Imaging to predict early relapses after treatment discontinuation in patients with large vessel giant cell arteritis - A cohort study

OBJECTIVES

To investigate the value of [18F]fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) and magnetic resonance imaging (MRI) in predicting relapse after treatment discontinuation in patients with large-vessel giant cell arteritis (LV-GCA).

METHODS

This study included patients with LV-GCA whose treatment was discontinued between 2018 and 2023. All patients underwent PET/CT and/or MRI at the time of treatment discontinuation in clinical remission. Qualitative and quantitative PET/CT scores, by measuring standardized uptake values (SUV), and semiquantitative MRI scores of the aorta and supraaortic vessels were compared between patients who relapsed within 4 months after treatment discontinuation and those who did not.

RESULTS

Forty patients were included (median age 67.4 years, interquartile range (IQR) 60.8-74.0; 77.5 % females). Eleven patients (27.5 %) relapsed after treatment discontinuation (time to relapse 1.9 months, IQR 1.4-3.3). Patients who relapsed were comparable to those who remained in remission with respect to the presence of active vasculitis on MRI and/or PET/CT (54.5% vs. 58.6 %, p = 1.0), the number of segments with vasculitic findings on MRI (0, IQR 0.0-1.5, vs. 2, IQR 0.0-3.0, p = 0.221) or the highest SUV artery/liver ratio on PET/CT (1.5, IQR 1.4-1.6, vs. 1.3, IQR 1.2-1.6, p = 0.505). The median number of vasculitic segments on PET/CT was 2.5 (IQR 0.5-4.5) in those with vs. 0 (IQR 0.0-1.5, p = 0.085) in those without relapse, and the PET/CT scores 4.5 (IQR 0.75-8.25) vs. 0 (IQR 0.0-3.0, p = 0.172).

CONCLUSION

PET/CT or MRI at treatment stop did not predict relapse and may not be suited to guide treatment decisions in patients with LV-GCA in remission.

Explainable deep learning for disease activity prediction in chronic inflammatory joint diseases

Analysing complex diseases such as chronic inflammatory joint diseases (CIJDs), where many factors influence the disease evolution over time, is a challenging task. CIJDs are rheumatic diseases that cause the immune system to attack healthy organs, mainly the joints. Different environmental, genetic and demographic factors affect disease development and progression. The Swiss Clinical Quality Management in Rheumatic Diseases (SCQM) Foundation maintains a national database of CIJDs documenting the disease management over time for 19'267 patients. We propose the Disease Activity Score Network (DAS-Net), an explainable multi-task learning model trained on patients' data with different arthritis subtypes, transforming longitudinal patient journeys into comparable representations and predicting multiple disease activity scores. First, we built a modular model composed of feed-forward neural networks, long short-term memory networks and attention layers to process the heterogeneous patient histories and predict future disease activity. Second, we investigated the utility of the model's computed patient representations (latent embeddings) to identify patients with similar disease progression. Third, we enhanced the explainability of our model by analysing the impact of different patient characteristics on disease progression and contrasted our model outcomes with medical expert knowledge. To this end, we explored multiple feature attribution methods including SHAP, attention attribution and feature weighting using case-based similarity. Our model outperforms temporal and non-temporal neural network, tree-based, and naive static baselines in predicting future disease activity scores. To identify similar patients, a k-nearest neighbours regression algorithm applied to the model's computed latent representations outperforms baseline strategies that use raw input features representation.

Plasma mtDNA as a possible contributor to and biomarker of inflammation in rheumatoid arthritis

OBJECTIVES

Neutrophil extracellular trap formation and cell-free DNA (cfDNA) contribute to the inflammation in rheumatoid arthritis (RA), but it is unknown if mitochondrial DNA (mtDNA) or nuclear DNA (nDNA) is more abundant in the circulation. It is unclear if DNA concentration measurements may assist in clinical decision-making.

METHODS

This single-center prospective observational study collected plasma from consecutive RA patients and healthy blood donors. Platelets were removed, and mtDNA and nDNA copy numbers were quantified by polymerase chain reaction (PCR).

RESULTS

One hundred six RA patients and 85 healthy controls (HC) were recruited. Circulating median mtDNA copy numbers were increased 19.4-fold in the plasma of patients with RA (median 1.1 x108 copies/mL) compared to HC (median 5.4 x106 copies/mL, p<0.0001). Receiver operating characteristics (ROC) curve analysis of mtDNA copy numbers identified RA patients with high sensitivity (92.5%) and specificity (89.4%) with an area under the curve (AUC) of 0.97, p <0.0001 and a positive likelihood ratio of 8.7. Demographic, serological (rheumatoid factor (RF) positivity, anti-citrullinated protein antibodies (ACPA) positivity) and treatment factors were not associated with DNA concentrations. mtDNA plasma concentrations, however, correlated significantly with disease activity score-28- erythrocyte sedimentation rate (DAS28-ESR) and increased numerically with increasing DAS28-ESR and clinical disease activity index (CDAI) activity. MtDNA copy numbers also discriminated RA in remission (DAS28 <2.6) from HC (p<0.0001). Also, a correlation was observed between mtDNA and the ESR (p = 0.006, R= 0.29). Similar analyses showed no significance for nDNA.

CONCLUSION

In contrast to nDNA, mtDNA is significantly elevated in the plasma of RA patients compared with HC. Regardless of RA activity, the abundance of circulating mtDNA is a sensitive discriminator between RA patients and HC. Further validation of the diagnostic value of mtDNA testing is required.

Prior polymyalgia rheumatica is associated with sonographic vasculitic changes in newly diagnosed patients with giant cell arteritis

OBJECTIVES

To investigate the hypothesis that a history of PMR is associated with a more severe and damaging disease course in newly diagnosed GCA patients.

