Evaluation of concomitant peripheral arthritis in patients with recent onset axial spondyloarthritis: 5-year results from the DESIR cohort

Real-World Adherence and Drug Survival of Biologics among Patients with Ankylosing Spondylitis

Objectives: The objective of this study was to evaluate the real-world drug survival, adherence, and discontinuation risk of biologics disease-modifying anti-rheumatic drugs (bDMARDs) among patients with ankylosing spondylitis (AS). Methods: This was a retrospective study using a computerized database. Biologic-naïve and biologic-experienced AS patients who initiated treatment with bDMARDs (tumor necrosis factor alpha inhibitors {TNF-αis} or interleukin-17 inhibitor {IL-17i}) during 2015-2018 were included. Adherence was assessed using the proportion of days covered (PDC) method. Drug survival was analyzed using Kaplan-Meier estimates. Risk of discontinuation was estimated by the Cox proportional hazard model. Results: We identified 343 eligible patients utilizing 481 lines of therapy. The mean age was 44.6 years (SD ± 13.4), 57.7% were males, and 69.7% were biologic-naïve at baseline. The proportion of highly adherent patients (PDC ≥ 0.8) in the biologic-naïve group was 63.5% for golimumab, 69.2% for etanercept, and 71.6% for adalimumab (p > 0.9). Among the biologic-experienced group, secukinumab had the highest proportion of adherent patients (75.7%) and etanercept the lowest (50.0%) reaching statistical difference (p < 0.001). The Kaplan-Meier analysis did not show a significant difference in drug survival in either the biologic-naïve or the biologic-experienced groups (p = 0.85). Multivariable analysis demonstrated a similar risk for discontinuation for etanercept, golimumab, and secukinumab compared with adalimumab, regardless of biologic-experience status. Conclusions: Adherence, drug survival, and risk for discontinuation were similar for all TNF-αis and the IL-17i SEC, regardless of biologic-experience status. As drug survival is an indirect measure of drug efficacy, n, in real-world settings, we believe caregivers can integrate these results into treatment considerations.

Clinical and imaging outcomes of different phenotypes of axial spondyloarthritis: 5-year analysis of the DESIR cohort

OBJECTIVES

To compare the long-term outcomes of three phenotypes of axial SpA (axSpA).

METHODS

Patients with a clinical diagnosis of axSpA from the DESIR cohort were grouped into three phenotypes at baseline: 'Pure axSpA' ('Axial'), 'axSpA with peripheral signs' ('IBP+Peripheral') and 'axSpA at risk' ('At risk') by latent class analysis. Clinical and imaging data were collected up to 5 years. Clinical outcomes, measured in each visit, included disability (BASFI) and quality of life (QoL; SF36). Imaging outcomes included inflammatory and structural lesions on MRI and radiographs of spine and SIJ. The association between phenotype membership at baseline and each outcome was tested in multivariable GEE models.

RESULTS

In total, 576 patients with axSpA were included. 'At risk' patients had worse disability and QoL than 'Axial' patients over time. For instance, 'At risk' patients had on average 0.4 more points in BASFI over time than 'Axial' patients [β (95 % CI): 0.4 (0.2; 0.7)]. This difference was mostly noted in female patients who were HLA-B27 positive. In addition, the difference between the 'At risk' and 'Axial' phenotypes was higher in patients receiving bDMARDs than in those not (β=0.6 vs 0.5), since BASFI improved more in 'Axial' (∆BASFI: -1.3) than in 'At risk' (∆BASFI: -0.9) treated patients. There were no differences in disability and QoL between 'Axial' and 'IBP+Peripheral' patients. Imaging outcomes were worse in the 'Axial' phenotype than in the others over time.

CONCLUSION

Patients with 'axSpA at risk' show worse self-reported outcomes over time and are less likely to benefit from anti-inflammatory treatment than those with a classical axSpA phenotype.

