Radiological and functional assessment of pulmonary involvement in the rheumatoid arthritis patients

Exploring pulmonary involvement in newly diagnosed rheumatoid arthritis, and psoriatic arthritis: a single center study

OBJECTIVES

This cross-sectional study aimed to determine the prevalence, manifestation, and risk factors of pulmonary involvement in newly diagnosed, untreated rheumatoid arthritis (RA) and psoriatic arthritis (PsA) patients, and to evaluate the efficacy of various diagnostic tools in screening for pulmonary involvement.

METHODS

Untreated, newly diagnosed patients with RA and PsA underwent an extensive multimodal diagnostic approach including clinical and laboratory assessment, pulmonary function tests, and chest radiography.

RESULTS

We recruited 50 arthritis patients (26 RA, 24 PsA) and 26 control subjects. Respiratory symptoms were found in 36.0 % of arthritis patients and 11.5 % of controls (p = 0.031). Pathologically reduced breathing width (< 3.0 cm) was significantly more common in arthritis patients (64.0 %) than in controls (23.1 %) (p < 0.001). Pulmonary function test results did not differ significantly between groups. Chest radiography revealed pulmonary involvement in 37.0 % of arthritis patients, higher in RA (50.0 %) than in PsA (22.7 %). Notably, only 35.3 % of arthritis patients with radiographic pulmonary involvement were symptomatic, with 64.7 % being asymptomatic. Radiographic pulmonary involvement was associated with advanced age (p = 0.002) and increased rheumatoid factor levels (p = 0.024).

CONCLUSION

Our research underscores the significant prevalence of largely asymptomatic pulmonary involvement in newly diagnosed RA and PsA patients. These findings highlight the importance of an early, multidisciplinary screening approach, particularly for high-risk individuals. Further large-scale studies are needed to develop comprehensive screening protocols to improve early detection and treatment of pulmonary involvement in arthritis.

Design of ANCHOR-RA: a multi-national cross-sectional study on screening for interstitial lung disease in patients with rheumatoid arthritis

BACKGROUND

Patients with rheumatoid arthritis (RA) are at risk of developing interstitial lung disease (ILD), which is associated with high mortality. Screening tools based on risk factors are needed to decide which patients with RA should be screened for ILD using high-resolution computed tomography (HRCT). The ANCHOR-RA study is a multi-national cross-sectional study that will develop a multivariable model for prediction of RA-ILD, which can be used to inform screening for RA-ILD in clinical practice.

METHODS

Investigators will enrol consecutive patients with RA who have ≥ 2 of the following risk factors for RA-ILD: male; current or previous smoker; age ≥ 60 years at RA diagnosis; high-positive rheumatoid factor and/or anti-cyclic citrullinated peptide (titre > 3 x upper limit of normal); presence or history of certain extra-articular manifestations of RA (vasculitis, Felty's syndrome, secondary Sjögren's syndrome, cutaneous rheumatoid nodules, serositis, and/or scleritis/uveitis); high RA disease activity in the prior 12 months. Patients previously identified as having ILD, or who have had a CT scan in the prior 2 years, will not be eligible. Participants will undergo an HRCT scan at their local site, which will be assessed centrally by two expert radiologists. Data will be collected prospectively on demographic and RA-related characteristics, patient-reported outcomes, comorbidities and pulmonary function. The primary outcomes will be the development of a probability score for RA-ILD, based on a multivariable model incorporating potential risk factors commonly assessed in clinical practice, and an estimate of the prevalence of RA-ILD in the study population. It is planned that 1200 participants will be enrolled at approximately 30 sites in the USA, UK, Germany, France, Italy, Spain.

DISCUSSION

Data from the ANCHOR-RA study will add to the body of evidence to support recommendations for screening for RA-ILD to improve detection of this important complication of RA and enable early intervention.

TRIAL REGISTRATION

clinicaltrials.gov NCT05855109 (submission date: 3 May 2023).

