in 56 patients with SSc and in 32 healthy individuals. Additionally, we evaluated the difference in serum CA19-9 levels between the groups, the correlation with ILD area and pulmonary function, and discriminative performance to diagnose extensive ILD.

RESULTS

Of the 56 patients with SSc, 40 (71.4%) had ILD, and 17 (30.4%) were classified as having extensive disease. Serum CA19-9 levels were significantly elevated in patients with extensive disease compared to those with limited disease (median [interquartile range]: 25.7 U/mL [10.1-50.8] vs. 8.8 U/mL [4.5-17.6], p = .02) and correlated with ILD area (r = .30, p = .02). There was no significant correlation between serum CA19-9 level and pulmonary function. The cutoff of CA19-9 for the diagnosis of the extensive disease was determined to be 19.8 U/mL, with a sensitivity of 64% and specificity of 82% and an area under the curve of 0.74 (95% confidence interval 0.58-0.90).

CONCLUSION

The serum CA19-9 level may be a useful marker for identifying patients with SSc-ILD with extensive disease.

Long-term Outcomes After Rituximab Treatment for Patients With Systemic Sclerosis: Follow-up of the DESIRES Trial With a Focus on Serum Immunoglobulin Levels

Importance

Rituximab is emerging as a promising therapeutic option for systemic sclerosis (SSc), but its long-term outcomes and response markers are unknown.

Objective

To evaluate the long-term outcomes after rituximab treatment for SSc and identify potential response markers.

Design, Setting, and Participants

In this single-center cohort study, patients with SSc who continued to receive rituximab after the DESIRES trial were analyzed with a median follow-up of 96 weeks. Among the 43 patients who completed the DESIRES trial, 31 continued to receive rituximab, of which 29 with complete data were included in this study.

Exposures

Rituximab treatment.

Main Outcomes and Measures

A post hoc analysis of the clinical and laboratory data.

Results

In 29 patients with SSc (27 female [93%]; median [IQR] age, 48 [35-45] years), significant improvement in modified Rodnan skin score (MRSS) and percentage of predicted forced vital capacity (FVC%) were observed after 1 (median [IQR] change in MRSS, -7 [-8.5 to -4]; P < .001) and 3 (median [IQR] change in FVC% predicted, 1.85 [0.13-5.68]; P < .001) courses of rituximab, respectively, both of which were sustained during follow-up. High responders (MRSS improvement of ≥9; n = 16) experienced a greater decrease in serum levels of IgG (median [IQR] change in IgG, -125 [-207 to -83] vs 7 [-120 to 43]; P = .008) and IgA (median [IQR] change in IgA, -45 [-96 to -32] vs -11 [-20 to 3]; P < .001) compared with low responders (MRSS improvement of ≤8; n = 13). In particular, decrease in serum IgA levels significantly correlated with the improvement in MRSS (r = 0.64; P < .001). At the last follow-up, low IgM, low IgA, and low IgG was observed in 7, 1, and 1 patient, respectively, of which low IgM was associated with greater improvement in FVC% predicted (median [IQR] change in FVC% predicted, 7.2 [3.8-8.9] vs 3.6 [1.4-6.2]; P = .003).

Conclusions and Relevance

In this cohort study, rituximab treatment was associated with significantly improved skin and lung fibrosis in SSc in a long-term follow-up. Decrease in serum immunoglobulins was associated with greater clinical response.

Serum KL-6 as a Biomarker of Progression at Any Time in Fibrotic Interstitial Lung Disease

The development of a progressive phenotype of interstitial lung disease (ILD) is still unpredictable. Whereas tools to predict mortality in ILD exist, scores to predict disease progression are missing. The aim of this study was to investigate whether baseline serum KL-6 as an established marker to assess disease activity in ILD, alone or in combination with clinical variables, could improve stratification of ILD patients according to progression risk at any time. Consecutive patients with fibrotic ILD, followed at our institution between 2008 and 2015, were investigated. Disease progression was defined as relative decline of ≥10% in forced vital capacity (FVC) or ≥15% in diffusing capacity of the lung for carbon monoxide (DLco)% from baseline at any time. Serum KL-6 was measured using an automated immunoassay (Fujirebio Europe, Gent, Belgium). A stepwise logistic regression was performed to select variables to be included in the score. A total of 205 patients (49% idiopathic pulmonary fibrosis (IPF), 51% fibrotic nonspecific interstitial pneumonia (NSIP)) were included, of them 113 (55%) developed disease progression during follow up. Male gender (G) and serum KL-6 strata (K) were significant predictors of progression at regression analysis and were included in the GK score. A threshold of 2 GK score points was best for discriminating patients at high risk versus low risk to develop disease progression at any time. Serum KL-6 concentration, alone or combined in a simple score with gender, allows an effective stratification of ILD patients for risk of disease progression at any time.

Comparing clinical characteristics of systemic sclerosis with or without interstitial lung disease: A cross-sectional study from a single center of the Chinese Rheumatism Data Center

Background

We aimed to compare the clinical characteristics of patients with systemic sclerosis (SSc) with or without interstitial lung disease (ILD) to identify relationships with the presence of ILD in SSc at a single center in China.

Methods

A cross-sectional study was conducted using retrospective data from the Chinese Rheumatology Data Center. Patients diagnosed with SSc at the Second Affiliated Hospital of Nanchang University between 2013 and 2022 were included. Demographic and clinical characteristics were compared between patients with SSc with and without ILD. Logistic regression analyses were performed to explore these associations.