Increased Risk for Pulmonary Embolism among Patients with Ankylosing Spondylitis-Results from a Large Database Analysis

Background: Axial spondyloarthropathy(AS) is a chronic inflammatory disease primarily affecting the axial skeleton, often characterized by sacroiliitis. While pulmonary embolism (PE), a potentially lethal condition, has been linked to several autoimmune diseases, limited data exist regarding PE risk among patients with AS. Methods: This retrospective cohort study utilized the Clalit Healthcare Services (CHS) database, including 5825 patients with AS and 28,356 matched controls. Follow-up began at the date of first AS diagnosis for patients and at the matched patient's diagnosis date for controls and continued until PE diagnosis, death, or study end date. Results: Prevalence of PE before AS diagnosis in patients compared to controls was 0.4% vs. 0.2% (p < 0.01). The incidence rate of PE was 11.6 per 10,000 person-years for patients with AS and 6.8 per 10,000 person-years for controls. The adjusted hazard ratio (HR) for PE in patients with AS was 1.70 (p < 0.001). Subgroup analysis demonstrated excess risk for PE in patients with AS regardless of gender and age, with variations among AS treatment categories. Discussion: Our findings highlight a significant association between AS and PE, indicating an increased risk in patients with AS independent of age and sex and suggests a subclinical level of inflammation. Preliminary results suggest a protective role of immunosuppressing drugs. Further research into the impact of treatment strategies should be conducted and could inform clinical management and reduce the life-threatening risk of PE in Patients with AS.

Factors Associated With Treatment Pathways in Early Axial Spondyloarthritis: A Multistate Analysis of the 10-Year Follow-Up of the DESIR Cohort

OBJECTIVE

Current recommendations for the management of patients with axial spondyloarthritis (axSpA) emphasize the need of an individualized strategy in therapeutic decision-making. The study objectives were to describe therapeutic strategies observed in axSpA, and to assess the factors associated with treatment intensification over time.

METHODS

We included patients with axSpA from the French prospective cohort DESIR (Devenir des Spondylarthropathies Indifférenciées Récentes), with a scheduled 10-year follow-up. A multistate model with 4 ordered treatment states (no treatment, nonsteroidal antiinflammatory drugs [NSAIDs], conventional synthetic disease-modifying antirheumatic drugs [csDMARDs], and tumor necrosis factor inhibitors [TNFi]) was defined, with 6 possible transitions. Restricted mean sojourn times in each state were estimated. Then, predictors of those transitions were assessed by multivariable Cox models.

RESULTS

A total of 686/708 (96.9%) patients who had > 1 visit were analyzed. At cohort entry, 199 (29%) were untreated, 427 (62.2%) were receiving NSAIDs, 60 (8.7%) csDMARDs, and none were receiving TNFi. Over the follow-up period, patients mostly (46.4% of the time) received NSAIDs, followed by TNFi (24.4% of the time). The presence of sacroiliitis on radiographs, inflammatory bowel disease, and articular index were jointly associated with the transition to NSAIDs. Longer duration in the previous state often decreased the hazard of the transition to csDMARDs or TNFi. Worse disease activity outcomes increased the hazard of most transitions.

CONCLUSION

To our knowledge, this was the first study using a multistate model to easily represent different treatment states, detailing the transitions across them and their associated factors. Different time profiles for the management of patients with axSpA were identified, including in those abstaining from treatment up to a significant proportion of patients treated with csDMARDs.

Smoking and alcohol consumption are associated with peripheral musculoskeletal involvement in patients with spondyloarthritis (including psoriatic arthritis). Results from the ASAS-PerSpA study

BACKGROUND

An inverse association between alcohol consumption and disease activity and functional impairment has been observed in patients with spondyloarthritis (SpA). However, neither this association nor the influence of smoking has been investigated in peripheral manifestations of SpA.