METHODS

This was a retrospective analysis of GCA patients diagnosed between December 2006 and May 2021. We compared vascular ultrasound findings (presence of vasculitis and vascular stenosis) in GCA patients with and without prior PMR.

RESULTS

Forty-nine of 311 GCA patients (15.8%) had prior PMR in a median of 30.6 (IQR 7.1-67.3) months before GCA diagnosis. Patients with prior PMR more often had large vessel vasculitis (LVV) (51.0% vs 25.0%, P < 0.001) and stenosis within the vasculitic segments (18.4% vs 3.1%, P < 0.001) on ultrasound. In multivariable analysis, prior PMR remained significantly associated with LVV (odds ratio 7.65, 95% CI: 2.72, 23.97, P < 0.001). Polymyalgic symptoms at GCA diagnosis in the patients without prior PMR were not associated with a higher prevalence of LVV (P = 0.156).

CONCLUSION

Patients with a diagnosis of PMR before GCA diagnosis had two times more often large vessel involvement and significant more vasculitic stenoses on ultrasound examination than patients without prior PMR. Pre-existing PMR is an independent risk factor for more extensive and advanced ultrasound findings at GCA diagnosis. The contribution of subclinical vasculitis to disease associated damage should be further studied.

Minimal information for studies of extracellular vesicles (MISEV2023): From basic to advanced approaches

Extracellular vesicles (EVs), through their complex cargo, can reflect the state of their cell of origin and change the functions and phenotypes of other cells. These features indicate strong biomarker and therapeutic potential and have generated broad interest, as evidenced by the steady year-on-year increase in the numbers of scientific publications about EVs. Important advances have been made in EV metrology and in understanding and applying EV biology. However, hurdles remain to realising the potential of EVs in domains ranging from basic biology to clinical applications due to challenges in EV nomenclature, separation from non-vesicular extracellular particles, characterisation and functional studies. To address the challenges and opportunities in this rapidly evolving field, the International Society for Extracellular Vesicles (ISEV) updates its 'Minimal Information for Studies of Extracellular Vesicles', which was first published in 2014 and then in 2018 as MISEV2014 and MISEV2018, respectively. The goal of the current document, MISEV2023, is to provide researchers with an updated snapshot of available approaches and their advantages and limitations for production, separation and characterisation of EVs from multiple sources, including cell culture, body fluids and solid tissues. In addition to presenting the latest state of the art in basic principles of EV research, this document also covers advanced techniques and approaches that are currently expanding the boundaries of the field. MISEV2023 also includes new sections on EV release and uptake and a brief discussion of in vivo approaches to study EVs. Compiling feedback from ISEV expert task forces and more than 1000 researchers, this document conveys the current state of EV research to facilitate robust scientific discoveries and move the field forward even more rapidly.

Early axial spondyloarthritis according to the ASAS consensus definition: characterisation of patients and effectiveness of a first TNF inhibitor in a large observational registry

OBJECTIVE

To characterise the population fulfilling the Assessment of SpondyloArthritis international Society (ASAS) consensus definition of early axial spondyloarthritis (axSpA) and to determine the effectiveness of a first tumour necrosis factor inhibitor (TNFi) in early versus established axSpA in a large observational registry.

METHODS

A total of 3064 patients with axSpA in the Swiss Clinical Quality Management registry with data on duration of axial symptoms were included (≤2 years=early axSpA, N=658; >2 years=established axSpA, N=2406). Drug retention was analysed in patients starting a first TNFi in early axSpA (N=250) versus established axSpA (N=874) with multiple-adjusted Cox proportional hazards models. Adjusted logistic regression analyses were used to determine the achievement of the ASAS criteria for 40% improvement (ASAS40) at 1 year.

RESULTS

Sex distribution, disease activity, impairments of function and health-related quality of life were comparable between patients with early and established axSpA. Patients with established disease were older, had more prevalent axial radiographical damage and had a higher impairment of mobility. A comparable TNFi retention was found in early versus established disease after adjustment for age, sex, human leucocyte antigen-B27 status, education, body mass index, smoking, elevated C reactive protein and sacroiliac inflammation on MRI (HR 1.05, 95% CI 0.78 to 1.42). The adjusted ASAS40 response was similar in the two groups (OR 1.09, 95% CI 0.67 to 1.78). Results were confirmed in the population fulfilling the ASAS classification criteria.

CONCLUSION

Considering the recent ASAS definition of early axSpA, TNFi effectiveness seems comparable in early versus established disease.

Serious infection risk of tofacitinib compared to biologics in patients with rheumatoid arthritis treated in routine clinical care

Recently, serious infections related to the use of tofacitinib (TOF) for treatment of rheumatoid arthritis (RA) have raised considerable interest. This study aimed to compare the risk for serious infections in patients with RA upon receiving TOF versus biologic disease-modifying antirheumatic drugs (bDMARDs) by age at treatment initiation. We identified adult RA patients exposed to TOF or bDMARDs using data collected by the Swiss registry for inflammatory rheumatic diseases (SCQM) from 2015 to 2018. The event of interest was the first non-fatal serious infection (SI) during drug exposure. Missing or incomplete SI dates were imputed as either the lower (left) or upper (right) limit of the known occurrence interval. The ratio of SI hazards (HR) of TOF versus bDMARDs was estimated as a function of age using covariate-adjusted Cox regression applied to each type of imputed time-to-SI. A total of 1687 patients provided time at risk for a first SI during study participation and drug exposure for 2238 different treatment courses, 345 for TOF and 1893 for bDMARDs. We identified 44 (left imputation) or 43 (right imputation), respectively, first SIs (12/12 on TOF versus 32/31 on bDMARDs). Left and right imputation produced similar results. For patients aged ≥ 69 years, the treatment HR started to be increased (lower limit of 95% confidence intervals (LLCIs) > 1). By the age of 76, the difference between TOF and bDMARDs started to be clinically relevant (LLCIs > 1.25). For patients aged < 65 years, the data were insufficient to draw conclusions. Our results suggest that we should expect an increased risk for SIs in older patients treated with TOF compared to bDMARDs supporting a cautious use of TOF in these patients.

