Research ArticleSpondyloarthritis

Factors Associated With Residual Disease in Axial Spondyloarthritis: Results From a Clinical Practice Registry

Casper Webers, Annelies Boonen, Harald E. Vonkeman and Astrid van Tubergen
The Journal of Rheumatology November 2023, 50 (11) 1430-1438; DOI: https://doi.org/10.3899/jrheum.2023-0194

Abstract

Objective To explore residual disease, defined as substantial symptoms and disease burden despite a remission or low disease activity (LDA) state, in patients with axial spondyloarthritis (axSpA), and to determine which factors are associated with residual disease.

Methods For this cross-sectional observational study, 1 timepoint per patient was used from SpA-Net, a web-based monitoring registry for SpA. Patients with an Ankylosing Spondylitis Disease Activity Score (ASDAS) < 2.1 (LDA) were included. Indicators of residual disease (outcomes) included fatigue (primary outcome), pain, physical functioning, health-related quality of life (HRQOL), and peripheral symptoms. Sex was the primary explanatory factor for residual disease. Other explanatory factors included demographics and disease-related factors. Associations between these factors and presence and extent of residual disease were explored using logistic and linear regression.

Results In total, 267 patients in an LDA state were included. Mean age was 50.6 (SD 14.3) years and 100 (37.5%) were female. Residual disease occurred frequently (n = 114 [42.7%] had fatigue scores > 4/10; n = 34 [17.8%] had pain scores > 4/10), including in those in remission (ASDAS < 1.3). Physical HRQOL was reduced in 27% and moderate/poor in 33%. Multivariable regression analyses showed that reported fatigue was more severe and prevalent in female patients (fatigue severity [0–10]: Bfemale = 0.78, 95% CI 0.18-1.38; fatigue > 4/10: ORfemale = 3.29, 95% CI 1.74-6.20). Other indicators of residual disease (ie, pain, peripheral symptoms, physical HRQOL) were also more severe and/or more prevalent in females.

Conclusion Residual disease is frequent in patients with axSpA who are in an LDA state, including remission, and it is particularly prevalent in female patients. Future studies should address how to manage or prevent residual disease in axSpA.

Key Indexing Terms:

Axial spondyloarthritis (axSpA) is a chronic inflammatory disorder of the lower spine and sacroiliac joints.1 The key symptom is lower back pain, although other musculoskeletal sites are often also involved. In addition, extramusculoskeletal manifestations (EMMs; anterior uveitis, inflammatory bowel disease [IBD], and psoriasis [PsO]) can be present. The treatments for axSpA include nonsteroidal antiinflammatory drugs (NSAIDs), biologic disease-modifying antirheumatic drugs (bDMARDs), targeted synthetic DMARDs (tsDMARDs), and occasionally, if peripheral symptoms occur, conventional synthetic DMARDs (csDMARDs).2 Due to the chronic nature of the disease and its early onset in life, the burden for patients and society is substantial.3,4

In the management of axSpA, disease activity is an important outcome. Disease activity reflects the symptoms of axSpA,5 and higher disease activity is associated with greater progression of structural damage to the spine.6 According to international recommendations, disease activity should be measured regularly, and low disease activity (LDA) or remission should be aimed for.7 Disease activity in axSpA is assessed with the Ankylosing Spondylitis Disease Activity Score (ASDAS). Remission and LDA are defined as ASDAS scores < 1.3 and < 2.1, respectively.8 These disease activity targets are used to guide treatment decisions.9,10 In current practice, however, even patients who achieve these targets can still experience substantial symptoms and disease burden.11 Examples of such residual disease are specific symptoms like pain and fatigue (ie, residual symptoms), signs of inflammation such as enthesitis, and also impairments in general health and functioning. These can affect patients’ daily lives, and potentially contribute to the broader disease impact. Currently, there are no recommendations on how to manage residual disease.

The phenomenon of residual disease has repeatedly been shown in other rheumatic diseases, such as psoriatic arthritis and rheumatoid arthritis.11-14 In axSpA, however, only 2 studies to our knowledge have investigated residual disease.11,15 About half of patients who were in an LDA state still had fatigue or pain. Additionally, female and older patients were more likely to experience fatigue, although analyses were not adjusted for potential confounders and were limited to fatigue and pain.15 Previous research has also shown that female patients with axSpA report more severe symptoms in general.16,17 As such, sex is an interesting candidate risk factor to investigate in the context of residual disease, as this information could be used to identify those more vulnerable in daily practice.

