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Polygenic Risk Scores have high diagnostic capacity in ankylosing spondylitis

OBJECTIVE

We sought to test the hypothesis that Polygenic Risk Scores (PRSs) have strong capacity to discriminate cases of ankylosing spondylitis (AS) from healthy controls and individuals in the community with chronic back pain.

METHODS

PRSs were developed and validated in individuals of European and East Asian ethnicity, using data from genome-wide association studies in 15 585 AS cases and 20 452 controls. The discriminatory values of PRSs in these populations were compared with other widely used diagnostic tests, including C-reactive protein (CRP), HLA-B27 and sacroiliac MRI.

RESULTS

In people of European descent, PRS had high discriminatory capacity with area under the curve (AUC) in receiver operator characteristic analysis of 0.924. This was significantly better than for HLA-B27 testing alone (AUC=0.869), MRI (AUC=0.885) or C-reactive protein (AUC=0.700). PRS developed and validated in individuals of East Asian descent performed similarly (AUC=0.948). Assuming a prior probability of AS of 10% such as in patients with chronic back pain under 45 years of age, compared with HLA-B27 testing alone, PRS provides higher positive values for 35% of patients and negative predictive values for 67.5% of patients. For PRS, in people of European descent, the maximum positive predictive value was 78.2% and negative predictive value was 100%, whereas for HLA-B27, these values were 51.9% and 97.9%, respectively.

CONCLUSIONS

PRS have higher discriminatory capacity for AS than CRP, sacroiliac MRI or HLA-B27 status alone. For optimal performance, PRS should be developed for use in the specific ethnic groups to which they are to be applied.

Allele frequency spectrum of known ankylosing spondylitis associated variants in a Swedish population

Objective: The genetic predisposition to ankylosing spondylitis (AS) has been most widely studied in cohorts with European ancestry. However, within Europe, disease prevalence is higher in Sweden. Given this, we aimed to characterize known AS susceptibility variants in a homogeneous Swedish data set, assessing reproducibility and direction of effect.Method: The power to detect association within an existing Swedish targeted sequencing study (381 controls; 310 AS cases) was examined, and a set of published associations (n = 151) was intersected with available genotypes. Association to disease was calculated using logistic regression accounting for population structure, and HLA-B27 status was determined with direct polymerase chain reaction genotyping.Results: The cases were found to be 92.3% HLA-B27 positive, with the data set showing ≥ 80% predictive power to replicate associations, with odds ratios ≥ 1.6 over a range of allele frequencies (0.1-0.7). Thirty-four markers, representing 23 gene loci, were available for investigation. The replicated variants tagged MICA and IL23R loci (p < 1.47 × 10^-3), with variable direction of effect noted for gene loci IL1R1 and MST1.Conclusion: The Swedish data set successfully replicated both major histocompatibility complex (MHC) and non-MHC loci, and revealed a different replication pattern compared to discovery data sets. This was possibly due to population demographics, including HLA-B27 frequency and measured comorbidities.

Novel approaches to develop biomarkers predicting treatment responses to TNF-blockers

Introduction: Chronic inflammatory diseases (CIDs) cause significant morbidity and are a considerable burden for the patients in terms of pain, impaired function, and diminished quality of life. Important progress in CID treatment has been obtained with biological therapies, such as tumor-necrosis-factor blockers. However, more than a third of the patients fail to respond to these inhibitors and are exposed to the side effects of treatment, without the benefits. Therefore, there is a strong interest in developing tools to predict response of patients to biologics. Areas covered: The authors searched PubMed for recent studies on biomarkers for disease assessment and prediction of therapeutic responses, focusing on the effect of TNF blockers on immune responses in spondyloarthritis (SpA), and other CID, in particular rheumatoid arthritis and inflammatory bowel disease. Conclusions will be drawn about the possible development of predictive biomarkers for response to treatment. Expert opinion: No validated biomarker is currently available to predict treatment response in CID. New insight could be generated through the development of new bioinformatic modeling approaches to combine multidimensional biomarkers that explain the different genetic, immunological and environmental determinants of therapeutic responses.