Identification, Monitoring, and Management of Rheumatoid Arthritis-Associated Interstitial Lung Disease

Interstitial lung disease (ILD) is a frequent complication of rheumatoid arthritis (RA) that is associated with a significant increase in mortality. Several risk factors for the development of ILD in patients with RA have been identified, but ILD can still develop in the absence of these risk factors. Screening tools for RA-ILD are required to facilitate early detection of RA-ILD. Close monitoring of patients with RA-ILD for progression is crucial to enable timely implementation of treatment strategies to improve outcomes. Patients with RA are commonly treated with immunomodulatory therapies, although their efficacy in slowing the progression of RA-ILD remains the subject of debate. Clinical trials have shown that antifibrotic therapies slow decline in lung function in patients with progressive fibrosing ILDs, including patients with RA-ILD. The management of patients with RA-ILD should be based on multidisciplinary evaluation of the severity and progression of their ILD and the activity of their articular disease. Close collaboration between rheumatologists and pulmonologists is essential to optimize patient care.

Clinical and preclinical pulmonary disease in newly diagnosed rheumatoid arthritis: a two-year follow-up study

OBJECTIVE

Pulmonary disease is a major cause of excess mortality among patients with rheumatoid arthritis (RA). Interstitial lung disease (ILD) is a feared complication, but the benefit of screening is unknown. The aim of this study was to assess the frequency of pulmonary disease, including ILD, in early RA.

METHOD

Patients with newly diagnosed RA were recruited prospectively at a single centre and underwent systematic pulmonary function tests (PFTs) and computed tomography (CT) scans at inclusion and after two years.

RESULTS

The study included 150 patients (mean age 57 years, 63% female; 59% current or former smokers). Of these, 136 underwent baseline PFTs and 137 CT. Mean forced expiratory volume in one second was 99% predicted and forced vital capacity 106%. Mean diffusing capacity of the lungs for carbon monoxide (DLCO) was 84% predicted. Frequently detected CT abnormalities were pulmonary nodules (42%), bronchiectasis (29%), and emphysema (20%). Two patients had clinically significant ILD and six had mild reticulation suggestive of preclinical ILD. No ILD progression was identified at two-year follow-up. Smoking was associated with DLCO<80% (p=0.004), combined hyperinflation and diffusion impairment (residual volume>120% and DLCO<80%) (p=0.004), and visual emphysema on CT (p<0.001).

CONCLUSION

Emphysema and bronchiectasis were common, but most patients had mild disease with preserved lung function. Preclinical or clinical ILD was seen in a minority in this early phase of RA. These findings suggest symptom-based screening and primary intervention focusing on smoking cessation rather than screening for ILD at the time of RA diagnosis.

Application of impulse oscillometry to detect interstitial lung disease and airway disease in adults with rheumatoid arthritis

BACKGROUND

We conducted a retrospective observational study to explore the potential application of impulse oscillometry (IOS) as an alternative to high-resolution computed tomography (HRCT) for detecting pulmonary involvement in patients with rheumatoid arthritis (RA) because clinically evident interstitial lung disease (ILD) and airway involvement are common in this population.

METHODS

We enrolled 72 patients with RA who underwent pulmonary function tests (PFTs) and IOS between September 2021 and September 2022. We aimed to identify the PFT and IOS variables associated with lung diseases shown on HRCT images.

RESULTS

In our cohort of 72 patients, 48 underwent HRCT; of these, 35 had airway disease or ILD and 13 showed no obvious abnormalities on HRCT. Abnormal IOS and PFT parameters were observed in 34 and 23 patients, respectively, with abnormal HRCT images. The predicted percentages for forced vital capacity, the ratio of forced expiratory volume in the first one second to forced vital capacity, and forced mid-expiratory flow value were significantly lower in patients with abnormal HRCT. Lung resistance at 5 Hz, difference in resistance between 5 and 20 Hz, resonant frequency (Fres), and reactance area were higher in these patients and reactance at 5 Hz was lower. Compared to other parameters, Fres > 14.14 was significantly associated with alterations in HRCT and may be used as an indicator for monitoring disease.

CONCLUSION

Fres > 14.14 is significantly associated with lung involvement in RA patients. Performance of spirometry with IOS is more beneficial than spirometry alone for evaluating lung involvement in RA patients.