OBJECTIVES

The objective of this study was to analyze the association between smoking and alcohol consumption and the presence of peripheral musculoskeletal manifestations (arthritis, enthesitis or dactylitis) and to determine the specific location of these manifestations.

METHODS

Patients from the worldwide cross-sectional ASAS-PerSpA study with a diagnosis of axial SpA (axSpA), peripheral SpA (pSpA) or psoriatic arthritis (PsA) according to their rheumatologist were included. Generalised linear mixed models used peripheral manifestation (or location) as a dependent variable, smoking status and alcohol consumption as fixed effects and country as a random effect. The interaction between smoking and alcohol was tested. Analyses were performed for each diagnosis (axSpA, pSpA and PsA).

RESULTS

A total of 4181 patients were included. In axSpA patients, smoking was associated with a lower prevalence of any peripheral manifestation, and current alcohol consumption was associated with a lower prevalence of both current arthritis and current enthesitis. In pSpA patients, current alcohol consumption was associated with a lower prevalence of current arthritis or enthesitis. In PsA patients, a significant association was found for arthritis with smoking and for enthesitis with alcohol consumption, and current alcohol consumption was associated with a lower prevalence of current arthritis or enthesitis.

CONCLUSION

Taking into account the country, smoking and alcohol are associated with a lower prevalence of peripheral manifestations.

ASAS-EULAR recommendations for the management of axial spondyloarthritis: 2022 update

OBJECTIVES

To update the Assessment of SpondyloArthritis international Society (ASAS)-EULAR recommendations for the management of axial spondyloarthritis (axSpA).

METHODS

Following the EULAR Standardised Operating Procedures, two systematic literature reviews were conducted on non-pharmacological and pharmacological treatment of axSpA. In a task force meeting, the evidence was presented, discussed, and overarching principles and recommendations were updated, followed by voting.

RESULTS

Five overarching principles and 15 recommendations with a focus on personalised medicine were agreed: eight remained unchanged from the previous recommendations; three with minor edits on nomenclature; two with relevant updates (#9, 12); two newly formulated (#10, 11). The first five recommendations focus on treatment target and monitoring, non-pharmacological management and non-steroidal anti-inflammatory drugs (NSAIDs) as first-choice pharmacological treatment. Recommendations 6-8 deal with analgesics and discourage long-term glucocorticoids and conventional synthetic disease-modifying antirheumatic drugs (DMARDs) for pure axial involvement. Recommendation 9 describes the indication of biological DMARDs (bDMARDs, that is, tumour necrosis factor inhibitors (TNFi), interleukin-17 inhibitors (IL-17i)) and targeted synthetic DMARDs (tsDMARDs, ie, Janus kinase inhibitors) for patients who have Ankylosing Spondylitis Disease Activity Score ≥2.1 and failed ≥2 NSAIDs and also have either elevated C reactive protein, MRI inflammation of sacroiliac joints or radiographic sacroiliitis. Current practice is to start a TNFi or IL-17i. Recommendation 10 addresses extramusculoskeletal manifestations with TNF monoclonal antibodies preferred for recurrent uveitis or inflammatory bowel disease, and IL-17i for significant psoriasis. Treatment failure should prompt re-evaluation of the diagnosis and consideration of the presence of comorbidities (#11). If active axSpA is confirmed, switching to another b/tsDMARD is recommended (#12). Tapering, rather than immediate discontinuation of a bDMARD, can be considered in patients in sustained remission (#13). The last recommendations (#14, 15) deal with surgery and spinal fractures.

CONCLUSIONS

The 2022 ASAS-EULAR recommendations provide up-to-date guidance on the management of patients with axSpA.

Uveitis in peripheral spondyloarthritis patients: an ancillary analysis of the ASAS-PerSpA study

Background:

Acute anterior uveitis (AAU) is the most frequent extra-musculoskeletal manifestation in spondyloarhtritis (SpA). Previous data on AAU focused on axial disease; therefore, it is not well known whether the clinical characteristics of patients with AAU and recurrent AAU differ between patients with axial and peripheral SpA.