Peripheral spondyloarthritis: a neglected entity-state of the art

Peripheral spondyloarthritis (pSpA) refers to a number of seemingly different spondyloarthritis subsets in which psoriatic arthritis (PsA) is the most common, and symptoms of arthritis, enthesitis or dactylitis predominate the clinical presentation. Although formal classification criteria for pSpA have been introduced in 2011, only a minority of epidemiological and clinical studies addressed this clinical entity as a separate disease. Moreover, research on outcome measures and treatment modalities in pSpA has been mainly focused on PsA. Subsequently, all biological treatments are off-label in patients with non-psoriatic pSpA. Its neglected status has important implications for clinical practice since the emerging group of early-diagnosed non-psoriatic pSpA patients remains poorly characterised and lacks specific treatment recommendations. This review summarises what is currently known regarding pSpA in terms of epidemiology, clinical presentation, diagnosis and therapeutic approach.

[Medical care situation of patients with ankylosing spondylitis and psoriatic arthritis in Germany : Medical care situation of patients with spondyloarthritis (SpA): ankylosing spondylitis (AS) and psoriatic arthritis (PsA) from the perspective of rheumatologists in private practice and hospitals in Germany-Results of the research project "SpA Loop-Life of Outpatients"]

BACKGROUND

The prevalence of spondyloarthritis (SpA) in Germany is approximately 1-1.4% and includes predominantly axial SpA (axSpA) and predominantly peripheral SpA. Ankylosing spondylitis (AS) belongs to the group of axial SpA but also exhibits peripheral manifestations. Psoriatic arthritis (PsA) can show purely peripheral or also axial manifestations. The total prevalence of SpA in Germany is approximately 1‑1.4%, the prevalence of AS is ca. 0.5% and PsA 0.2-1.4%. Patients with AS are mainly treated by internal medical rheumatologists but in many places also basically treated by general practitioners and orthopedists. Patients with PsA are mainly diagnosed and treated by rheumatologists and dermatologists working in private practice or in clinical settings. Besides the control of inflammatory activity and prevention or slowing down of the characteristic disease progression, including irreversible structural changes, the main objectives of patients as well as treating physicians are particularly freedom from pain and a quality of life comparable to non-affected persons. Decisive for successful treatment are an early diagnosis and initiation of adequate therapy as well as regular monitoring of disease activity including treatment adjustment taking the needs of the patient into consideration; however, it is unknown how often this is actually successful in routine daily practice in Germany.

OBJECTIVE

The aim of the SpA Loop research project was to display the current medical care situation of patients with AS and PsA treated in private practices and hospitals for rheumatology in Germany focusing on patient/physician profiles as well as the diagnostics and treatment.

MATERIAL AND METHODS

The instrument for the survey was a standardized questionnaire with 29 multiple choice and perception questions that was distributed to medical specialists in the field of internal medicine and rheumatology.

RESULTS

A high accordance between rheumatologists in private practice and in hospitals was observed with respect to the presentation and perception of the current medical care situation for patients with AS and PsA in Germany. Differences were only occasionally found.

CONCLUSION

The results of this research project reflect the current status of the medical care situation of AS and PsA patients in Germany. They provide information on which areas of the medical care situation can selectively be improved as well as on interesting aspects and points of discussion with respect to the patient population treated.

Transcriptome analysis of ankylosing spondylitis patients before and after TNF-α inhibitor therapy reveals the pathways affected

Tumor necrosis factor-α (TNF-α) inhibitors are highly effective in suppressing inflammation in ankylosing spondylitis (AS) patients, and operate by suppression of TFN-α and downstream immunological pathways. To determine the mechanisms of action of TNF-α inhibitors in AS patients, we used transcriptomic and bioinformatic approaches on peripheral blood mononuclear cells from AS patients pre and post treatment. We found 656 differentially expressed genes, including the genome-wide significant AS-associated genes, IL6R, NOTCH1, IL10, CXCR2 and TNFRSF1A. A distinctive gene expression profile was found between male and female patients, mainly because of sex chromosome-linked genes and interleukin 17 receptor C, potentially accounting for the differences in clinical manifestation and treatment response between the genders. In addition to immune and inflammation regulatory pathways, like intestinal immune network for IgA production, cytokine-cytokine receptor interaction, Ras signaling pathway, allograft rejection and hematopoietic cell lineage, KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analyses revealed that infection-associated pathways (influenza A and toxoplasmosis) and metabolism-associated pathways were involved in response to TNF-α inhibitor treatment, providing insight into the mechanism of TNF-α inhibitors.