Results

A total of 227 patients with SSc were included (male:female ratio = 1:4.82), of which 121 (53.3%) were accompanied with ILD. SSc patients with ILD had a higher percentage of diffuse cutaneous systemic sclerosis (dcSSc), sclerodactyly, loss of finger pad, muscle involvement, left ventricular diastolic dysfunction (LVDD), and pulmonary hypertension (PAH), elevated Krebs von den Lungen-6 (KL-6), and elevated ferritin than those without ILD, and a higher modified Rodnan skin score (mRSS), neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) (all P < 0.05). Antinuclear antibody (ANA) and anti-scleroderma-70 (anti-Scl-70) positivity was presented frequently in SSc patients with ILD, while SSc patients without ILD were more often anti-centromere antibody (ACA) positive (all P < 0.05). On the multivariable analysis, muscle involvement [OR 2.551 (95% CI 1.054-6.175), P = 0.038], LVDD [OR 2.360 (95% CI 1.277-4.361), P = 0.006], PAH [OR 9.134 (95% CI 2.335-35.730), P = 0.001], dcSSc [OR 2.859 (95% CI 1.489-5.487), P = 0.002], PLR [OR 1.005 (95% CI 1.001-1.008), P = 0.020], elevated KL-6 [OR 2.033 (95% CI 1.099-3.763), P = 0.024], and anti-Scl-70 [OR 3.101 (95% CI 1.647-5.840), P < 0.001] were statistically significant associations with SSc patients with ILD.

Conclusion

Systemic sclerosis was found mainly in females. Several important differences in clinical and laboratory characteristics have been demonstrated between SSc patients with or without ILD. Muscle involvement, LVDD, PAH, dcSSc, PLR, elevated KL-6, and Anti-Scl-70 antibody may be associated with SSc in patients with ILD.

Krebs von den Lungen-6 levels in untreated idiopathic pulmonary fibrosis

Background

Serum Krebs von den Lungen‐6 (KL‐6) has been reported to be elevated in patients with idiopathic pulmonary fibrosis (IPF).

Objective

The aim of this study was to evaluate the diagnostic value of KL‐6 and whether the expression value of KL‐6 could indicate the severity of the disease in IPF patients. To address this question, it is necessary to see whether the patients' physical characteristics and other clinical conditions could affect the baseline KL‐6 level.

Design

We conducted a study of 100 patients who were diagnosed with IPF. Lung function, computed tomography (CT), and serological lab tests data were analyzed.

Results

The tests showed that there is a significant elevation of KL‐6 in IPF patients compared with other interstitial lung disease (ILD) and healthy controls. It was noted that serum KL‐6 is a stable biomarker not affected by lung infection and smoking, though IPF patients with antinuclear antibody (ANA) showed higher KL‐6 levels. KL‐6, in conjunction with poor pulmonary function and higher radiological fibrosis scores, indicates the severity of the disease but not poor survival.

Conclusions

It is identified that serum KL‐6 is a useful noninvasive biomarker to help improve the certainty of IPF diagnosis from other interstitial lung disease and assist evaluation of disease severity and prognosis.

Prevalence and risk factors of systemic sclerosis-associated interstitial lung disease in East Asia: A systematic review and meta-analysis

Objective

Interstitial lung disease (ILD) is a common and potentially life‐threatening complication for individuals with systemic sclerosis (SSc). The purpose of this study was to complete a systematic review and meta‐analysis on prevalence and risk factors of SSc‐ILD in East Asia.

Methods

Medline, EMBASE, and Cochrane Library were searched up to January 22, 2021. The Reporting of Observational Studies in Epidemiology (STROBE) statement was applied to access the methodological quality of the eligible studies. Study characteristics and magnitude of effect sizes were extracted. Then, we calculated the pooled prevalence, weighted mean differences (WMDs), pooled odds ratios (ORs) with corresponding 95% confidence intervals (CIs), and performed subgroup analysis, sensitivity analysis, and publication bias with Egger's test.

Results

Twenty‐seven of 1584 articles were eligible and a total of 5250 patients with SSc were selected in the meta‐analysis. The pooled prevalence of SSc‐ILD in East Asia was 56% (95% CI 49%‐63%). The SSc‐ILD prevalence was higher in China (72%) than in Japan (46%) and Korea (51%). Longer disease duration (WMD = 1.97, 95% CI 0.55‐3.38), diffuse SSc (OR = 2.84, 95% CI 1.91‐4.21), positive anti‐topoisomerase I antibody (ATA) (OR = 4.92, 95% CI 2.74‐8.84), positive anti‐centromere body antibody (ACA) (OR = 0.14, 95% CI 0.08‐0.25), positive anti‐U3 ribonucleoprotein (RNP) antibody (OR = 0.17, 95% CI 0.04‐0.66), and higher erythrocyte sedimentation rate (ESR) (WMD = 6.62, 95% CI 1.19‐12.05) were associated with SSc‐ILD in East Asia.

Conclusion

Through this systematic review and meta‐analysis, we found that ILD occurs in up to approximately 56% of patients with SSc in East Asia. Longer disease duration, diffuse SSc, positive ATA, negative ACA, negative anti‐U3 RNP antibody, and higher ESR were risk factors for SSc‐ILD.