Objective:

Primary objective was to compare the clinical characteristics of patients with AAU from patients without AAU in axial and peripheral spondyloarthritis (SpA) patients. Secondary objectives were to describe the clinical features of patients with AAU in the subset of patients with peripheral SpA (pSpA) and the clinical characteristics of patients with recurrent AAU in SpA patients.

Design:

This is an ancillary analysis of the ASAS-PerSpA study which included 3152 patients, 2719 patients with axSpA and 433 with pSpA according to rheumatologist judgement.

Methods:

Recurrent AAU was defined as the presence of two or more episodes of AAU ever. Univariable and multivariable binary logistic regression analyses were conducted to identify factors associated with the presence of AAU ever and the presence of recurrent AAU.

Results:

Overall, 663 patients (21%) presented AAU. Of them, 444 (66.9%) presented recurrent episodes. In patients with SpA, HLA-B27 positivity is the most important factor linked to the presence of AAU, odds ratio (OR) = 2.70 (95% CI = 2.04–3.6). In patients with pSpA, HLA-B27 positivity was also the most relevant factor linked to the presence of AAU, OR = 6.08 (95% CI = 2.72–15.68). Moreover, disease duration, younger age and higher body mass index (BMI) were the only factors slightly linked to the presence of recurrent episodes, OR = 1.03 (95% CI = 1.01–1.04), OR = 1.01 (95% CI = 1.00–1.03) and OR = 1.04 (95% CI = 1.01–1.08), respectively.

Conclusion:

HLA-B27 positivity is the most relevant factor linked to AAU risk in SpA patients, and this association is even stronger in those patients with pSpA. Moreover, our study did not find an association between HLA-B27 positivity and recurrent AAU in SpA patients.

What is peripheral spondyloarthritis? Identifying proportion, phenotype and burden in post hoc analysis of the ASAS-PerSpA study

BACKGROUND

Little is known about the prevalence, phenotype, and burden of peripheral spondyloarthritis (pSpA). The objective of the study is to compare the phenotype and burden of disease of pure pSpA to that of pure psoriatic arthritis (PsA), pure axial SpA (axSpA), and combined forms of SpA.

METHODS

This is a post hoc analysis of 4,185 patients from the cross-sectional ASAS-Peripheral involvement in SpA (PerSpA) study. Patients were approached in 2 ways: the first approach was based on the rheumatologist's diagnosis (diagnostic approach) and the second one was based on the fulfillment of ASAS or CASPAR classification criteria (classification criteria approach). Demographics, disease phenotype, and burden were compared among pure pSpA, PsA, axSpA, and the combined forms.

FINDINGS

The proportion of pSpA was 31.5% of SpA using the classification criteria approach and 10.3% using the diagnostic approach. pSpA was pure (i.e. without axSpA or PsA) in 16.8% of pSpA using the criteria, and in 62.3% using the diagnostic approach. Using classification criteria and diagnostic approach, respectively, pure pSpA patients had a high prevalence of peripheral joint disease (86 and 96%), synovitis (76 and 91%), and enthesitis (57 and 55%), a positive HLA-B27 in 65 and 59%, a high C-Reactive Protein level in 51% and inflammatory back pain in 52 and 42%. However, compared to pure PsA and pure axSpA, they had a significantly higher disease burden, but lower use of biologics using both approaches.

INTERPRETATION

The proportion of pSpA varies when using the classification criteria or the diagnostic approach. pSpA occurred in a pure form less frequently than PsA and axSpA and had intermediate features but a higher disease burden.

FUNDING

The PerSpA main study has been conducted under the umbrella of ASAS thanks to unrestricted grants from PFIZER, LILLY, ABBVIE, NOVARTIS, UCB, JANSSEN, MERCK.