Anaemia is associated with higher disease activity in axial spondyloarthritis but is not an independent predictor of spinal radiographic progression: data from the Swiss Clinical Quality Management Registry

OBJECTIVE

As anaemia represents a biomarker for increased radiographic damage in rheumatoid arthritis, we aimed to investigate whether it independently predicts spinal radiographic progression in axial spondyloarthritis (axSpA).

METHODS

AxSpA patients with available haemoglobin levels from the prospective Swiss Clinical Quality Management Registry were included for comparison of patients with and without anaemia. Spinal radiographic progression was assessed according to the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) in patients with ankylosing spondylitis (AS) if ≥ 2 sets of spinal radiographs were available every 2 years. The relationship between anaemia and progression (defined as an increase ≥ 2 mSASSS units in 2 years) was analysed with generalized estimating equation models after adjustment for the Ankylosing Spondylitis Disease Activity Score (ASDAS) and potential confounding, as well as after multiple imputations of missing values.

RESULTS

A total of 212/2522 axSpA patients presented with anaemia (9%). Anaemic patients had higher clinical disease activity, higher acute phase reactants and more severe impairments in physical function, mobility and quality of life. In the subgroup of patients with AS (N = 433), a comparable mSASSS progression was found in anaemic and non-anaemic patients (OR 0.69, 95% CI 0.25 to 1.96, p = 0.49). Age, male sex, baseline radiographic damage and ASDAS were associated with enhanced progression. The results were confirmed in complete case analyses and with progression defined as the formation of ≥ 1 syndesmophyte in 2 years.

CONCLUSION

Although anaemia was associated with higher disease activity in axSpA, it did not additionally contribute to the prediction of spinal radiographic progression. Key Points • Anaemia is associated with higher disease activity and more severely impaired physical function, mobility and quality of life in axSpA. • Anaemia does not provide an additional value to ASDAS for prediction of spinal radiographic progression.

Obesity Represents a Persisting Health Issue in Axial Spondyloarthritis, Particularly Affecting Socially Disadvantaged Patients

OBJECTIVE

Obesity is an important comorbidity in axial spondyloarthritis (axSpA); however, the prevalence of obesity in axSpA compared with the general population and associated socioeconomic factors remain unknown.

METHODS

This repeated cross-sectional study compared BMI (kg/m2) groups of patients with axSpA to the Swiss population at 3 timepoints (2007, 2012, and 2017). BMI categories were compared by different age, sex, and education categories using the chi-square goodness of fit test. Unpaired, 1-sided t tests were used to compare the BMI in patients with axSpA between the different timepoints.

RESULTS

Compared to the general population, patients with axSpA had a higher proportion of overweight and obesity: 18.9% of all patients with axSpA were obese, compared to 11.3% of the Swiss population in 2017. Comparison of BMI groups within sex, age, and education groups consistently showed a trend toward higher rates of overweight and obesity in axSpA. Further, patients with axSpA, especially females, showed a trend of increasing BMI over the studied 10 years. At every time point, overweight and obese patients were significantly more likely to be male, were older, and had higher disease activity than patients with normal weight. Obesity was associated with a deprived socioeconomic status as indicated by a higher proportion of patients with manual labor jobs and lower levels of education.

CONCLUSION

The prevalence of obesity was significantly higher among patients with axSpA compared to the Swiss population, with socially disadvantaged individuals being the most affected. There is an urgent need to initiate prevention strategies for obesity in patients with axSpA.

Rapid glucocorticoid tapering regimen in patients with giant cell arteritis: a single centre cohort study

OBJECTIVES

We evaluated the feasibility of a rapid glucocorticoid tapering regimen to reduce glucocorticoid exposure in patients with giant cell arteritis (GCA) treated with glucocorticoids only.

METHODS

Newly diagnosed patients with GCA treated with a planned 26-week glucocorticoid tapering regimen at the University Hospital Basel were included. Data on relapses, cumulative steroid doses (CSD) and therapy-related adverse effects were collected from patients' records.

RESULTS

Of 47 patients (64% women, median age 72 years), 32 patients (68%) had relapsed. Most relapses were minor (28/32) and 2/3 of those were isolated increased inflammatory markers (19/32). Among major relapses, one resulted in permanent vision loss. The median time until relapse was 99 days (IQR 71-127) and median glucocorticoid dose at relapse was 8 mg (IQR 5-16). Nine of 47 patients stopped glucocorticoids after a median duration of 35 weeks and did not relapse within 1 year. Median CSD at 12 months was 4164 mg which is lower compared with published data. Glucocorticoid-associated adverse effects occurred in 40% of patients, most frequently were new onset or worsening hypertension (19%), diabetes (11%) and severe infections (11%).

CONCLUSION

We could demonstrate that 32% of patients remained relapse-free and 19% off glucocorticoids at 1 year after treatment with a rapid glucocorticoid tapering regimen. Most relapses were minor and could be handled with temporarily increased glucocorticoid doses. Consequently, the CSD at 12 months was much lower than reported in published cohorts. Thus, further reducing treatment-associated damage in patients with GCA by decreasing CSD seems to be possible.