Interstitial Lung Disease in Rheumatoid Arthritis: A Practical Review

Rheumatoid arthritis (RA) is a systemic inflammatory disease, which primarily causes symmetric polyarthritis. An extrarticolar involvement is common, and the commonly involved organ is lungs. Although cardiac disease is responsible for most RA-related deaths, pulmonary disease is also a major contributor, accounting for ~10-20% of all mortality. Pulmonary disease is a common (60-80% of patients with RA) extra-articular complication of RA. Optimal screening, diagnostic, and treatment strategies of pulmonary disease remain uncertain, which have been the focus of an ongoing investigation. Clinicians should regularly assess patients with RA for the signs and symptoms of pulmonary disease and, reciprocally, consider RA and other connective tissue diseases when evaluating a patient with pulmonary disease of an unknown etiology. RA directly affects all anatomic compartments of the thorax, including the lung parenchyma, large and small airways, pleura, and less commonly vessels. In addition, pulmonary infection and drug-induced lung disease associated with immunosuppressive agents used for the treatment of RA may occur.

Small airway disease and its predictors in patients with rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) is a connective tissue disease, characterized by symmetric peripheral polyarthritis. Extra-articular disease occurs in approximately 50% of the patients with lung being a common site. The presence of functional or morphological abnormalities in small airways has recently been noted in patients with RA but its exact prevalence and clinical significance is still a subject of debate. This study was aimed to determine the prevalence of small airway disease (SAD) in patients with RA and the factors influencing it.

METHODS

Fifty consecutive patients with RA were included in this cross-sectional observational study. All patients were subjected to pulmonary function tests (PFT) including Spirometry and Forced Oscillation technique (FOT). Those with features of SAD on PFT were subjected to High-Resolution Computed Tomography (HRCT) of the chest.

RESULTS

Spirometry was suggestive of SAD in 17 patients, with 34% prevalence and FOT was abnormal in 9 patients, with 18% prevalence in the study population. Of 17 patients with SAD on spirometry, 8 (47.05%) patients showed mosaic attenuation, a sign of SAD on the HRCT chest. On univariate analysis, age, Disease Activity Score (DAS-28), joint erosions on X-ray, RF and anti-CCP were found to be associated with SAD.

CONCLUSION

SAD was present in one-third of the patients with RA, even in those with short duration of disease, low to moderate disease activity and no respiratory symptoms. It is thus inferred that the complete workup of RA patients should include pulmonary function assessment.

Abatacept in rheumatoid arthritis-associated interstitial lung disease: short-term outcomes and predictors of progression

INTRODUCTION

Interstitial lung disease in rheumatoid arthritis (RA-ILD) is an extra-articular involvement that impairs the prognosis and for which there is still no well-coded treatment. The aim of this study was to evaluate abatacept (ABA) effectiveness and safety in patients with RA-ILD.

METHODS

RA-ILD patients who started ABA treatment were consecutively enrolled. Chest high-resolution computed tomography (HRCT), clinical, laboratory and respiratory function variables were collected at baseline and after 18 months of ABA treatment. HRCT abnormalities were evaluated using a computer-aided method (CaM). ABA response was established based on the change in the percentage of fibrosis evaluated at HRCT-CaM, dividing patients into "worsened" (progression ≥ 15%), "improved" (reduction ≥ 15%), and "stable" (changes within the 15% range). The multivariate regression model was used to assess the associations between RA characteristics and ABA response.

RESULTS

Forty-four patients (81% women, mean age 59.1 ± 8.0, mean disease duration of 7.5 ± 3.1 years) were studied. Five patients (11.4%) showed RA-ILD progression, 32 patients (72.6%) were considered stable, and 7 patients (16.0%) showed an RA-ILD improvement. The proportion of current smokers was significantly different between "worsened" patients, respect to those defined as "improved/stable" (p = 0.01). Current smoking habit (p = 0.005) and concomitant methotrexate treatment (p = 0.0078) were the two variables related to RA-ILD progression in multivariate regression analysis.