A Case of Axial Spondyloarthritis Triggered by SARS-CoV-2 Infection

Ever since the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), there has been a noticeable change in atypical presentations of several rheumatological diseases following COVID-19 infections. In this case report, we present a case of SARS-CoV-2-induced axial and peripheral spondyloarthritis. This case highlights the possibility of SARS-CoV-2 infection accelerating the onset of autoimmune diseases such as axial spondyloarthritis. Although uncommon, these cases warrant a referral to the rheumatologist for appropriate diagnosis and management. This case also highlights the need for further research on the mechanisms behind the viral interaction of SARS-CoV-2 infections with the host immune system, especially about accelerating the onset of autoimmune diseases.

Enthesitis in patients with psoriatic arthritis and axial spondyloarthritis - data from the Danish nationwide DANBIO registry

OBJECTIVE

To explore the registration, pattern and burden of clinical enthesitis among routine-care patients with psoriatic arthritis (PsA) and axial spondyloarthritis (axSpA) in the Danish nationwide DANBIO registry.

METHODS

In patients with PsA and axSpA in DANBIO, prospectively registered data from 2010 to 2020 on clinical entheseal assessment using SPARCC score were compared with demographic, clinical and patient-reported-outcome (PRO) data.

RESULTS

6582 PsA and 5547 axSpA patients had their first registration in DANBIO in 2010 or later ("incident cohort"). At these registrations, 1037 (16%) PsA and 1188 (21%) axSpA patients had entheseal assessments, with ≥1 enthesitis being found in 66% and 39%, respectively. Mean enthesitis scores were 2.5 (PsA) and 1.3 (axSpA). Most common sites were: Achilles tendon (right/left/symmetrical: PsA:24.4%/23.3%/17.1%; axSpA:10.4%/10.6%/8.0%), lateral epicondyle (PsA:22.2%/20.1%/16.2%; axSpA:.4%/9.7%/7.6%), plantar fascia (PsA:17.1%/17.0%/12.6%; axSpA:10.4%/10.6%/8.0%), greater trochanter (PsA:14.2%/15.4%/11.7%; axSpA:9.9%/11.2%/8.2%). Enthesitis was more frequent in women (PsA/axSpA 61%/62%) than men (39%/37%). Patients with vs without enthesitis had higher overall burden (higher physician global, swollen/tender joint counts, pain, fatigue, patient global; fewer in patient-acceptable-symptom-state (PASS)) (all p < 0.05). Comparable demographic, clinical and PRO-results in patients with missing entheseal assessments, support the data being representative. In an "overall" cohort of all patients with ≥1 entheseal assessments after 2010, results on enthesitis were comparable.

CONCLUSION

Entheseal assessments were only performed at a minority of clinical visits. Clinical enthesitis was frequent, particularly in women, often symmetrical and associated with a higher physician- and patient-reported disease burden in patients with PsA and axSpA treated in routine practice, emphasizing the need for systematic assessment in routine care.

Cluster analysis in early axial spondyloarthritis predicts poor outcome in the presence of peripheral articular manifestations

OBJECTIVES

To assess whether two cluster analysis-based axial SpA (axSpA) endotypes (A for purely axial; B for both axial and peripheral) are stable over time and are associated with different long-term disease outcomes.

METHODS

K-means cluster analysis was performed at each visit (until 5 years) on 584 patients from the DESIR cohort, who completed all planned visits, and validated in 232 consecutive axSpA patients from the BeGiant cohort. Cluster stability overtime was assessed by kappa statistics. A generalized linear mixed-effect analysis was applied to compare outcomes between clusters. Classification and regression tree (CART) analysis was performed to determine a decision rule able to assign a given patient to a definite cluster at onset.

RESULTS

Both endotypes remained remarkably stable over time. In the DESIR cohort, patients in cluster B showed higher disease activity, worse functional outcome and higher need for anti-rheumatic drugs than patients in cluster A. CART analysis yielded three main clinical features (arthritis, enthesitis, and dactylitis) that accurately determined cluster assignment. These results could be replicated in the Be-GIANT cohort.