The aim of this study was to determine to what extent a variety of different indicators of residual disease are present in patients with axSpA who are in remission or an LDA state in daily practice, and to explore which patient and disease characteristics (with a particular focus on sex) are associated with the presence and extent of residual disease.

METHODS

Study design and study population. Our cross-sectional, observational study was conducted within SpA-Net, a disease-specific integrated web-based system for Dutch patients with SpA (International Clinical Trials Registry Platform registration no. NTR6740).18 SpA-Net was launched in 2016 and is used in 2 large hospitals.

All patients with a prevalent or incident clinical diagnosis of SpA who are under rheumatologists’ care in participating centers are consecutively included in SpA-Net as part of routine care. Aside from a clinical diagnosis of SpA, there are no additional inclusion/exclusion criteria for participation in SpA-Net. Participants are prospectively monitored over time in daily practice. They complete questionnaires at home prior to their outpatient visits, during which these questionnaires are reviewed and additional data, such as physician-based outcomes, are registered. As SpA-Net is a daily practice registry, the frequency of visits is not fixed but varies between patients. Changes in disease management are left to the discretion of the treating rheumatologists.

For our present study, all patients with an axSpA diagnosis were eligible if they had data available on the ASDAS and on ≥ 1 indicator of residual disease (see Outcomes). If multiple timepoints for a patient met these criteria, the most recent complete assessment of the patient in an LDA state—or high disease activity (HDA) state if never in an LDA state—was chosen for analysis. Our goal was to explore a wide range of indicators of residual disease in current practice and under current management, which is why we chose the most recent, complete assessment.

The ethics committee of the University Hospital Maastricht/Maastricht University determined that observational studies involving SpA-Net were not subject to the Medical Research Involving Human Subjects Act as data were collected in routine care, and official approval was not required for this study (METC azM/UM 15-4-266). Written informed consent was obtained from each patient to use data for research.

Disease activity categories. Disease activity is measured with the ASDAS, which combines patient-reported outcome measures with a laboratory biomarker for inflammation (C-reactive protein [CRP]).19 Disease activity states were defined as LDA (ASDAS < 2.1, including patients in remission [inactive disease, ASDAS < 1.3] or nonremission LDA [1.3 ≤ ASDAS < 2.1]) or HDA (ASDAS ≥ 2.1).8 The ASDAS and ASDAS-based disease activity states have been validated and endorsed.20,21

Explanatory factors for residual disease. Sex was the primary explanatory factor. Additional factors included other patient characteristics (ie, age, education, employment, smoking) as well as disease-related factors (ie, symptom duration, history of EMMs, type of current therapy [NSAID, cs/b/tsDMARD]).

Patient characteristics were either collected upon inclusion (age and sex) or updated every 2 years (education and smoking) or 6 months (employment). Education was dichotomized (high vs other). Employment was collected as part of the Work Productivity and Activity Impairment questionnaire (employed vs not employed).22 Former smokers and never smokers were grouped and compared with current smokers.

Disease-related factors were collected upon inclusion (symptom duration) or updated on indication (current therapy and history of anterior uveitis, IBD, and/or PsO), and bDMARDs and tsDMARDs were grouped.

Outcomes. Indicators of residual disease were fatigue (primary outcome); pain; physical functioning; enthesitis, dactylitis, or peripheral arthritis; health-related quality of life (HRQOL); physician global assessment (PhGA) of disease activity; and acceptance of current state according to patient and physician (Supplementary Table S1, available with the online version of this article).

Fatigue (range 0-10) was assessed with the first item of the Bath Ankylosing Spondylitis Disease Activity Index.23-25 Pain (axSpA-related, occurring within the past week) was assessed with a visual analog scale (VAS, range 0-10). Physical functioning (range 0-10) was measured with the Bath Ankylosing Spondylitis Functional Index (BASFI).26 As validated thresholds for these indicators were lacking, fatigue, pain, and BASFI scores > 2/10 and > 4/10 were considered clinically relevant. Clinical inflammation included peripheral arthritis, enthesitis, and dactylitis (swollen joint count [SJC, range 0-66] and tender joint count [range 0-68], entheses [range 0-65], and digits [range 0-20]), and was assessed by a physician. Presence of any swollen joints, enthesitis, or dactylitis (count ≥ 1) was considered relevant clinical inflammation.