Biomarkers in Progressive Fibrosing Interstitial Lung Disease: Optimizing Diagnosis, Prognosis, and Treatment Response

Interstitial lung disease (ILD) comprises a heterogenous group of diffuse lung disorders that commonly result in irreversible pulmonary fibrosis. While idiopathic pulmonary fibrosis (IPF) is the prototypical progressive fibrosing ILD (PF-ILD), a high proportion of patients with other ILD subtypes develop a PF-ILD phenotype. Evidence exists for shared pathobiology leading to progressive fibrosis, suggesting that biomarkers of disease activity may prove informative across the wide spectrum of ILDs. Biomarker investigation to date has identified a number of molecular markers that predict relevant ILD endpoints, including disease presence, prognosis, and/or treatment response. In this review, we provide an overview of potentially informative biomarkers in patients with ILD, including those suggestive of a PF-ILD phenotype. We highlight the recent genomic, transcriptomic, and proteomic investigations that identified these biomarkers and discuss the body compartments in which they are found, including the peripheral blood, airway, and lung parenchyma. Finally, we identify critical gaps in knowledge within the field of ILD biomarker research and propose steps to advance the field toward biomarker implementation.

Serum TARC Levels in Patients with Systemic Sclerosis: Clinical Association with Interstitial Lung Disease

Systemic sclerosis (SSc) is a multisystem fibrotic disorder with autoimmune background. Accumulating evidence has highlighted the importance of T helper (Th) 2 cells in the pathogenesis of SSc and its complications. Because thymus and activation-regulated chemokine (TARC) is a potent chemoattractant for Th2 cells, we measured serum TARC levels in SSc patients and analyzed their correlation with interstitial lung disease (ILD), a major complication of SSc. Serum TARC levels were significantly elevated in patients with SSc, especially in those with the diffuse subtype, compared with healthy controls. In particular, dcSSc patients with SSc-associated ILD (SSc-ILD) showed higher TARC levels than those without SSc-ILD. However, there was no significant correlation between serum TARC levels and pulmonary function in SSc patients. Serum TARC levels did not correlate with serum levels of interleukin-13, an important Th2 cytokine, either. Furthermore, in the longitudinal study, serum TARC levels did not predict the onset or progression of SSc-ILD in patients with SSc. These results were in contrast with those of KL-6 and surfactant protein D, which correlated well with the onset, severity, and progression of SSc-ILD. Overall, these results suggest that serum TARC levels are not suitable for monitoring the disease activity of SSc-ILD.

Serum markers of pulmonary epithelial damage in systemic sclerosis-associated interstitial lung disease and disease progression

BACKGROUND AND OBJECTIVE

The course of systemic sclerosis-associated interstitial lung disease (SSc-ILD) is highly variable, and accurate prognostic markers are needed. KL-6 is a mucin-like glycoprotein (MUC1) expressed by type II pneumocytes, while CYFRA 21-1 is expressed by alveolar and bronchiolar epithelial cells. Both are released into the blood from cell injury.

METHODS

Serum KL-6 and CYFRA 21-1 levels were measured in a retrospective (n = 189) and a prospective (n = 118) cohort of SSc patients. Genotyping of MUC1 rs4072037 was performed. Linear mixed-effect models were used to evaluate the relationship with change in lung function parameters over time, while association with survival was evaluated with Cox proportional hazard analysis.

RESULTS

In both cohorts, KL-6 and CYFRA 21-1 were highest in patients with lung involvement, and in patients with extensive rather than limited ILD. KL-6 was higher in patients carrying the MUC1 rs4072037 G allele in both cohorts. In patients with SSc-ILD, serum KL-6, but not CYFRA 21-1, was significantly associated with DL_CO decline in both cohorts (P = 0.001 and P = 0.004, respectively), and with FVC decline in the retrospective cohort (P = 0.005), but not the prospective cohort. When combining the cohorts and subgrouping by severity (median CPI = 45.97), KL-6 remained predictive of decline in DL_CO in both milder (P = 0.007) and more severe disease (P = 0.02) on multivariable analysis correcting for age, gender, ethnicity, smoking history and MUC1 allele carriage.

CONCLUSION

Our results suggest serum KL-6 predicts decline in lung function in SSc, suggesting its clinical utility in risk stratification for progressive SSc-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.

Biomarkers in systemic sclerosis-associated interstitial lung disease: review of the literature

SSc is a rare disease of unknown origin associated with multiple organ involvement. One of the major complications that drives the mortality of SSc patients is interstitial lung disease. The course of SSc-interstitial lung disease progression has a wide spectrum. Since the treatment is based on aggressive immunosuppression it should not be given to stable or non-progressing disease. The correct identification of disease with high risk of progression remains a challenge for early therapeutic intervention, and biomarkers remain urgently needed. In fact, eight categories of biomarkers have been identified and classified according to the different biological pathways involved. The purpose of this article is to describe the main biomarkers thought to be of interest with clinical value in the diagnosis and prognosis of SSc-interstitial lung disease.

Serum levels of Krebs von den Lungen-6 as a promising marker for predicting occurrence and deterioration of systemic sclerosis-associated interstitial lung disease from a Chinese cohort

AIM

A prospective and longitudinal study to investigate the correlations between Krebs von den Lungen-6 (KL-6) serum levels and systemic sclerosis associated with interstitial lung disease (SSc-ILD).