Preclinical characterization of the Toll-like receptor 7/8 antagonist MHV370 for lupus therapy

Genetic and in vivo evidence suggests that aberrant recognition of RNA-containing autoantigens by Toll-like receptors (TLRs) 7 and 8 drives autoimmune diseases. Here we report on the preclinical characterization of MHV370, a selective oral TLR7/8 inhibitor. In vitro, MHV370 inhibits TLR7/8-dependent production of cytokines in human and mouse cells, notably interferon-α, a clinically validated driver of autoimmune diseases. Moreover, MHV370 abrogates B cell, plasmacytoid dendritic cell, monocyte, and neutrophil responses downstream of TLR7/8. In vivo, prophylactic or therapeutic administration of MHV370 blocks secretion of TLR7 responses, including cytokine secretion, B cell activation, and gene expression of, e.g., interferon-stimulated genes. In the NZB/W F1 mouse model of lupus, MHV370 halts disease. Unlike hydroxychloroquine, MHV370 potently blocks interferon responses triggered by specific immune complexes from systemic lupus erythematosus patient sera, suggesting differentiation from clinical standard of care. These data support advancement of MHV370 to an ongoing phase 2 clinical trial.

HLA-B27 as a predictor of effectiveness of treatment with TNF inhibitors in axial spondyloarthritis: data from the Swiss Clinical Quality Management Registry

OBJECTIVE

To explore the impact of the human leucocyte antigen (HLA)-B27 on the effectiveness of tumor necrosis factor inhibitors (TNFi) in patients with axial spondyloarthritis (axSpA).

METHODS

A total of 1109 patients with available HLA-B27 status (831 B27+ patients and 278 B27- patients) fulfilling the Assessment of Spondyloarthritis international Society classification criteria for axSpA from the prospective Swiss Clinical Quality Management Registry initiating a first TNFi were included. Drug retention was investigated with multiple adjusted Cox proportional hazard models with imputation of missing values. Multiple-adjusted logistic regression analyses were used to assess the proportion of patients reaching 50% reduction in the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI50) at 1 year.

RESULTS

B27+ and B27- patients differed with regard to age, sex, BASDAI, C-reactive protein (CRP), body mass index, enthesitis, uveitis, and classification status. After adjustment for potential confounders for the relationship between HLA-B27 and drug effectiveness (sex and family history of spondyloarthritis), a higher risk of drug discontinuation was found in B27- patients (HR 1.53, 95% CI 1.27-1.83). This difference decreased after additional adjustment for parameters which may act as mediators (HR 1.30, 95% CI 1.30-1.55). Male sex and elevated C-reactive protein (CRP) levels were consistently associated with longer retention. Comparable results were obtained for BASDAI50 responses.

CONCLUSION

The HLA-B27 genotype is an important predictor of treatment effectiveness. Male sex and CRP seem, however, to better describe variability of response in individual patients. This data may help avoiding potential discrimination of B27- individuals with regard to TNFi initiation. Key Points • HLA-B27 is a predictor of effectiveness of TNF inhibitors in axial spondyloarthritis. • Variability of response in individual patients is better defined by sex and objective markers of disease activity, such as C-reactive protein.

Mitochondrial DNA: a novel indicator of active inflammation in ANCA-associated vasculitides

OBJECTIVES

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) includes granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA). ANCA triggers neutrophil extracellular trap formation, which releases either mitochondrial (mt) DNA or nuclear DNA (n) DNA, contributing to inflammation. Our aim was to prospectively examine the extent and nature of circulating DNA in AAV and the clinical utility of DNA quantification.

METHODS

DNA was isolated from platelet-free plasma of consecutive GPA and MPA patients and healthy controls (HC). mtDNA and nDNA copy numbers were quantified by PCR. Clinical data including the Birmingham Vasculitis Activity Score (BVAS), were collected.

RESULTS

Ninety-two HC (median age 51 years, 58.7% female) and 101 AAV patients (80 GPA, 21 MPA, median age 64 years, 50.5% female, BVAS range: 0-30) were included. Median mtDNA copies were 13-fold higher in AAV than HC; nDNA concentrations did not differ. Patients with active AAV (BVAS > 0) had 4-fold higher median mtDNA copies than patients in remission (P= 0.03). mtDNA, unlike nDNA, correlated with BVAS (r = 0.30, P= 0.002) and was associated with AAV activity at multivariable analysis. Receiver operating characteristic curve analysis indicates that mtDNA quantification differentiates active AAV (BVAS >0) from HC with 96.1% sensitivity and 98.9% specificity (AUC 0.99). In 27 AAV patients with follow-up, mtDNA changes but not CRP or ANCA-titers correlated with BVAS changes (r = 0.56, P= 0.002).

CONCLUSIONS

mtDNA, unlike nDNA, is elevated in the plasma of AAV patients and may contribute to systemic inflammation. mtDNA could be superior to established biomarkers in the laboratory monitoring of AAV activity.

Long delay from symptom onset to first consultation contributes to permanent vision loss in patients with giant cell arteritis: a cohort study

OBJECTIVES

To characterise factors associated with permanent vision loss (PVL) and potential reasons for the therapeutic delay contributing to PVL in giant cell arteritis (GCA).

METHODS

Retrospective analysis of GCA patients diagnosed at the University Hospital Basel between December 2006 and May 2021.

RESULTS

Of 282 patients with GCA (64% females), 49 (17.4%) experienced PVL. In 43/49 (87.8%) PVL occurred before treatment. Of these, 24 (55.8%) patients had first non-ocular symptoms and eventually sought consultation when PVL occurred in a median of 21 (IQR 14.75-31.0) days after the first symptoms. Only five of the 24 patients had consulted a physician before PVL, but GCA diagnosis was missed. Treatment was initiated rapidly after diagnosis (median 1 day (IQR 0.0-7.0)). PVL on therapy occurred in six patients in a median of 40 (IQR 20.5-67.3) days after treatment started. In two of those, glucocorticoids were tapered too quickly.In multivariable analysis, patients with PVL were older (OR 1.17, 95% CI 1.07 to 1.29, p=0.001) and reported more frequently jaw claudication (OR 3.52, 95% CI 1.02 to 13.16, p=0.051). PVL was present in 18 (42.9%) of the 42 patients with vasculitic ultrasound findings in all six temporal artery segments. The incidence of PVL over 15 years did not decline (Spearman rank=0.3, p=0.68).