HRQOL was measured with the generic 36-item Short Form Health Survey (SF-36), the EuroQoL-5 Dimension questionnaire (EQ-5D) VAS, and the disease-specific Assessment of SpondyloArthritis international Society Health Index (ASAS HI, range 0-17).27-29 The SF-36 was summarized in a physical component summary (PCS) and mental component summary (MCS; range 0-100), with PCS and MCS scores < 40/100 considered as a relevant impairment in HRQOL.30 ASAS HI–based health states are as follows: good (ASAS HI ≤ 5), moderate (5 < ASAS HI < 12), and poor (ASAS HI ≥ 12).31 The rheumatologist’s assessment of disease activity was captured with a single VAS (PhGA, range 0-10), with scores > 2/10 indicating relevant disease activity. Finally, acceptance of the current health state was used as an indicator of residual disease, and was assessed with the Patient Acceptable Symptom State (PASS). PASS is a single question for patients and physicians, asking whether it would be acceptable if the patient’s current disease state remained unchanged for the next months. PASS was added to SpA-Net in June 2020, several years after its initial launch.

For all measurements, except SF-36 PCS and MCS and EQ-5D VAS, higher scores indicated a worse outcome. The fatigue item, pain VAS, PASS, and PhGA were completed during every visit in SpA-Net, whereas the ASAS HI was completed every 3 months and BASFI, SF-36, and EQ-5D were completed every 6 months (depending on the frequency of rheumatologist visits). Joint, enthesitis, and dactylitis counts were completed on indication.

Statistical analysis. Patient and disease characteristics were described for the overall population and by disease activity state. Next, within the group of patients in an LDA state, the severity and prevalence of indicators of residual disease were described (for LDA and separately for remission and nonremission LDA). The following thresholds were used to identify clinically relevant disease: > 2/10 and > 4/10 for fatigue, pain, and BASFI; < 40/100 for SF-36 PCS and MCS; > 5/17 for ASAS HI; SJC, enthesitis, and dactylitis count ≥ 1; and PhGA > 2/10.

For regression analyses, patients in remission and nonremission LDA were grouped because of sample size. Linear regression analyses were conducted to assess whether sex was associated with severity of residual disease. Other potential explanatory factors were education, employment, smoking, history of EMMs, and current medication (all binary), as well as age and symptom duration (both continuous). Each continuous outcome (fatigue, pain, physical functioning, HRQOL, PhGA) was explored in a separate regression analysis. First, all potential explanatory factors (including sex) were tested in univariable analysis. Second, if sex was potentially associated with the outcome (P < 0.20), this was further tested in a multivariable model. Starting with sex, other explanatory factors potentially associated with the outcome (P < 0.20 in univariable analysis) were added consecutively to the model in a prespecified order. Factors were retained if they were significant (P < 0.05) when entered in this model or if they were a confounder (changed the coefficient of sex by > 10%). Notably, if sex was not potentially associated with an outcome, no multivariable analysis was conducted.

Factors associated with the presence of residual disease were investigated with logistic regression analyses. These analyses were conducted for all binary outcomes (fatigue, pain, and physical functioning [BASFI] scores > 4/10 or > 2/10; HRQOL score < 40/100 [SF-36] or > 5/17 [ASAS HI]; presence of peripheral symptoms; acceptance of current state; and PhGA > 2/10). The same modeling strategy was used as for linear regression.

Four sensitivity analyses were conducted. First, regression analyses were repeated with ASDAS state (remission vs nonremission LDA) as a covariable in the model. Second, the analysis of the primary outcome (fatigue) was repeated in those who were in LDA at ≥ 2 consecutive visits with ≥ 3 months between (persistent LDA). Third, the analysis of the primary outcome was repeated in patients who had none of the other outcomes missing (completers; missing PASS was allowed, as this was later introduced in SpA-Net). Fourth, a manual backward method was explored (starting with all variables with P < 0.20 in univariable analysis, eliminating nonsignificant variables one by one) to account for potential suppressor effects. Missing data were not imputed. Interactions were tested and, if significant, analyses were stratified. P < 0.05 was considered statistically significant. Analyses were performed in Stata 14.2 (StataCorp).