METHOD

Blood samples of baseline and the time point at 2 years follow-up intervals were collected for the measurement of serum KL-6 levels. The baseline clinical, laboratory characteristics, and incidence density of newly diagnosed ILD during the follow up were compared between SSc patients with elevated serum KL-6 levels (KL-6 > 500 U/mL) and those with normal KL-6 levels (KL-6 ≤ 500 U/mL) at baseline. Further, we explored the association between serum KL-6 and deterioration of ILD measured by lung function parameters during follow-up of 2 years.

RESULTS

Patients with elevated baseline serum KL-6 had a significant tendency to have disappearance of the finger pad. The incidence density of new-onset ILD in SSc patients with elevated baseline serum KL-6 and those with normal baseline serum KL-6 was 1.33% and 0.51%, respectively. Among the mild lung injury group, the incidence density of ILD deterioration in SSc patients with elevated baseline serum KL-6 and those with normal serum KL-6 was 1.2% and 0.74%, respectively.

CONCLUSION

Serum KL-6 level correlates with the clinical manifestations of microvascular injury. Baseline elevated serum KL-6 may predict deterioration of lung function of SSc-ILD patients with mild lung injury.

KL-6 But Not CCL-18 Is a Predictor of Early Progression in Systemic Sclerosis-related Interstitial Lung Disease

OBJECTIVE

The 2 pneumoproteins, KL-6 and CCL-18, are promising biomarkers in systemic sclerosis (SSc)-related interstitial lung disease (ILD). Our goal was to determine their predictive significance for forced vital capacity % (FVC%) decline within the first year of followup in patients with early SSc-ILD.

METHODS

Early SSc patients with imaging-verified ILD enrolled in the Genetics versus Environment in Scleroderma Outcome Study (GENISOS) cohort were included. Annualized rate of change in FVC% based on the baseline and followup measurement within 12-18 months was used as the surrogate outcomes for ILD progression.

RESULTS

Eighty-two early SSc-ILD patients with mean disease duration of 2.3 years were investigated. FVC% change ranged from -23% to 38%. Baseline KL-6 levels were higher in patients than healthy controls (p < 0.0001). Higher KL-6 levels were predictive of faster FVC% decline at the 1-year followup (r = -0.23, p = 0.037). Upon categorizing KL-6 using a previously published cutoff of 1273 U/ml, its predictive significance remained in the univariable model (b = -0.07, p = 0.01), indicating that patients with positive KL-6 had on average 7% more decline in annualized percent change of FVC%. Moreover, KL-6 remained an independent predictor after adjustment for sex, disease type, anti-Scl-70, and immunosuppressive treatment status in multivariable models. Although CCL-18 was higher in patients than controls (p < 0.001), its levels did not predict FVC decline rate (p = 0.458).

CONCLUSION

KL-6 but not CCL-18 is predictive of early SSc-ILD progression. KL-6 is a promising pneumoprotein that can contribute to SSc-ILD clinical trial enrichment.

Elevated serum Krebs von den Lungen-6 in systemic sclerosis: a marker of lung fibrosis and severity of the disease

OBJECTIVES

We aimed to assess the clinical significance of Krebs von den Lungen-6 (KL-6) in the diagnosis and severity of interstitial lung disease (ILD) in a French cohort of patients with systemic sclerosis (SSc).

METHODS

Serum KL-6 concentrations were measured with chemiluminescent enzyme immunoassay (CLEIA) in 75 SSc patients. Patients were divided into two groups according to the presence of interstitial lung disease (SSc-ILD versus SSc-without ILD) on chest High-Resolution Computed Tomography. Pulmonary function tests, main manifestations and severity of the lung disease (Medsger's severity scale) were collected.

RESULTS

KL-6 serum concentrations were significantly higher in SSc-ILD patients than in those without ILD (p < 10^-4) and were inversely correlated with forced vital capacity, total lung capacity and diffuse lung capacity of carbon monoxide. Serum KL-6 level superior to 872 U/ml appeared as the optimal cut-off value associated with ILD. Patients with a restrictive pulmonary syndrome and dyspnoea had significant higher KL-6 serum concentrations. SSc patients with anti-topoisomerase 1 antibodies had higher KL-6 serum levels than patients with anti-centromere antibodies (p < 10^- 4). ILD and anti-topoisomerase 1 antibodies were independent factors associated with KL-6 in multivariate analysis. Interestingly, KL-6 serum concentrations positively increased with the patient lung severity.

CONCLUSIONS

Our study confirms that KL-6 is an accurate biomarker for the diagnosis of SSc-ILD in a French cohort of patients. High KL-6 levels should prompt physicians to assess ILD with pulmonary imaging and pulmonary functions tests. Prospective clinical studies are still required to determine whether levels of KL-6 might predict progression of ILD as well as its usefulness in the timing of therapeutic intervention.

Elevated Serum Krebs von den Lungen-6 in Early Disease Predicts Subsequent Deterioration of Pulmonary Function in Patients with Systemic Sclerosis and Interstitial Lung Disease

Objective.

To identify predictors of poor prognosis in patients with systemic sclerosis (SSc) associated with interstitial lung disease (ILD).

Methods.