CONCLUSION

Treatment with ABA is associated with a RA-ILD stability or improvement in the 88.6% of patients. Current smoking habit and concomitant treatment with methotrexate are the modifiable factors associated with RA-ILD worsening. Key Points • Abatacept plays a favourable role in the control of RA-ILD, with a significant worsening in only 11.4% of patients during a 18-month follow-up period. • The predictive variables related to RA-ILD progression during abatacept therapy are the concomitant treatment with methotrexate and current smoking habit.

The Attitudes and Practices of Physicians Caring for Patients with Rheumatoid Arthritis-Interstitial Lung Disease: An International Survey

OBJECTIVES

This study sought to determine the level of understanding and opinion amongst rheumatologist and pulmonologists regarding risk factors, diagnostic approach and treatment of rheumatoid arthritis-associated interstitial lung disease (RA-ILD).

METHODS

We conducted an international electronic survey of rheumatologists and pulmonologists utilizing two separate Redcap-based surveys with questions on the epidemiology, workup and management of RA-ILD as well as ILD screening questions using case-based scenarios directed at rheumatologists. The survey also collected demographic data on participants including their practice setting, years in practice and country of practice.

RESULTS

We received a total of 616 responses (354 rheumatologists and 262 pulmonologists) from 6 continents. There were significant differences in responses between pulmonologists and rheumatologists in estimated prevalence and mortality, risk factors for the development of ILD in RA and medications that are effective or should be avoided. Rheumatologists were much less likely to consider assessment for ILD in high risk, asymptomatic patients compared with high-risk patients with either symptoms or exam findings suggestive of ILD.

CONCLUSION

Our study brought to light the variability in disease assessment and clinical practice amongst providers caring for patients with RA-ILD and indicate that greater education is needed to optimize clinical decision making in the risk assessment, screening and treatment of RA-ILD. Research questions that address appropriate screening and treatment strategies for RA-ILD will be valuable for rheumatologists given their central role in the overall health and lung health of patients with RA.

Pulmonary Manifestations of Rheumatoid Arthritis, Psoriatic Arthritis and Peripheral Spondyloarthritis: Prevalence, Diagnostic Approach and Treatment Options

Interstitial lung disease (ILD) is the most common form of pulmonary impairment in patients with rheumatoid arthritis (RA). However, patients with RA or other arthritic diseases such as psoriatic arthritis (PsA) or peripheral spondyloarthritis (pSpA) are at a higher risk of developing several other pulmonary diseases, such as chronic obstructive lung disease (COPD), compared to patients without arthritis. This review aims at summarizing the current knowledge on the prevalence of pulmonary diseases in the above-mentioned forms of arthritis, the challenges faced by prevalence studies in detecting pulmonary diseases in patients with arthritis, as well as possible treatment options. Dyspnea, cough or other pulmonary symptoms in arthritis patients should prompt gradual diagnostic procedures considering pulmonary manifestations as a major cluster of differential diagnosis. However, treatment options often lack solid evidence-based guidelines and referrals to specialized centers are often necessary.

Recent advances in rheumatoid arthritis-associated interstitial lung disease

PURPOSE OF REVIEW

To provide an overview of recent studies that could be helpful in a better understanding of rheumatoid arthritis-associated interstitial lung disease (RA-ILD) and to facilitate the clinical management of this severe complication of RA.

RECENT FINDINGS

The advances in deciphering the genetic architecture of RA-ILD support the hypothesis of RA-ILD as a complex disease with a complex phenotype encompassing at least the usual interstitial pneumonia (UIP) high-resolution CT pattern and non-UIP. Genetics studies have provided evidence for a shared genetic background in idiopathic pulmonary fibrosis (IPF) and RA-ILD, and more specifically RA-UIP, a disease with high morbidity and mortality. These findings support the rationale for common pathogenic pathways opening new avenues for future intervention in RA-ILD, notably with - drugs that proved active in IPF. In agreement, a recent controlled trial suggests efficacy of nintedanib, an antifibrotic drug, in patients with progressive lung fibrosis, including RA-ILD. However, there is a substantial gap in RA-ILD treatment, notably evaluating the effect of the RA treatments on the ILD course because of no controlled trial yet.