RESULTS

Population characteristics. In total, 396 patients were included (Supplementary Table S2 and Supplementary Figure, available with the online version of this article). Of these, 267 patients (67.4%) were in an LDA state at some point during follow-up and were included in the LDA subgroup (186/267 [69.7%] nonremission LDA, 81/267 [30.3%] remission; Table 1). The remaining 129 were never in an LDA state during follow-up, constituting the HDA subgroup. In the total population, mean age was 50.6 (SD 14.4) years and 169 patients (42.7%) were female (Supplementary Table S2). The majority were HLA-B27 positive (75.5%), the mean ASDAS was 2.1 (SD 0.9), and about half were on bDMARD treatment. In the LDA and HDA subgroups, most patient characteristics were similar, although patients in LDA were more often highly educated and employed (Supplementary Table S2). Within the LDA group, patients in remission (ASDAS < 1.3), compared to those not in remission (1.3 ≤ ASDAS < 2.1), were less likely to be female (25.9% vs 42.5%, Table 1).

View this table:
Table 1.

Population characteristics in the overall LDA group and by remission or nonremission state.

Prevalence of residual disease. Of 267 patients in the LDA subgroup, 218 (81.7%) had ≥ 1 indicator of residual disease. Fatigue was particularly prevalent (n = 177 [66.3%] and n = 114 [42.7%] patients had scores of > 2/10 and > 4/10, respectively; Table 2). Pain and limitations in physical function (> 4/10) were present in approximately 1 in 6 patients. A quarter of patients had reduced physical HRQOL (SF-36 PCS < 40/100), or moderate or poor disease-specific HRQOL (ASAS HI > 5/17). Patients with ≥ 1 indicator of residual disease often had multiple indicators (Figure 1). Nonetheless, the majority of patients and their physicians considered the current state of the patient as acceptable (PASS-patient 88.8%, PASS-physician 97.1%).

View this table:
Table 2.

Residual disease in patients with LDA (ASDAS < 2.1).

Figure 1.
Figure 1.

Relationship and overlap between indicators of residual disease. Number and percentage of patients with residual disease (note: not all indicators of residual disease are shown). The percentages in the diagrams are based on the population of patients that had ≥ 1 of the indicators of residual disease included in the diagram. For the indicators of residual disease shown in Figure 1A, 97 patients (60% of total) had ≥ 1 indicator and 57 patients (35% of total, 59% of those with ≥ 1 indicator) had ≥ 2 indicators. For the indicators of residual disease shown in Figure 1B, 69 patients (61% of total) had ≥ 1 indicator and 34 patients (30% of total, 49% of those with ≥ 1 indicator) had ≥ 2 indicators. ASAS HI: Assessment of SpondyloArthritis international Society Health Index; BASFI: Bath Ankylosing Spondylitis Functional Index; HRQOL: health-related quality of life.

Within the LDA subgroup, 54/81 of those in remission and 164/186 of those in nonremission LDA had ≥ 1 indicator of residual disease. Again, fatigue was particularly prevalent (Figure 2).

Figure 2.
Figure 2.

Residual disease indicators in patients with ASDAS < 2.1 by disease activity state. For all outcomes, except PASS, a higher percentage reflects higher prevalence of residual disease. ASAS HI: Assessment of SpondyloArthritis international Society Health Index; ASDAS: Ankylosing Spondylitis Disease Activity Score; BASFI: Bath Ankylosing Spondylitis Functional Index; LDA: low disease activity; MCS: mental component summary; PASS: patient acceptable symptom state; PCS: physical component summary; SF-36: 36-item Short Form Health Survey.

When comparing the prevalence of the different indicators by sex (primary explanatory factor), prevalence was consistently higher in females (Table 2). Differences were especially striking for fatigue (> 4/10: 54% of females vs 35.9% of males), peripheral symptoms (21.2% vs 4.5%), and physical HRQOL (SF-36 PCS < 40/100: 38% vs 19%; ASAS HI > 5/17: 44.4% vs 24.2%; Table 2).

Factors explaining residual disease. Full regression results are shown in Supplementary Tables S3-23 (available with the online version of this article). In univariable linear regression analyses, sex was potentially associated (P < 0.20) with severity of fatigue, ASAS HI, SF-36 PCS, and PhGA. In addition, due to interaction, analyses were stratified for pain and for BASFI. Sex was potentially associated (P < 0.20) with pain in nonemployed patients (but not in employed patients), and with BASFI in patients with a history of PsO (but not in patients without a history of PsO; Table 3). In multivariable linear regression analyses, the association between sex and these indicators of residual disease was maintained. Females had significantly worse levels of fatigue (B 0.78, 95% CI 0.18-1.38), pain (B 1.48, 95% CI 0.46-2.51 [nonemployed patients only]), ASAS HI (B 1.91, 95% CI 0.99-2.82), SF-36 PCS (B −3.55, 95% CI −5.82 to −1.28), and PhGA (B 0.38, 95% CI 0.04-0.72; Table 3). No associations were observed between sex and mental HRQOL or EQ-5D VAS in linear regression.