Fifty patients with early-stage SSc-ILD who had never received disease-modifying drugs and were either observed for ≥ 10 years or died from ILD-related causes were enrolled. The baseline variables of patients who developed endstage lung disease (ESLD) were compared with those of patients who remained ESLD-free, and the Cox proportional hazard model was used to identify initial factors that correlated with ESLD development.

Results.

Sixteen patients (32%) developed ESLD during 173.5 ± 64.7 months of followup. Elevated serum Krebs von den Lungen-6 (KL-6) at initial assessment was highly correlated with ESLD development (p = 0.0002). Receiver-operating characteristic curve analysis revealed that a KL-6 value of 1273 U/ml effectively discriminated patients who developed ESLD from those who did not. Patients with KL-6 > 1273 U/ml were less likely to remain ESLD-free compared with those with lower KL-6 levels (p < 0.0001). Multivariate analysis showed that KL-6 > 1273 U/ml was the most reliable predictor of ESLD development (OR 51.2, 95% CI 7.6–343, p < 0.0001). Finally, the initial KL-6 level correlated with the forced vital capacity (FVC) decline rate (r = 0.58, p < 0.0001).

Conclusion.

The natural course of SSc-ILD is highly variable. Baseline serum KL-6 is a biomarker potentially useful for predicting FVC decline.

Risk factors for severity and manifestations in systemic sclerosis and prediction of disease course

Systemic sclerosis (SSc, or scleroderma) is a rheumatic disease with distinct features that encompass autoimmunity, vascular lesions (vasculopathy) and tissue fibrosis. The disease has a high morbidity and mortality compared with other rheumatic diseases. This review discusses risk factors and markers that predict the disease course and the occurrence of disease manifestations, with an emphasis on major organ involvement. In addition, risk factors will be described that are associated with mortality in SSc patients. The review addresses the impact of recent developments on screening, diagnosis and risk stratification as well as the need for further research where data are lacking.

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.

Involvement of CD161+ Vδ1+ γδ T cells in systemic sclerosis: association with interstitial pneumonia

OBJECTIVE

Interstitial pneumonia (IP) is a chronic progressive interstitial lung disease associated with high mortality and poor prognosis. However, the pathogenesis of IP remains to be elucidated. The aim of this study was to clarify the role of CD161(+) Vδ1(+) γδ T cells in SSc patients with IP.

METHODS

The proportion of CD161(+) Vδ1(+) γδ T cells in peripheral blood mononuclear cells (PBMCs) and serum sialylated carbohydrate antigen (KL-6) levels were determined. GeneChip analysis was performed with CD161(-) and CD161(+) Vδ1(+) γδ T cells. Cytokine and chemokine expression from CD161(+) Vδ1(+) γδ T cells was measured and used to evaluate the effect of culture supernatant on fibroblast proliferation.

RESULTS

The proportion of CD161(+) Vδ1(+) γδ T cells was significantly higher in SSc than healthy controls (HCs) and correlated negatively with serum KL-6 levels in IP-positive SSc patients. The gene and mRNA expression level of chemokine ligand 3 (CCL3) was markedly higher in CD161(+) Vδ1(+) γδ T cells than in CD161(-) Vδ1(+) γδ T cells. CD161(+) Vδ1(+) γδ T cells in IP-positive SSc patients showed higher production of CCL3 and lower production of IFN-γ than in HCs. Culture supernatant derived from IP-negative and IP-positive SSc patients promoted fibroblast proliferation, whereas that from HCs did not.

CONCLUSION

The small proportion and the altered cell functions of CD161(+) Vδ1(+) γδ T cells among PBMCs in SSc patients play a role in the pathogenesis of IP. These findings suggest that CD161(+) Vδ1(+) γδ T cells may play a regulatory role in the pathogenesis of IP in SSc patients via IFN-γ production.

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.

Serum Interleukin 6 Is Predictive of Early Functional Decline and Mortality in Interstitial Lung Disease Associated with Systemic Sclerosis

Objective.

Biomarkers of progression of interstitial lung disease (ILD) are needed to allow early therapeutic intervention in patients with scleroderma-associated disease (SSc-ILD).

Methods.

A panel of 8 serum cytokines [interleukin 6 (IL-6), IL-8, IL-10, CCL2, CXCL10, vascular endothelial growth factor, fibroblast growth factor 2, and CX3CL1] was assessed by Luminex bead technology in exploratory cohorts of 74 patients with SSc and 58 patients with idiopathic pulmonary fibrosis (IPF). Mortality and significant lung function decline [forced vital capacity (FVC) ≥ 10%; DLCO ≥ 15%] from date of serum collection were evaluated by proportional hazards analysis. Based on these findings, the prognostic value of serum IL-6, evaluated by ELISA, was assessed in a larger test cohort of 212 patients with SSc-ILD.

Results.

In the exploratory cohort, only serum IL-6 was an independent predictor of DLCO decline in both IPF and SSc-ILD. The IL-6 threshold level most predictive of DLCO decline within a year was 7.67 pg/ml. In the larger test cohort, serum IL-6 > 7.67 pg/ml was predictive of decline in FVC (HR 2.58 ± 0.98, p = 0.01) and in DLCO (HR 3.2 ± 1.7, p = 0.02) within the first year, and predictive of death within the first 30 months (HR 2.69 ± 0.96, p = 0.005). When stratified according to severity (FVC < 70%), serum IL-6 > 7.67 pg/ml was predictive of functional decline or death within the first year in patients with milder disease (OR 3.1, 95% CI 1.4–7.2, p = 0.007), but not in those with severe ILD.