CONCLUSION

The prevalence of GCA-associated PVL remains high. Associated factors were advanced age, jaw claudication and ultrasound findings consistent with vasculitis in all six temporal artery segments. Despite preceding non-ocular GCA symptoms weeks before the onset of PVL, most patients were not seen by a rheumatologist before PVL occurred.

Comparison of drug retention of TNF inhibitors, other biologics and JAK inhibitors in RA patients who discontinued JAK inhibitor therapy

OBJECTIVES

JAK Inhibitors (JAKi) are recommended DMARDs for patients with moderate-to-severe RA who failed first-line therapy with methotrexate. There is a lack of data allowing an evidence-based choice of subsequent DMARD therapy for patients who had discontinued JAKi treatment. We aimed to compare the effectiveness of TNF inhibitor (TNFi) therapy vs JAKi vs other mode of action (OMA) biologic DMARD (bDMARD) in RA patients who were previously treated with a JAKi.

METHODS

RA patients who discontinued JAKi treatment within the Swiss RA registry SCQM were included for this observational prospective cohort study. The primary outcome was drug retention for either TNFi, OMA bDMARD or JAKi. The hazard ratio for treatment discontinuation was calculated adjusting for potential confounders. A descriptive analysis of the reasons for discontinuation was performed.

RESULTS

Four hundred treatment courses of JAKi were included, with a subsequent switch to either JAKi, TNFi or OMA bDMARD. The crude overall drug retention was higher in patients switching to another JAKi as compared with TNFi and comparable to OMA. A significant difference of JAKi vs TNFi persisted after adjusting for potential confounders.

CONCLUSION

In a real-world population of RA patients who discontinued treatment with a JAKi, switching to another JAKi resulted in a higher drug retention than switching to a TNFi. A switch to a second JAKi seems an effective therapeutic option.

The role of C5a-C5aR1 axis in bone pathophysiology: A mini-review

Bone remodeling is a physiological, dynamic process that mainly depends on the functions of 2 cell types: osteoblasts and osteoclasts. Emerging evidence suggests that complement system is crucially involved in the regulation of functions of these cells, especially during inflammatory states. In this context, complement component 5a (C5a), a powerful pro-inflammatory anaphylatoxin that binds the receptor C5aR1, is known to regulate osteoclast formation and osteoblast inflammatory responses, and has thus been proposed as potential therapeutic target for the treatment of inflammatory bone diseases. In this review, we will analyze the role of C5a-C5aR1 axis in bone physiology and pathophysiology, describing its involvement in the pathogenesis of some of the most frequent inflammatory bone diseases such as rheumatoid arthritis, and also in osteoporosis and bone cancer and metastasis. Moreover, we will examine C5aR1-based pharmacological approaches that are available and have been tested so far for the treatment of these conditions. Given the growing interest of the scientific community on osteoimmunology, and the scarcity of data regarding the role of C5a-C5aR1 axis in bone pathophysiology, we will highlight the importance of this axis in mediating the interactions between skeletal and immune systems and its potential use as a therapeutic target.

Nonhematopoietic IRAK1 drives arthritis via neutrophil chemoattractants

IL-1 receptor-activated kinase 1 (IRAK1) is involved in signal transduction downstream of many TLRs and the IL-1R. Its potential as a drug target for chronic inflammatory diseases is underappreciated. To study its functional role in joint inflammation, we generated a mouse model expressing a functionally inactive IRAK1 (IRAK1 kinase deficient, IRAK1KD), which also displayed reduced IRAK1 protein expression and cell type–specific deficiencies of TLR signaling. The serum transfer model of arthritis revealed a potentially novel role of IRAK1 for disease development and neutrophil chemoattraction exclusively via its activity in nonhematopoietic cells. Consistently, IRAK1KD synovial fibroblasts showed reduced secretion of neutrophil chemoattractant chemokines following stimulation with IL-1β or human synovial fluids from patients with rheumatoid arthritis (RA) and gout. Together with patients with RA showing prominent IRAK1 expression in fibroblasts of the synovial lining, these data suggest that targeting IRAK1 may be therapeutically beneficial. As pharmacological inhibition of IRAK1 kinase activity had only mild effects on synovial fibroblasts from mice and patients with RA, targeted degradation of IRAK1 may be the preferred pharmacologic modality. Collectively, these data position IRAK1 as a central regulator of the IL-1β–dependent local inflammatory milieu of the joints and a potential therapeutic target for inflammatory arthritis.

IgA rheumatoid factor in rheumatoid arthritis

OBJECTIVES

Rheumatoid factor (RF) is a well-established marker for the diagnosis and classification of rheumatoid arthritis (RA). Most studies evaluated IgM RF or isotype-nonspecific total RF assays. We evaluated the added value of IgA RF in this context.

METHODS

An international sample cohort consisting of samples from 398 RA patients and 1073 controls was tested for IgA RF with 3 commercial assays. For all RA patients and 100 controls essential clinical and serological data for ACR/EULAR classification were available.

RESULTS

The sensitivity of IgA RF for diagnosing RA was lower than the sensitivity of IgM RF. Differences in numerical values between IgA RF assays were observed. With all assays, the highest IgA RF values were found in patients with primary Sjögren's syndrome. Double positivity for IgM RF and IgA RF had a higher specificity for RA than either IgM RF or IgA RF. The sensitivity of double positivity was lower than the sensitivity of either IgA RF or IgM RF. Single positivity for IgA RF was at least as prevalent in controls than in RA patients. Adding IgA RF to IgM RF and anti-citrullinated protein antibodies (ACPA) did not affect RA classification. However, combined positivity for IgA RF, IgM RF and IgG ACPA had a higher specificity and lower sensitivity for RA classification than positivity for either of the antibodies.