View this table:
Table 3.

Associations between sex and residual disease in univariable and multivariable linear regression models in patients with ASDAS < 2.1.

Several other factors were associated with the severity of residual disease. Higher age was associated with less fatigue but worse PhGA; being employed with better ASAS HI and SF-36 PCS; a history of IBD with worse fatigue ASAS HI and SF-36 PCS; current use of NSAIDs with better ASAS HI; and bDMARDs with worse fatigue (Supplementary Tables S3-10, available with the online version of this article).

Logistic regression analysis of the presence of clinically relevant residual disease yielded similar results (Table 4). In univariable logistic regression analysis, sex was potentially associated (P < 0.20) with presence of fatigue, pain, moderate-to-poor ASAS HI, and PASS-patient (in the total population), as well as with high BASFI (employed subgroup only) and presence of peripheral symptoms (low education subgroup only). In multivariable analyses, most of these associations were maintained (Table 4). Females were significantly more likely to have fatigue (> 4/10: odds ratio [OR] 3.29, 95% CI 1.74-6.20), pain (> 4/10: OR 2.81, 95% CI 1.24-6.38), high BASFI (> 4/10: OR 7.06, 95% CI 1.33-37.62 [employed only]), peripheral symptoms (OR 24.69, 95% CI 2.89-210.99 [low education only]), moderate or poor ASAS HI (OR 2.72, 95% CI 1.35-5.46), and reduced physical HRQOL (OR 2.67, 95% CI 1.33-5.36). No associations were observed between sex and mental HRQOL, PASS, or PhGA in logistic regression.

View this table:
Table 4.

Associations between sex and residual disease in univariable and multivariable logistic regression models in patients with ASDAS < 2.1.

Several factors were associated with the prevalence of residual disease. Higher age was associated with less frequent fatigue and reduced SF-36 PCS; being employed with less frequent pain; a history of IBD with more frequent fatigue and worse ASAS HI; a history of PsO with more frequent impaired physical function (BASFI); and current use of NSAIDs with more frequent peripheral involvement (Supplementary Tables S11-23, available with the online version of this article).

Sensitivity analyses. The sensitivity analyses confirmed the results of the main analyses. Additional adjustment for ASDAS state (remission vs nonremission LDA) slightly reduced the strength of association for some outcomes but still yielded clinically relevant and statistically significant associations between sex and residual disease (Supplementary Table S24 and Supplementary Table S25, available with the online version of this article). Analyses in those with ASDAS < 2.1 at 2 consecutive visits (persistent LDA) and those who had all outcomes nonmissing (completers) also led to similar results (Supplementary Tables S26-32). Finally, using a backward instead of a forward method resulted in similar results (and often the exact same models; data not shown).

DISCUSSION

In our observational study, a wide variety of indicators of residual disease, including patient-reported and physician-reported indicators, were prevalent in a substantial proportion of patients with axSpA who were in an LDA state (ASDAS < 2.1), including patients who were in remission (ASDAS < 1.3). Most indicators of residual disease were both more frequent and more severe in female patients compared to male patients, independent of other explanatory factors. This included specific symptoms such as pain and fatigue, but also the broader experience of HRQOL (functioning and health).

In axSpA, 2 studies that we know of have investigated residual disease in patients with axSpA.11,15 The reported prevalence of residual symptoms was similar to that which we observed. In one of these studies, female patients were more likely to experience fatigue (but not pain), but these were unadjusted analyses.15 In our study, for the first time in axSpA, we explored which factors were associated with different indicators of residual disease while also accounting for confounders. Sex explained both the prevalence and severity of residual disease. Our observations fit within the sex/gender disparity in axSpA. Female patients typically have a longer delay in diagnosis, report worse scores on patient-reported outcome measures, and have a lower treatment response, whereas male patients tend to have higher levels of CRP and more progression of structural damage.16,17,32,33 We can only speculate on potential explanations for our observations. Female patients with axSpA might have a different phenotype, resulting in certain symptoms being more dominant when compared to male patients.34 Alternatively, female and male patients might experience (or report) their symptoms differently. Pain mechanisms, for example, are influenced by sex hormones, and females and males differ in the number and expression of pain receptors.17 Sex differences in psychological and social context could also affect symptom experience.35 Further, female patients may be relatively undertreated. In support of this, female patients were more likely to have physician-assessed peripheral symptoms, in line with other studies.34 In addition, male patients were more likely to be in remission (ASDAS < 1.3) compared to female patients in our study. This could indicate that, even though these female patients have already achieved a low level of disease activity, there might still be room for further improvement of their disease state.