SUMMARY

The phenotypical, environmental, and genetic similarities between IPF and RA-ILD have led to a better understanding of the underlying pathogenesis of RA-ILD. Despite the identification of several biomarkers and useful screening tools, several questions remain unanswered regarding the identification of patients with RA at increased risk of ILD and risk of progression. Other substantial gaps are the lack of recommendations for how high-risk patients should be screened and which specific therapeutic strategy should be initiated. International collaborative efforts are needed to address these issues and develop specific recommendations for RA-ILD.

Interstitial Lung Disease in Rheumatoid Arthritis Remains a Challenge for Clinicians

Interstitial lung disease (ILD) is a serious complication of rheumatoid arthritis (RA) contributing to significantly increased morbidity and mortality. Other respiratory complications, such as chronic obstructive pulmonary disease and bronchiectasis, are frequent in RA. Infections and drug toxicity are important differential diagnoses and should be considered in the diagnostic work-up of patients with RA presenting with respiratory symptoms. This review provides an overview of the epidemiology and pathogenesis of RA-ILD, the radiological and histopathological characteristics of the disease as well as the current and future treatment options. Currently, there is no available evidence-based therapy for RA-ILD, and immunosuppressants are the mainstay of therapy. Ongoing studies are exploring the role of antifibrotic therapy in patients with progressive fibrotic ILD, which may lead to a new treatment approach for subgroups of patients with RA-ILD.

Thoracic Manifestations of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is commonly associated with pulmonary disease that can affect any anatomic compartment of the thorax. The most common intrathoracic manifestations of RA include interstitial lung disease, airway disease, pleural disease, rheumatoid nodules, and drug-induced toxicity. Patients with RA with thoracic involvement often present with nonspecific respiratory symptoms, although many are asymptomatic. Therefore, clinicians should routinely consider pulmonary disease when evaluating any patient with RA, particularly one with known risk factors. The optimal screening, diagnostic, and treatment strategies for RA-associated pulmonary disease remain uncertain and are the focus of ongoing investigation.

Pleuropulmonary manifestation in patients with rheumatoid arthritis in Saudi Arabia

BACKGROUND AND OBJECTIVES:

Pleuropulmonary (PP) involvement in rheumatoid arthritis (RA) is associated with high morbidity and mortality. Nevertheless, limited data are available regarding lung complications in the Middle East, especially in Saudi Arabia. The objectives of the current study were to determine the prevalence of PP manifestations and to identify the associated risk factors.

METHODS:

This was a retrospective study involving 419 patients diagnosed at a tertiary center over a 12.5-year period. The frequency of pulmonary manifestations was recorded based on combined results from chest X-rays, pulmonary function tests, and high-resolution computed tomography scan of the chest.

RESULTS:

The overall frequency of lung involvement was 25.8%. Pneumonia, bronchiectasis, and interstitial lung disease were the most common abnormalities (36%, 35%, and 23%, respectively). The presence of comorbid illness (odds ratio [OR]: 3.19; 95% confidence interval [CI]: 2.02–5.1), male gender (OR: 2.4; 95% CI: 1.3–4.24), and the presence of extra-articular manifestations of RA (ExRA) (OR: 2.35; 95% CI: 0.4–4.01) were predictive of lung involvement.

CONCLUSIONS:

Pneumonia, bronchiectasis, and interstitial lung disease were the most common abnormalities seen in RA patients. The presence of comorbidity, male gender, and ExRA was significantly associated with lung involvement.

Chronic inflammation and lung fibrosis: pleotropic syndromes but limited distinct phenotypes

Experimental models of lung fibrosis have been disappointing in predicting therapeutic responses to a wide variety of interventions in clinical fibrosing lung diseases. There are multiple potential reasons, but this fundamentally calls into question the validity of the models and their fidelity to clinical syndromes. We propose that the clinical diseases associated with pulmonary fibrosis, although manifesting a broad array of widely different clinical presentations and features, result in essentially two distinct phenotypes of fibrosis that we will describe. The most common and problematic of these are not effectively modeled experimentally. In this review, we present several clinical entities as examples of the phenotypic distinctions. The first two represent the extremes: postinflammatory fibrosis observed in hypersensitivity pneumonitis (HP) and dysregulated matrix deposition as observed in idiopathic pulmonary fibrosis (IPF). We also present a third clinical entity, that of lung disease associated with rheumatoid arthritis (rheumatoid lung), representing a condition that can manifest as either phenotype, and offering a potential opportunity to explore the mechanisms underlying the pathogenesis of the two distinct fibrotic phenotypes.