Conclusion.

In SSc-ILD, serum IL-6 levels appear to be predictive of early disease progression in patients with mild ILD, and could be used to target treatment in this group, if confirmed by prospective studies.

Biomarkers in systemic sclerosis

Systemic sclerosis is an autoimmune inflammatory disorder of unknown etiologycharacterized b y pronounced fibroproliferative alterations in the microvasculature, and frequent cellular and humoral immunity abnormalities, culminating in a severe and often progressive fibrotic process. Numerous biomarkers reflecting the three main pathogenetic mechanisms in systemic sclerosis have been described; however, aside from several disease-specific autoantibodies, other biomarkers have not been thoroughly validated and require further study. Thus, there is an unmet need for validated biomarkers for diagnosis, disease classification, and evaluation of organ involvement and therapeutic response in systemic sclerosis.

Elevated serum concentrations of polymorphonuclear neutrophilic leukocyte elastase in systemic sclerosis: association with pulmonary fibrosis

OBJECTIVE

To determine the serum concentrations and clinical association of polymorphonuclear neutrophilic leukocyte (PMN) elastase in patients with systemic sclerosis (SSc).

METHODS

Serum PMN elastase levels from 21 patients with limited cutaneous SSc (lSSc) and 32 with diffuse cutaneous SSc (dSSc) were examined by ELISA.

RESULTS

Serum PMN elastase levels were elevated in patients with SSc, especially dSSc, compared to healthy controls. SSc patients with elevated serum PMN elastase levels had more frequent presence of pulmonary fibrosis, arthritis, contracture of phalanges, and diffuse pigmentation. Anticentromere antibody was detected less frequently in SSc patients with elevated serum PMN elastase levels than in controls. Consistently, serum PMN elastase levels also correlated positively with serum levels of KL-6 and surfactant protein-D, serological markers for pulmonary fibrosis. Serum PMN elastase levels were also associated with levels of serum 8-isoprostane, an oxidative stress marker in SSc.

CONCLUSION

Serum PMN elastase levels were elevated in patients with SSc, and it was more prominent in patients with pulmonary fibrosis, suggesting that serum PMN elastase is a novel serological marker for SSc-related pulmonary fibrosis.

Surfactant protein D and KL-6 as serum biomarkers of interstitial lung disease in patients with scleroderma

OBJECTIVE

To assess whether serum concentrations of surfactant protein D (SP-D) and Krebs von den Lungen-6 (KL-6), glycoproteins expressed by type II pneumocytes, correlate with the presence of "alveolitis" and measures of lung function in patients enrolled in the Scleroderma Lung Study (SLS).

METHODS

Serum obtained at baseline screening of patients with systemic sclerosis (SSc, scleroderma) in the SLS was assayed. "Alveolitis" was defined by either bronchoalveolar lavage or thoracic high-resolution computed tomography (HRCT) by SLS criteria. SP-D and KL-6 levels were measured by ELISA in 66 SSc patients (44 with "alveolitis," 22 without "alveolitis") and in 10 healthy controls. These were compared to clinical measures of lung disease and "alveolitis" in the SLS patients.

RESULTS

SP-D levels were 300+/-214 ng/ml (mean+/-SD) in the SSc patients compared to 40+/-51 ng/ml in controls (p<0.0001). KL-6 levels were 1225+/-984 U/ml in the SSc patients and 333+/-294 U/ml in controls (p<0.0001). SSc patients with "alveolitis" had higher levels of both SP-D and KL-6 than those without "alveolitis." The level of SP-D was 353+/-219 ng/ml in patients with "alveolitis" and 161+/-143 ng/ml without "alveolitis" (p=0.0002). The level of KL-6 was 1458+/-1070 U/ml in patients with "alveolitis" and 640+/-487 U/ml without "alveolitis" (p=0.0001). Receiver operator characteristic curve analysis demonstrated high sensitivity and specificity of both SP-D and KL-6 for the determination of "alveolitis." KL-6 and SP-D were positively correlated with maximum fibrosis scores, but not with maximum ground-glass opacities, on HRCT.

CONCLUSION

Serum levels of SP-D and KL-6 appear to be indicative of "alveolitis" in SSc patients as defined by the SLS, and are significantly higher than in SSc patients without "alveolitis." Serum SP-D and KL-6 may serve as noninvasive serological means of assessing interstitial lung disease in patients with SSc.

Interstitial lung disease in systemic sclerosis

Lung involvement frequently complicates systemic sclerosis (SSc), provoking loss of quality of life and a poor expectation of survival. For this reason an early diagnosis of lung involvement is warranted: high-resolution computed tomography (HRCT), pulmonary function tests (PFT), lung scintigraphy with DTPA and bronchoalveolar lavage (BAL) are mandatory to define and follow-up pulmonary interstitium. Coughing and a sensation of breathlessness on exertion are the earliest symptoms of lung involvement. Lung involvement may be investigated with PFTs, which are non-invasive and require breathing into a tube via a mouthpiece. Forced vital capacity, which measures the total amount of air capable of being blown forcefully, and the diffusion capacity for carbon monoxide, a measure of how well oxygen diffuses into blood, are the most important functional measures. A routine chest X-ray may demonstrate fibrosis, but it is not very sensitive for detecting early or mild disease. For this reason, a HRCT scan is required. This non-invasive investigation provides images of multiple slices through the lung, from top (apex) to bottom (base), and can even detect lung involvement in early phases when no symptoms are present. (99m)T-DTPA is recommended in those patients with isolated diffusion deficits on lung function tests and in addition to HRCT in confirming the suspicion of vascular disease rather than early fibrosing alveolitis. Bronchoscopy with BAL is an invasive test that also may provide information about the inflammatory status of the affected areas of the lung detected during HRCT. In order to detect alveolitis, it should be performed as early as possible, to start prompt immunosuppressive treatment.