CONCLUSION

Cluster-based axSpA endotypes were reproducible in two different cohorts, stable over time and associated with different long-term outcome. The axSpA endotype with additional peripheral disease manifestations is associated with more severe disease and requires more intensive drug therapy.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov, https://clinicaltrials.gov, NCT01648907.

Axial spondyloarthritis

Axial spondyloarthritis (axSpA) encompasses both radiographic and non-radiographic axSpA. It is a chronic inflammatory disease with a predilection for involving the axial skeleton. The most common presenting symptoms are chronic back pain and spinal stiffness but peripheral and extra-musculoskeletal manifestations occur also frequently. The diagnosis of axSpA relies on the recognition of a clinical pattern of the disease, based on clinical, laboratory and imaging features. The Assessment in SpondyloArthritis international Society classification criteria for axSpA are valid and well implemented for research purposes. Sustained disease activity, measured by validated tools such as the Ankylosing Spondylitis Disease Activity Score, leads to irreversible structural damage and poor functioning and therefore should be abrogated. As part of the management algorithm, non-steroidal anti-inflammatory drugs remain as the first line of pharmacological treatment besides physiotherapy. As a second line, tumour necrosis factor inhibitor and interleukin-17 inhibitor are available but recently Janus kinase inhibitors have also shown efficacy in improving symptoms of the disease.

Peripheral arthritis and higher disease activity lead to more functional impairment in axial spondyloarthritis: Longitudinal analysis from ESPAXIA

OBJETIVE

The aim of this study was to investigate whether peripheral arthritis together with disease activity independently contribute to functional impairment over time in patients with axSpA and to evaluate if there are contextual factors modifying this relationship.

MATERIAL AND METHODS

Patients with axial spondyloarthritis from the ESPAXIA cohort were followed-up annually over a mean of 3.7 years. Physical function was assessed by the self-reported questionnaire BASFI, disease activity by ASDAS and peripheral arthritis was also recorded. Generalized estimating equations (GEE) were used to investigate longitudinal association between peripheral arthritis, ASDAS and BASFI as the outcome. Autoregressive models (adjusted for BASFI 1 year earlier) were run to allow for a truly longitudinal interpretation. Interactions between each of ASDAS and peripheral arthritis with contextual factors (age, gender, educational level, smoking, job type) were tested.

RESULTS

185 patients (77 % male, mean (SD) age 42 (13) years old and mean disease duration (SD) of 9.4 (9.6) years) were included. ASDAS and peripheral arthritis independently contributed to explaning BASFI over time. Contextual factors did not modify either of the relationships. A true longitudinal relation was proven with the autoregressive GEE model, showing that, adjusted for age, gender, spinal mobility and use of NSAIDs, an increase of one ASDAS unit led to a BASFI 0.48 units higher (ß 0.48 [95%CI 0.39, 0.57]), and the presence of peripheral arthritis, to a BASFI 0.44 units higher (ß 0.44 [95%CI 0.08, 0.8]).

CONCLUSION

Peripheral arthritis and higher disease activity independently lead to more functional impairment in axSpA over time. Contextual factors do not modify these relationships.

Uveitis occurrence in early inflammatory back pain. Five years data from the prospective French nationwide DESIR cohort

OBJECTIVE

Uveitis is a frequent extra rheumatological manifestation in axial Spondyloarthritis (SpA). The aim of study was to evaluate the prevalence and incidence of uveitis over the first five years of a prospective nationwide cohort of patients with high suspicion of early axial SpA, and to evaluate its associated factors.

METHODS

DESIR is a prospective observational cohort of patients with recent onset inflammatory back pain (more than 3 months, less than 3 years), suggestive of axial SpA, All available factors in the database were compared between patients with and without uveitis at 5 years, by uni and then multivariate analysis. Baseline factors associated with new cases of uveitis occurrence over the 5 years were also analyzed.