Treatment of interstitial lung diseases associated with connective tissue diseases

A variety of interstitial lung diseases (ILDs) have been reported in association with connective tissue diseases (CTDs). ILD is commonly associated with multiple CTDs and accounts for significant morbidity and mortality in these conditions. In rheumatoid arthritis and systemic sclerosis, ILD commonly occurs in the course of these disorders (incidence: 20-44%). The pathological findings of ILDs are similar to those of idiopathic interstitial pneumonia. A wide variety of histopathologic features, such as various types of interstitial pneumonia and airway involvement, have been observed that are specific for ILDs in rheumatoid arthritis, and this high variety makes its pathology complicated. The diagnosis of ILD is generally based on clinical presentation, bronchioalveolar lavage fluid and high-resolution computed tomography, among others. The most important differential diagnosis is infection, especially pneumocystis pneumonia, and treatment-related toxic damage. The immunosuppressive agents most widely used for the treatment of ILDs are cyclophosphamide, azathioprine, mycophenolate mofetil and calcineurin inhibitors. Other therapeutic strategies are currently being extensively studied, such as antifibrotic agents, endothelin-1 receptor antagonists, tyrosine kinase inhibitors and newer biological agents. In this article, we describe novel therapies for ILDs associated with CTDs.

Rheumatoid arthritis-associated interstitial lung disease

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

Respiratory symptoms in rheumatoid arthritis: relation to pulmonary abnormalities detected by high-resolution CT and pulmonary functional testing

Pulmonary disease is the most frequent and among the most severe extra-articular manifestation of rheumatoid arthritis (RA). However, this issue has not been sufficiently studied in Egyptian patients. The objectives of the present study are to investigate the prevalence and types of pulmonary involvement using high-resolution computed tomography scan (HRCT) and pulmonary function tests (PFT) and evaluate the association between respiratory symptoms and RA-lung disease in a group of Egyptian RA patients. Thirty-six RA patients were recruited; 34 females (94.4%) and 2 males (5.6%) with median age of 48.5 years, and none of them was smoker. Detailed medical and drug histories were obtained. PFT, plain X-ray of the chest, and HRCT were performed to all subjects involved. Nearly 64% of RA patients demonstrated abnormalities in PFT and 47% in HRCT. Mixed restrictive and obstructive pattern was the commonest. Nearly two-thirds of our patients reported one or more pulmonary symptom whether dyspnea, cough, wheezing, or phlegm. Dyspnea was the most frequent symptom. Respiratory symptoms were statistically more common in patients with lung disease. The advanced age, high radiological score, and severity of rheumatoid disease were found to be predictive of lung involvement. Among respiratory symptoms, dyspnea and cough were associated with any pulmonary abnormalities. When specific pulmonary abnormalities were considered, only dyspnea was identified as predictor for restriction. For obstructive abnormality, both cough and wheezing provided valid prediction. We conclude that pulmonary involvement is a common manifestation in Egyptian RA patients, and the pattern of involvement is generally consistent with other studies that were performed worldwide. Specific respiratory symptoms could be used as practical, easy, and cost-effective method, especially in older and with more severe RA patients, to discriminate patients in need of subsequent PFT and HRCT imaging.