New developments in scleroderma interstitial lung disease

PURPOSE OF REVIEW

To review the recent medical literature pertaining to interstitial lung disease found in association with systemic sclerosis remains a major contributor to morbidity and mortality. Significant progress is being made in terms of understanding the pathogenesis, the best approaches to clinical evaluation, and various options for therapy of systemic sclerosis patients whose disease course is complicated by interstitial lung disease.

RECENT FINDINGS

Recent studies highlight the importance of microvascular disease, autoimmunity, and fibroblast differentiation/activation in the pathogenesis of systemic sclerosis-interstitial lung disease, particularly in the early phase of disease. It appears as if the balance between various pro-fibrotic/pro-inflammatory and anti-fibrotic/anti-inflammatory mediators may be central to interstitial lung disease pathogenesis, which presents potential opportunities for therapeutic intervention. The clinical approach to staging of disease activity remains controversial. High resolution computed tomography scans, bronchoalveolar lavage and various serum markers (e.g., surfactant protein D and KL-6) each may provide useful information about the degree of activity of the systemic sclerosis-interstitial lung disease. Currently, treatment recommendations are limited by a scarcity of well designed clinical trials, but the recently completed Scleroderma Lung Study is a model for future studies and is providing useful information about this important complication of systemic sclerosis.

SUMMARY

Basic and clinical studies of systemic sclerosis patients with interstitial lung disease are yielding promising data that ultimately will be translated in to more effective diagnostic and therapeutic strategies.

Serum pulmonary and activation-regulated chemokine/CCL18 levels in patients with systemic sclerosis: a sensitive indicator of active pulmonary fibrosis

OBJECTIVE

To clarify the clinical significance of serum levels of pulmonary and activation-regulated chemokine (PARC) in the diagnosis and monitoring of pulmonary fibrosis (PF) in patients with systemic sclerosis (SSc) and to compare PARC levels with KL-6 antigen or surfactant protein D (SP-D) levels.

METHODS

Serum PARC levels were determined by enzyme-linked immunosorbent assay in 123 SSc patients. In a retrospective longitudinal study, correlation of serum PARC levels with the activity of PF was assessed in 21 SSc patients with active PF.

RESULTS

PARC levels at the first visit were higher in patients with SSc than in patients with systemic lupus erythematosus (SLE) or healthy controls. Increased serum PARC levels were associated with involvement of PF, decreased diffusing capacity for carbon monoxide, and decreased vital capacity in SSc patients. In the longitudinal study, serum PARC levels were significantly decreased in SSc patients with inactive PF compared with those with active PF.

CONCLUSION

Elevated serum PARC levels correlated with PF and more sensitively reflected the PF activity than did serum KL-6 or SP-D levels in SSc. Serum PARC levels may be a useful new serum marker for active PF in SSc.

Clinical aspects of lung involvement: lessons from idiopathic pulmonary fibrosis and the scleroderma lung study

Interstitial lung disease (ILD) occurs frequently among patients with systemic slcerosis (SSc) and accounts for significant morbidity and mortality. SSc-ILD resembles idiopathic pulmonary fibrosis (IPF) in many respects; each is characterized by a restrictive ventilatory defect that results from an active fibrosing process in the lung interstitium, and each is characterized by ground glass opacification on high resolution computed tomography (HRCT) and inflammatory cells in bronchoalveolar lavage fluid (BALF). Differences in the classification of lung histo-pathology are noted frequently and may account for some of the difference in outcome for patients with SSc-ILD and IPF. Optimal treatment of SSc-ILD remains to be determined, but cyclophosphamide has been reported to be effective in a number of case series. A randomized controlled trial, the Scleroderma Lung Study (SLS), will be completed in 2005; the outcome of the SLS should define the efficacy of daily oral cyclophosphamide for SSc-ILD patients with alveolitis defined by BALF and HRCT.

Life-threatening dermatoses due to connective tissue disorders

Connective tissue disorders such as scleroderma, dermatomyositis and lupus erythematosus are autoimmune, multi-system disorders whose clinical manifestations can be restricted to the skin or may involve many organs. The degree and rate of organ system involvement defer, as does the prognosis and rapidity of disease progression. In this article, scleroderma, dermatomyositis and lupus erythematosus will be reviewed in respect to their life-threatening potential.