SIGNIFICANCE

P less than 0.05.

RESULTS

After 5 years, 91 patients (out of 480 with complete follow-up) had at least one uveitis episode, giving an estimated prevalence of 18.9% [95% CI: 15.4-22.4]. In multivariate analysis, uveitis was significantly associated with dactylitis, and elevated ESR. New incident uveitis occurred in 31 cases over 5 years, giving an estimated incidence rate of 1.29 [0.84-1.74]/100 patient-years. Incidence of new uveitis was associated in multivariate analysis with baseline factors: diagnosis of SpA, sacro iliac MRI inflammatory SPARCC score, dactylitis, syndesmophyte score. No significant association was found with HLA-B27, DMARDs, BASDAI, ASDAS, BASFI.

CONCLUSION

Five-years data of the DESIR cohort allowed an estimation of incidence rate of uveitis of 1.3/100p-y; over five years, uveitis was associated with dactylitis, biologic and sacro iliac MRI inflammation.

Smoking in spondyloarthritis: unravelling the complexities

Tobacco smoking is a major threat to health. There is no doubt about the need to promote and support cessation at every opportunity. Smoking has a clear role in RA, but what evidence is there that the same relationship exists in SpA? In this review, we examine (the less cited) paradoxes and contradictions in the existing axial SpA (axSpA) and PsA literature; for example, smoking appears to be 'protective' for some axSpA manifestations. We also highlight findings from higher quality evidence: smoking is associated with increased risk of PsA and the risk of psoriasis in axSpA. The relationship between smoking and SpA is far from simple. Our aim is to highlight the harms of smoking in SpA and bring attention to inconsistencies in the literature to inform further research.

What is axial spondyloarthritis? A latent class and transition analysis in the SPACE and DESIR cohorts

Objectives

To gain expert-judgement-free insight into the Gestalt of axial spondyloarthritis (axSpA), by investigating its ‘latent constructs’ and to test how well these latent constructs fit the Assessment of SpondyloArthritis international Society (ASAS) classification criteria.

Methods

Two independent cohorts of patients with early onset chronic back pain (SPondyloArthritis Caught Early (SPACE)) or inflammatory back pain (IBP) (DEvenir des Spondylarthopathies Indifférenciées Récentes (DESIR)) were analysed. Latent class analysis (LCA) was used to estimate the (unobserved) potential classes underlying axSpA. The best LCA model groups patients into clinically meaningful classes with best fit. Each class was labelled based on most prominent features. Percentage fulfilment of ASAS axSpA, peripheral SpA (pSpA) (ignoring IBP) or both classification criteria was calculated. Five-year data from DESIR were used to perform latent transition analysis (LTA) to examine if patients change classes over time.

Results

SPACE (n=465) yielded four discernible classes: ‘axial’ with highest likelihood of abnormal imaging and HLA-B27 positivity; ‘IBP+peripheral’ with 100% IBP and dominant peripheral symptoms; ‘at risk’ with positive family history and HLA-B27 and ‘no SpA’ with low likelihood for each SpA feature. LCA in DESIR (n=576) yielded similar classes, except for the ‘no-SpA’. The ASAS axSpA criteria captured almost all (SPACE: 98%; DESIR: 93%) ‘axial’ patients, but the ‘IBP+peripheral’ class was only captured well by combining the axSpA and pSpA criteria (SPACE: 78%; DESIR: 89%). Only 4% of ‘no SpA’ patients fulfilled the axSpA criteria in SPACE. LTA suggested that 5-year transitions across classes were unlikely (11%).

Conclusion

The Gestalt of axSpA comprises three discernible entities, only appropriately captured by combining the ASAS axSpA and pSpA classification criteria. It is questionable whether some patients with ‘axSpA at risk’ will ever develop axSpA.