Regardless of the underlying mechanisms, residual disease is relevant for daily practice. Not all patients can achieve remission, and nonremission LDA is considered an alternative target.10,36 One might expect some remaining disease burden in patients who are in a nonremission LDA state as they are, by definition, not in remission; however, we demonstrate that most of these patients have clinically relevant symptoms. Further, even among those who are actually in remission, over half of patients experienced some form of residual disease. Not only did we observe specific residual symptoms such as pain or fatigue, but the broader outcome of HRQOL was also affected. Interestingly, despite these symptoms, almost 90% of patients considered themselves to be in an acceptable symptom state. Adaptation might play a role here, and an acceptable state likely differs from the optimal one.

Our observations also suggest that some aspects of the disease are not (sufficiently) captured by the ASDAS, or that the endorsed cut-offs are not fit for daily practice. For example, a history of EMMs was associated with several indicators, and it might be that some of these patients still experience symptom or disease burden due to EMMs. We should emphasize that this does not necessarily mean that the ASDAS is not a good measure or target for disease management. Part of our study population already had established disease, and using ASDAS targets in early axSpA might lead to less residual disease. However, our results do suggest that other targets might need to be considered as well. Finally, one-third of patients in our cohort did not achieve an ASDAS < 2.1 at any point during follow-up (the HDA group), highlighting another challenging issue in daily practice.

Our study has several strengths. SpA-Net is a daily practice registry. We were able to investigate residual disease in the whole spectrum of axSpA, and the results are likely generalizable. In addition, despite a lack of instruments specifically designed to assess residual disease, we used validated measures for most outcomes. As established thresholds for (residual) fatigue, pain, and limitations in physical functioning are lacking, we included a strict threshold of 4/10 to be specific, yet we also explored a lower threshold of 2/10 for comparative purposes.11 Of note, none of these thresholds were validated. Due to the broad range of patient-reported and physician-assessed outcomes collected in SpA-Net, we could investigate a wide variety of potentially relevant indicators for residual disease.

Our current study also has limitations. First, as this was a cross-sectional study, no firm conclusions can be drawn regarding causality. Notably, our primary explanatory factor (sex), as well as several secondary factors, were fixed over time. Second, because of limited sample size, we grouped patients in remission and nonremission LDA in the regression analyses. Third, for most outcomes, there were missing data; however, for the primary outcome (fatigue), data were complete, and a completer analysis led to similar results. Fourth, although we had data on several patient and disease-related factors that could explain residual disease, it is possible that residual confounding occurred. For example, information on psychological factors was unavailable.

In conclusion, in clinical practice most patients in an LDA state (including remission) have residual disease, and female patients are more likely to report this. Future studies should address how to best understand and manage residual disease in order to optimize the short-term and long-term health of all patients with axSpA.

Footnotes

  • No specific funding was received from any bodies in the public, commercial, or not-for-profit sectors to carry out the work described in this article. SpA-Net was financially supported by grants from The Netherlands Organisation for Health Research and Development (ZonMw, project no. 836042001) and Dutch Arthritis Society, and was additionally sponsored by AbbVie, Biogen, Celgene, Janssen-Cilag, MSD, Novartis, Pfizer, and UCB.

  • HEV has received consulting fees or honorarium from AbbVie, Novartis, Pfizer, UCB, Janssen, and Galapagos, all outside the submitted work. AvT has received unrestricted research grants related to SpA-Net from Novartis, Pfizer, and UCB, and received consulting fees from Galapagos, Novartis, and UCB. CW and AB declare no conflicts of interest relevant to this article.

  • Accepted for publication July 4, 2023.

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Keywords

AXIAL SPONDYLOARTHRITIS
DISEASE ACTIVITY
REGISTRY
residual disease

Keywords