CONCLUSIONS

IgA RF showed a lower sensitivity than IgM RF. Combining IgA RF with IgM RF and ACPA did not improve sensitivity of RA classification. Combined positivity (IgA-RF/IgM-RF/ACPA) increased specificity.

Skeletal Muscle Disorders: A Noncardiac Source of Cardiac Troponin T

BACKGROUND

Cardiac troponin (cTn) T and cTnI are considered cardiac specific and equivalent in the diagnosis of acute myocardial infarction. Previous studies suggested rare skeletal myopathies as a noncardiac source of cTnT. We aimed to confirm the reliability/cardiac specificity of cTnT in patients with various skeletal muscle disorders (SMDs).

METHODS

We prospectively enrolled patients presenting with muscular complaints (≥2 weeks) for elective evaluation in 4 hospitals in 2 countries. After a cardiac workup, patients were adjudicated into 3 predefined cardiac disease categories. Concentrations of cTnT/I and resulting cTnT/I mismatches were assessed with high-sensitivity (hs-) cTnT (hs-cTnT-Elecsys) and 3 hs-cTnI assays (hs-cTnI-Architect, hs-cTnI-Access, hs-cTnI-Vista) and compared with those of control subjects without SMD presenting with adjudicated noncardiac chest pain to the emergency department (n=3508; mean age, 55 years; 37% female). In patients with available skeletal muscle biopsies, TNNT/I1-3 mRNA differential gene expression was compared with biopsies obtained in control subjects without SMD.

RESULTS

Among 211 patients (mean age, 57 years; 42% female), 108 (51%) were adjudicated to having no cardiac disease, 44 (21%) to having mild disease, and 59 (28%) to having severe cardiac disease. hs-cTnT/I concentrations significantly increased from patients with no to those with mild and severe cardiac disease for all assays (all P<0.001). hs-cTnT-Elecsys concentrations were significantly higher in patients with SMD versus control subjects (median, 16 ng/L [interquartile range (IQR), 7-32.5 ng/L] versus 5 ng/L [IQR, 3-9 ng/L]; P<0.001), whereas hs-cTnI concentrations were mostly similar (hs-cTnI-Architect, 2.5 ng/L [IQR, 1.2-6.2 ng/L] versus 2.9 ng/L [IQR, 1.8-5.0 ng/L]; hs-cTnI-Access, 3.3 ng/L [IQR, 2.4-6.1 ng/L] versus 2.7 ng/L [IQR, 1.6-5.0 ng/L]; and hs-cTnI-Vista, 7.4 ng/L [IQR, 5.2-13.4 ng/L] versus 7.5 ng/L [IQR, 6-10 ng/L]). hs-cTnT-Elecsys concentrations were above the upper limit of normal in 55% of patients with SMD versus 13% of control subjects (P<0.01). mRNA analyses in skeletal muscle biopsies (n=33), mostly (n=24) from individuals with noninflammatory myopathy and myositis, showed 8-fold upregulation of TNNT2, encoding cTnT (but none for TNNI3, encoding cTnI) versus control subjects (n=16, P_Wald<0.001); the expression correlated with pathological disease activity (R=0.59, P_t-statistic<0.001) and circulating hs-cTnT concentrations (R=0.26, P_t-statistic=0.031).

CONCLUSIONS

In patients with active chronic SMD, elevations in cTnT concentrations are common and not attributable to cardiac disease in the majority. This was not observed for cTnI and may be explained in part by re-expression of cTnT in skeletal muscle.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT03660969.

Standardisation of ACPA tests: evaluation of a new candidate reference preparation

INTRODUCTION

Commercial assays measuring antibodies to citrullinated protein/peptide (ACPA) show poor quantitative agreement. The diagnostic industry has never adopted the International Union of Immunological Societies-Centers for Disease Control and Prevention (IUIS-CDC) ACPA reference standard. Recently, the National Institute for Biological Standards and Control (NIBSC) prepared a new candidate ACPA standard (18/204). We evaluated both reference materials using different commercially available ACPA assays.

MATERIALS AND METHODS

This is an international study in which the NIBSC candidate ACPA standard and the IUIS-CDC ACPA reference material were analysed together with 398 diagnostic samples from individuals with rheumatoid arthritis (RA) and in 1073 individuals who did not have RA using nine commercial ACPA assays.

RESULTS

For both reference materials and samples from individuals with RA and individuals who did not have RA, there were large differences in quantitative ACPA results between assays. For most assays, values for the IUIS-CDC standard were lower than values for NIBSC 18/204 and the IUIS-CDC/NIBSC ratio was comparable for several, but not all assays. When NIBSC 18/204 was used as a calibrator, an improvement in alignment of ACPA results across several of the evaluated assays was obtained. Moreover, NIBSC 18/204 could align clinical interpretation for some but not all assays.

CONCLUSION

Adoption of an international standard for ACPA determination is highly desirable. The candidate NIBSC 18/204 standard improved the standardisation and alignment of most ACPA assays and might therefore be recommended to be used as reference in commercial assays.

POS0536 REFINING THE SEROLOGICAL SCORES OF THE ACR/EULAR 2010 RHEUMATOID ARTHRITIS CLASSIFICATION CRITERIA: AN INTERNATIONAL STUDY

Background

Rheumatoid factor (RF) and anti-cyclic citrullinated protein/peptide antibodies (ACPA) are included in the ACR/EULAR 2010 classification criteria for rheumatoid arthritis (RA)(1). Both markers are given the same weight in the criteria.

Objectives

As the performance characteristics differ significantly between RF and ACPA(2), we set out to refine the serological scores for RA classification.