Fibrosing alveolitis in systemic sclerosis: the need for early screening and treatment

Abnormalities in lung function occur in 70% of patients with systemic sclerosis (SSc). Fibrosing alveolitis in SSc (FASSc) is more commonly seen in the diffuse cutaneous form of SSc, particularly in the presence of antitopoisomerase antibodies (Scl70), and with the decreasing incidence of scleroderma renal crisis it is now the major cause of mortality in this patient population. Screening of patients recently diagnosed with SSc by pulmonary function tests and the performance of high resolution computed tomography when physiological abnormalities are identified has resulted in the identification of significant numbers of patients with early, asymptomatic FASSc. Whether these patients should be further investigated with a surgical lung biopsy or receive immunosuppression is unclear, because it cannot yet be reliably predicted who will develop progressive disease and the evidence to support the efficacy of treatment is not strong. The objective of the present article was to review the evidence to support the use of immunosuppressive therapy in FASSc and, based on these data, to propose an algorithm for the investigation and management of this difficult clinical problem.

Elevated exhalation of hydrogen peroxide in patients with systemic sclerosis

BACKGROUND

Systemic sclerosis is accompanied by an influx of activated phagocytes into distal airways. These cells release H2O2, which may evaporate from the airways surface and be detected in expired breath condensate. We tested whether patients with systemic sclerosis exhale more H2O2 than healthy subjects and whether breath condensate H2O2 levels correlate with some clinical parameters.

MATERIAL AND METHODS

H2O2 was measured fluorimetrically in the expired breath condensate of 27 patients (22 women, five men, mean age 49 +/- 13.1 years) with systemic sclerosis and 27 age- and sex- matched healthy controls.

RESULTS

Exhaled H2O2 levels were 3.5-fold higher (0.88 +/- 0.62 microM vs. 0.25 +/- 0.17 microM, P < 0.001) in the patients with systemic sclerosis than in the controls. Treatment with cyclophosphamide and/or prednisone (29 +/- 50 months, range 3-168 months) did not significantly decrease H2O2 exhalation (0.78 +/- 0.50 microM, n= 10 vs. 0.94 +/- 0.67 microM, n= 17, P > 0.05). No significant difference was found between patients with limited and diffuse scleroderma (1.03 +/- 0.69 microM, n= 17 vs. 0.63 +/- 0.41 microM, n= 10, P > 0.05). H2O2 levels correlated with disease duration (r = 0.38, P < 0.05) and time from the first Raynaud's episode (r = 0.44, P < 0.05).

CONCLUSIONS

Patients with systemic sclerosis exhale more H2O2 than healthy controls, suggesting involvement of reactive oxygen species in disease processes. Lack of significant intergroups differences in H2O2 levels may have resulted from the small number of patients analyzed.

Serum KL-6 levels in patients with pulmonary complications after allogeneic bone marrow transplantation

KL-6, a mucinous high-molecular weight glycoprotein expressed on type 2 pneumocytes, has been shown to be elevated in the serum and bronchoalveolar lavage fluid of patients with interstitial pneumonitis (IP). We measured the serum levels of KL-6 in patients after they had undergone allogeneic bone marrow transplantation (BMT) to determine whether KL-6 could be a clinically useful indicator for the development of IP. The serum concentrations of KL-6 were determined by a sandwich-type enzyme-linked immunosorbent assay using an anti-KL-6 monoclonal antibody. A total of 1028 samples were tested from 76 patients (78 transplantations) who received BMTs. The KL-6 values were markedly elevated in patients with pulmonary complications, but not in those with acute and chronic graft-versus-host disease, hemorrhagic cystitis, herpes encephalitis, sepsis, and veno-occlusive disease. The serum levels of KL-6 from patients with pulmonary complications were significantly higher than from those without pulmonary complications (P < .001) and those with other complications (P < .001). Of the 12 patients with pulmonary complications, 6 had idiopathic IP (IIP). The levels were not high at the onset of IIP. Four of 6 IIP patients showed marked elevations of KL-6 levels in parallel with the severity of IP and died of respiratory failure without response to treatment. Assessment of serum KL-6 levels might not be useful for the early diagnosis of IP, but may be a useful indicator for monitoring the severity of IP after BMT.

Surfactant protein D (SP-D) and systemic scleroderma (SSc)

We measured serum levels of SP-D in collagen diseases (110 cases) such as systemic scleroderma (SSc), scleroderma spectrum disorders (SSD), systemic lupus erythematodes (SLE), Sjogren syndrome (Sjs), dermatomyositis (DM), rheumatoid arthritis (RA), and dermatitis (DE) (109 cases) as a control. Additionally, we performad a correlation analysis to determine how these levels were related to pulmonary fibrosis and function test (vital capacity, %DLco). The serum levels of SP-D increased in SSc patients with Barnett type III more than in SSc patients with Barnett type I or II, while they increased slightly in SSD (incomplete type of SSc) patients. The differences in these figures were statistically significant between the SSc (SSc & SSD) and non-SSc (SLE, DM, Sjs & RA) groups (p<0.005). The serum levels of SP-D in SSc patients with anti-topoisomerase I antibodies were statistically higher than those in SSc patients with other types of anti-nuclear antibodies. There was a statistically significant correlation between the severity of pulmonary fibrosis and the serum levels of SP-D, and a statistically negative correlation between SP-D levels and vital capacity or %DLco, but there was no proportional correlation with the forced expiatory volume (FEV1.0%). There was no statistical relationship between pre- and post-therapy with photopheresis; however, there was a statistical correlation between the serum levels of SPD and KL-6. In the group of collagen diseases, plasma levels of SP-D were higher than serum levels of SP-D. Patients with SSc possess higher levels of SP-D than do those with other collagen diseases and dermatitis, which may correspond to the severity of pulmonary fibrosis.