Genetic markers as a predictive tool based on statistics in medical practice: ethical considerations through the analysis of the use of HLA-B(*)27 in rheumatology in France

INTRODUCTION

The use of genetic predictive markers in medical practice does not necessarily bear the same kind of medical and ethical consequences than that of genes directly involved in monogenic diseases. However, the French bioethics law framed in the same way the production and use of any genetic information. It seems therefore necessary to explore the practical and ethical context of the actual use of predictive markers in order to highlight their specific stakes. In this study, we document the uses of HLA-B(*)27, which are an interesting example of the multiple features of genetic predictive marker in general medical practice.

MATERIALS AND METHODS

The aims of this monocentric and qualitative study were to identify concrete and ethical issues of using the HLA-B(*)27 marker and the interests and limits of the legal framework as perceived by prescribers. In this regard, a thematic and descriptive analysis of five rheumatologists' semi-structured and face-to-face interviews was performed.

RESULTS

According to most of the interviewees, HLA-B(*)27 is an "overframed" test because they considered that this test is not really genetic or at least does not have the same nature as "classical genetic tests"; HLA-B(*)27 is not concerned by the ethical challenges of genetic test; the major ethics stake of this marker is not linked to its genetic nature but rather to the complexity of the probabilistic information. This study allows also showing that HLA-B(*)27, validated for a certain usage, may be used in different ways in practice.

DISCUSSION

This marker and its clinical uses underline the challenges of translating both statistical concepts and unifying legal framework in clinical practice. This study allows identifying some new aspects and stakes of genetics in medicine and shows the need of additional studies about the use of predictive genetic markers, in order to provide a better basis for decisions and legal framework regarding these practices.

Identification of multiple risk variants for ankylosing spondylitis through high-density genotyping of immune-related loci

Ankylosing spondylitis is a common, highly heritable inflammatory arthritis affecting primarily the spine and pelvis. In addition to HLA-B*27 alleles, 12 loci have previously been identified that are associated with ankylosing spondylitis in populations of European ancestry, and 2 associated loci have been identified in Asians. In this study, we used the Illumina Immunochip microarray to perform a case-control association study involving 10,619 individuals with ankylosing spondylitis (cases) and 15,145 controls. We identified 13 new risk loci and 12 additional ankylosing spondylitis-associated haplotypes at 11 loci. Two ankylosing spondylitis-associated regions have now been identified encoding four aminopeptidases that are involved in peptide processing before major histocompatibility complex (MHC) class I presentation. Protective variants at two of these loci are associated both with reduced aminopeptidase function and with MHC class I cell surface expression.

Seronegative spondyloarthritis

Seronegative spondyloarthritis (SpA) is a group of inflammatory rheumatic diseases with common clinical and aetiological features, including axial and peripheral inflammatory arthritis, enthesitis, extra-articular manifestations and a close link to the presence of the human leucocyte antigen (HLA)-B27 epitope. Ankylosing spondylitis is the most common of the SpA diseases, with prevalence in the Caucasian population ranging between 0.15% and 1.8%, generally higher in populations with a higher background prevalence of HLA-B27 positivity. Incidence has been estimated between 0.49 (Japan) and 10 (Norway) per 100,000. The prevalence of psoriatic arthritis ranges from 0.02% to 0.2%, and the incidence in the normal population is 7.2 per 100,000 per year. In patients with existing psoriasis, the prevalence of psoriatic arthritis rises to 6-42%. The prevalence of reactive arthritis is dependent on the background incidence of gastrointestinal or genitourinary infections; incidence has been described as up to 30-40 per 100,000. SpA symptoms are present in up to 50% of patients with inflammatory bowel disease.

Description of the registry of patients with ankylosing spondylitis in Turkey: TRASD-IP