Methods

Diagnostic samples from 398 RA patients and from 1073 diseased controls were evaluated with five RF assays (two RF IgM isotype-specific assays and three total RF assays) and five ACPA IgG assays from five different manufacturers.

Results

Firstly, we harmonized thresholds between manufacturers based on predefined specificity for low positive (at 92.5% specificity for RF and at 97.5% specificity ACPA) and high positive results (at 97.5% specificity RF and at 99.0% specificity for ACPA). Next, we determined likelihood ratios (LRs) for RF, ACPA, and combinations of both, for negative, low positive, and high positive results. The LR was higher for ACPA than for RF, for high positive results than for low positive results and for double positivity than for single positivity. Based on these data we refined the weights of serological scores for classification (Table 1).

Table 1.

Refined weights of serological scores for RA classification

RF negativeRF low positiveRF high positiveACPA negative011ACPA low positive233ACPA high positive344

Application of such refined serological weights significantly increased the area under the curve of receiver operating characteristics analysis to distinguish RA from controls, significantly reduced the serological scores in the controls as well as the number of RA misclassifications without affecting the diagnostic sensitivity.

Besides, we showed that combining predefined specificity thresholds with the refined serological scoring, reduced manufacturer-dependent variability in RA classification impacting RA classification for controls from 18.0-29.0% by ACR/EULAR to 11.0-13.0% (significantly increasing specificity) and for RA patients from 67.8-74.0% to 67.6-71.5% (without significantly affecting sensitivity).

Conclusion

Serological weight factors for RA classification can be improved by taking into account the antibody type (RF versus ACPA), the antibody level, and single or combined positivity.

References

[1]Aletaha D, Neogi T, Silman AJ, Funovits J, Felson DT, Bingham COr, et al. 2010 rheumatoid arthritis classification criteria: an American College of Rheumatology/European League Against Rheumatism collaborative initiative. Ann Rheum Dis 2010; 69: 1580-8.

[2]Bossuyt X. Anticitrullinated protein antibodies: taking into account antibody levels improves interpretation. Ann Rheum Dis 2017; 76: e33.

Acknowledgements

We thank all participating diagnostic companies for the in-kind support of assays, their technical training and the constructive discussions. Furthermore, we are very thankful to the laboratory technicians of all participating laboratories for their most appreciated assistance in the performance of the RF/ACPA analyses.

Disclosure of Interests

Lieve Van Hoovels Speakers bureau: Thermo Fisher, Consultant of: Thermo Fisher, Grant/research support from: Thermo Fisher, Bert Vander Cruyssen: None declared, Daniela Sieghart Speakers bureau: Thermo Fisher, Consultant of: Thermo Fisher, Carolien Bonroy: None declared, Eszter Nagy: None declared, Rille Pullerits: None declared, Saša Čučnik: None declared, Charlotte Dahle: None declared, Ingmar Heijnen Speakers bureau: Thermo Fisher, Luca Bernasconi Speakers bureau: Thermo Fisher, Farid Benkhadra: None declared, Laura Bogaert: None declared, Stefanie Van Den Bremt: None declared, Ann Vanliedekerke: None declared, Geert Vanheule: None declared, Johan Robbrecht: None declared, Lucy Studholme: None declared, Wirth Claudine: None declared, Rüdiger Müller: None declared, Diego Kyburz: None declared, Christopher Sjowall: None declared, Alf Kastbom: None declared, Rok Jese: None declared, Boja Jovancevic: None declared, Emese Virag Kiss: None declared, Peggy Jacques: None declared, Günter Steiner Speakers bureau: Thermo Fisher, Consultant of: Thermo Fisher, Patrick Verschueren: None declared, Xavier Bossuyt Speakers bureau: Thermo Fisher, Consultant of: Thermo Fisher.

POS0250 PLASMA MITOCHONDRIAL DNA AS A BIOMARKER IN THE DIAGNOSIS AND FOLLOW-UP OF ANCA-ASSOCIATED VASCULITIDES

Background

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV) include granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA) (1, 2). ANCA recognize the antimicrobial proteins proteinase 3 (PR3) or myeloperoxidase (MPO) (1,2) and trigger the formation of neutrophil extracellular traps (NETs), which release DNA into the extracellular space and systemic circulation. This cell-free (cf)DNA induces endothelial damage, vascular inflammation and necrosis (3).

Objectives

The nature, diagnostic and prognostic value of cfDNA in AAV is still unknown. The aim of the present study was to examine the clinical utility of cfDNA quantification as a biomarker in AAV.

Methods

Total DNA was isolated from platelet-free plasma samples of healthy controls (HC) and consecutive AAV patients. Plasma and clinical data were collected at baseline and follow-up. Copy numbers were quantified by qPCR for mtDNA (ATP-6 gene) and nuclear (n) DNA (GAPDH gene) (4). Patients with eosinophilic GPA (EGPA) were excluded.

Results

Ninety-two HC (median age 51 ± 9, 48.2% female) and 104 AAV patients (median age 64 ± 10, 48% female, mean BVAS: 0; range: 0-40) were available for analysis. Eighty-four (80.8%) of these patients were diagnosed with GPA, and 20 with MPA (19.2%).

mtDNA levels were significantly elevated in AAV plasma (8.7x107 copies/ml plasma, 95% CI: 5.3x107 to 1.3 x108)), compared to HC plasma (6.7x106 copies/ml plasma, 95% CI: 5.4x106 to 9.1x107, p<0.0001). nDNA levels in contrast did not differ between AAV (4.0x106 copies/ml plasma, 95%CI: 2.7x106 to 5.0x106) and HC (3.3x106 copies/ml plasma, 95%CI: 2.4x106 to 4.7x106, p=0.30). ROC analysis showed that a cut-off value of 1.3x107 mtDNA copy numbers differentiated between AAV and HC with 89.4% sensitivity, 82.6% specificity and an AUC of 0.94. For AAV patients with active AAV, a cut-off value of 2.9x107 mtDNA copy numbers differentiated between AAV and HC with 96.1% sensitivity, 98.9% specificity and an AUC of 0.99 (Figure 1a).