Small airway obstruction in patients with rheumatoid arthritis

This work was intended to evaluate the prevalence of obstructive small-airway disease in patients with rheumatoid arthritis (RA) and its association with clinical characteristics. Pulmonary function testing (PFT) and high-resolution computed tomography (HRCT) were performed on 189 consecutive RA patients. Each case was diagnosed based on abnormal HRCT findings. We defined obstructive dysfunction of small airways as a forced expiratory flow from 25% to 75% of vital capacity (FEF(25-75)) value >1.96 residual standard deviation (RSD) below predicted values. We found 19 patients (10.1%) with an interstitial pneumonia (IP) pattern and 15 (7.9%) with a bronchiolitis pattern; the other 155 (82.0%) had no abnormal HRCT patterns. In patients with neither abnormal pattern, median values of percentage predicted for carbon monoxide diffusing capacity (DL(CO)) and ratio of DL(CO) to alveolar ventilation (DLco/VA) were within the normal range, but median FEF(25-75), forced expiratory flow at 25% of vital capacity (V(25)), and V(25)/height were <70% of predicted values. Forty-seven patients (30.3%) in this group had obstructive small-airway dysfunction. Multivariate logistic regression analysis indicated that this type of abnormality is strongly associated with respiratory symptoms [odds ratio (OR) 5.18; 95% confidence interval (CI) 1.70-15.75; p = 0.012), smoking history (OR 2.78; 95% CI 1.10-6.99; p = 0.03), and disease duration >10 years (OR 2.86; 95% CI 1.27-6.48; p = 0.012). Parenchymal micronodules, bronchial-wall thickening, and bronchial dilatation on HRCT scans were also predictive factors for abnormal FEF(25-75), although these morphological changes were too limited for us to diagnose these patients with the bronchiolitis pattern. Obstructive dysfunction of small airways is apparently common among RA patients, even among those with neither the IP nor the bronchiolitis pattern on HRCT scans. Factors significantly associated with abnormal FEF(25-75) are respiratory symptoms, smoking history, and RA duration.

A towards-multidimensional screening approach to predict candidate genes of rheumatoid arthritis based on SNP, structural and functional annotations

Background

According to the Genetic Analysis Workshops (GAW), hundreds of thousands of SNPs have been tested for association with rheumatoid arthritis. Traditional genome-wide association studies (GWAS) have been developed to identify susceptibility genes using a "most significant SNPs/genes" model. However, many minor- or modest-risk genes are likely to be missed after adjustment of multiple testing. This screening process uses a strict selection of statistical thresholds that aim to identify susceptibility genes based only on statistical model, without considering multi-dimensional biological similarities in sequence arrangement, crystal structure, or functional categories/biological pathways between candidate and known disease genes.

Methods

Multidimensional screening approaches combined with traditional statistical genetics methods can consider multiple biological backgrounds of genetic mutation, structural, and functional annotations. Here we introduce a newly developed multidimensional screening approach for rheumatoid arthritis candidate genes that considers all SNPs with nominal evidence of Bayesian association (BFLn > 0), and structural and functional similarities of corresponding genes or proteins.

Results

Our multidimensional screening approach extracted all risk genes (BFLn > 0) by odd ratios of hypothesis H₁ to H₀, and determined whether a particular group of genes shared underlying biological similarities with known disease genes. Using this method, we found 6614 risk SNPs in our Bayesian screen result set. Finally, we identified 146 likely causal genes for rheumatoid arthritis, including CD4, FGFR1, and KDR, which have been reported as high risk factors by recent studies. We must denote that 790 (96.1%) of genes identified by GWAS could not easily be classified into related functional categories or biological processes associated with the disease, while our candidate genes shared underlying biological similarities (e.g. were in the same pathway or GO term) and contributed to disease etiology, but where common variations in each of these genes make modest contributions to disease risk. We also found 6141 risk SNPs that were too minor to be detected by conventional approaches, and associations between 58 candidate genes and rheumatoid arthritis were verified by literature retrieved from the NCBI PubMed module.

Conclusions

Our proposed approach to the analysis of GAW16 data for rheumatoid arthritis was based on an underlying biological similarities-based method applied to candidate and known disease genes. Application of our method could identify likely causal candidate disease genes of rheumatoid arthritis, and could yield biological insights that not detected when focusing only on genes that give the strongest evidence by multiple testing. We hope that our proposed method complements the "most significant SNPs/genes" model, and provides additional insights into the pathogenesis of rheumatoid arthritis and other diseases, when searching datasets for hundreds of genetic variances.