A web-based application patient follow-up program was developed to create a registry of patients with ankylosing spondylitis (AS) by the Turkiye Romatizma Arastirma Savas Dernegi (TRASD) AS Study Group. This study describes the methodological background and patient characteristics. The patient follow-up program is a web-based questionnaire, which contains sections on socio-demographic data, anamnesis, personal and family history, systemic and musculoskeletal examination, laboratory and imaging data and treatment. Between October 1, 2007 and February 28, 2009, 1,381 patients from 41 centers were included in the registry (1,038 males [75.2%]; mean age 39.5 ± 10.7 years). Mean disease duration was 12.1 ± 8.5 years, and mean time from initial symptom to diagnosis was 5 ± 6.8 years (median 2 years). HLA-B27 positivity was detected in 73.7% of 262 patients tested. Manifestations of extraarticular involvement were anterior uveitis (13.2%), psoriasis and other skin and mucous membrane lesions (6%) and inflammatory bowel disease (3.8%). The prevalence of peripheral arthritis was 11.2%. In 51.7% of patients, the Bath AS Disease Activity Index was ≥4. But since our patients consisted of the ones with more severe disease who referred to the tertiary centers and needed a regular follow-up, they may not represent the general AS population. Disease-modifying anti-rheumatic drugs were being used by 41.9% of patients, with 16.4% using anti-TNF agents. TRASD-IP (Izlem Programi: Follow-up program) is the first AS registry in Turkey. Such databases are very useful and provide a basis for data collection from large numbers of subjects. TRASD-IP gives information on the clinical and demographic profiles of patients, and the efficacy and safety of anti-TNF drugs, examines the impact on quality of life, and provides real-life data that may be used in cost-effectiveness analyses.

Ankylosing spondylitis

Ankylosing spondylitis is a common inflammatory rheumatic disease that affects the axial skeleton, causing characteristic inflammatory back pain, which can lead to structural and functional impairments and a decrease in quality of life. New imaging techniques and therapies have substantially changed the management of this disease in the past decade. Whether inhibition of radiographic progression and structural damage can be reached with available drugs is as yet unclear. Furthermore, treatment with non-steroidal anti-inflammatory agents and physiotherapy remains an important approach to long-term management of patients with ankylosing spondylitis. The new treatment options with tumour necrosis factor blockers seems a breakthrough for patients refractory to conventional treatment.

Early diagnosis of spondyloarthritis

The term 'spondyloarthritis', which is preferred to 'spondyloarthropathy', refers to a group of similar diseases with distinct clinical features and a common genetic predisposition, rather than one disease with different clinical presentations. Mainly for clinical purposes, five disease subtypes are recognized: ankylosing spondylitis (AS), psoriatic spondyloarthritis, reactive spondyloarthritis, spondyloarthritis associated with inflammatory bowel disease, and undifferentiated spondyloarthritis. Irrespective of the disease subtype, the main clinical manifestations of spondyloarthritides are inflammatory back pain, peripheral arthritis, enthesitis and anterior uveitis, while other organ manifestations are rare. The need for a standardized, evidence-based approach to disease classification led to the development of the European Spondyloarthropathy Study Group preliminary criteria for spondyloarthritis in 1991, which confirmed the unifying concept of this group of diseases. In the past 10 years, the work of the European Spondyloarthropathy Study Group has been taken over by the Assessments in AS working group. There is still a considerable delay in diagnosis of AS and, because of the well-documented efficacy of anti-tumor-necrosis-factor therapy for all spondyloarthritis subtypes, diagnostic criteria (especially for early forms of spondyloarthritis) are needed. Diagnosis can be achieved by determination of the predominant clinical manifestation, and by the inclusion of sensitive diagnostic tools for early disease (such as HLA-B27 genotype and MRI) in the criteria set. In addition, because of the high incidence of back pain in affected individuals, the development of practical screening parameters that facilitate referral to the rheumatologist is important.

Concepts and epidemiology of spondyloarthritis

The term 'spondyloarthritides' (SpA) comprises ankylosing spondylitis (AS), reactive arthritis, arthritis/spondylitis with inflammatory bowel disease, and arthritis/spondylitis with psoriasis. The main links between these diseases are an association with HLA-B27 and a similar clinical picture. Patients normally present with chronic low back pain or asymmetrical arthritis, predominantly of the lower limbs, and an overlap of these symptoms often occurs. AS is regarded as the most severe subtype. Recent attention has focused on earlier diagnosis of AS among patients with chronic low back, and this is becoming more important as effective therapies for early treatment have become available. AS is a disease of young people, normally starting in the third decade of life. The incidence and prevalence rates of AS, and of SpA as a whole, are strongly dependent and are directly correlated to the prevalence of HLA-B27 in a given population. Incidence rates of 0.5-8.2/100 000 population and prevalence rates of 0.2-1.2% have been described for AS, and about double these figures have been reported for SpA.