Figure 1.

(a.) ROC curve for mtDNA plasma concentrations to discriminate between HC and active AAV patients (BVAS>0). AUC: area under the curve. (b.) Plasma mtDNA levels distinguish between AAV patients with active disease versus patients in a state of remission. Whiskers represent 95% CI. (c.) Plasma mtDNA levels in AAV patients correlate with the evolution of disease activity at follow-up.

With the exception of the peripheral nervous system involvement, there was no association of mtDNA elevation with any particular type of active organ involvement at the time of blood sampling. A positive correlation between all cell-free DNA species and anti-MPO antibody titres was observed, as expected (for cfDNA, nDNA and mtDNA - r=0.25, p=0.01; r=0.21, p=0.02; r=0.22, p=0.02, respectively).

AAV patients with active disease (BVAS>0) had a mean of 2.0x108 copies/ml of mtDNA in plasma which was higher compared to HC (p<0.0001) and AAV patients in remission (BVAS=0) (6.2x107copies/ml, p=0.03). For nDNA on the other hand, there were similar levels in active disease as in remission (5.3x106 and 4.8x106 copies/ml, respectively; p=0.64) (Figure 1b).

Follow-up data were available for 27 AAV patients (median follow-up: 6 ± 6 months, IQR: 12). Longitudinal changes in mtDNA levels robustly correlated with changes in BVAS (r=0.56, p=0.002, Figure 1c).

Conclusion

The quantification of cell free mtDNA - but not nDNA - copy numbers allows a sensitive and specific distinction between healthy individuals and patients with active AAV. mtDNA levels correlate cross sectionally with disease activity in AAV patients. Plasma mtDNA quantification may therefore aid in the diagnosis of AAV and in monitoring AAV activity.

References

[1]Kitching, A.R., et al. Nat Rev Dis Primers6, 71 (2020).

[2]Kallenberg, C. Nat Rev Rheumatol10, 484–493 (2014).

[3]Kessenbrock, K., et al. Nat Med15, 623–625 (2009).

[4]Giaglis S, et al. RMD Open 2021;7:e002010.(2021)

Disclosure of Interests

None declared

Multicentre study to improve clinical interpretation of rheumatoid factor and anti-citrullinated protein/peptide antibodies test results

BACKGROUND

Rheumatoid factor (RF) and anti-citrullinated protein/peptide antibodies (ACPA) are important biomarkers for diagnosis of rheumatoid arthritis (RA). However, there is poor harmonisation of RF and ACPA assays. The aim of this study was to refine RF and ACPA interpretation across commercial assays.

MATERIALS AND METHODS

Six total RF isotype-non-specific assays, 3 RF IgM isotype-specific assays and 9 ACPA immunoglobulin G assays of 13 different companies were evaluated using 398 diagnostic samples from patients with RA and 1073 disease controls.

RESULTS

Using cut-offs proposed by the manufacturer, there was a large variability in diagnostic sensitivity and specificity between assays. Thresholds of antibody levels were determined based on predefined specificities and used to define test result intervals. Test result interval-specific likelihood ratios (LRs) were concordant across the different RF and ACPA assays. For all assays, the LR for RA increased with increasing antibody level. Higher LRs were found for ACPA than for RF. ACPA levels associated with LRs >80 were found in a substantial fraction (>22%) of patients with RA.

CONCLUSION

Defining thresholds for antibody levels and assigning test result interval-specific LRs allows alignment of clinical interpretation for all RF and ACPA assays.

Current differentiation between radiographic and non-radiographic axial spondyloarthritis is of limited benefit for prediction of important clinical outcomes: data from a large, prospective, observational cohort

OBJECTIVE

To compare disease characteristics and outcomes between patients with axial spondyloarthritis with non-radiographic disease (nr-axSpA), bilateral grade 2 sacroiliitis (r22axSpA) and unilateral/bilateral grade 3-4 sacroiliitis (r3+axSpA) according to the modified New York criteria.

METHODS

We included patients with axial spondyloarthritis with available pelvic radiographs from the Swiss Clinical Quality Management Cohort. Retention of a first tumour necrosis factor inhibitor (TNFi) was investigated with multiple adjusted Cox proportional hazards models. The proportion of patients reaching 50% reduction in the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI50) at 1 year was assessed with multiple adjusted logistic regression analyses. Spinal radiographic progression, defined as an increase in ≥2 mSASSS units in 2 years, was assessed in generalised estimating equation models.

RESULTS

From 2080 patients, those with nr-axSpA (n=485) and r22axSpA (n=443) presented with lower C reactive protein levels and less severe clinical spinal involvement compared with patients with r3+axSpA (n=1152). While TNFi retention was similar in r22axSpA and nr-axSpA, the risk of discontinuation was significantly lower in r3+axSpA (HR 0.60, 95% CI 0.44 to 0.82 vs nr-axSpA). BASDAI50 responses at 1 year were comparable in r22axSpA and nr-axSpA, with a better response associated with r3+axSpA (OR 2.05, 95% CI 1.09 to 3.91 vs nr-axSpA). Spinal radiographic progression was similar in r22axSpA and nr-axSpA and significantly higher in r3 +axSpA.

CONCLUSION

Patients with r22axSpA are comparable to nr-axSpA patients but differ from patients with more severe sacroiliac damage with regard to treatment effectiveness and spinal radiographic progression. Therefore, current differentiation between nr-axSpA and radiographic disease seems of limited use for outcome prediction.