Predicting a diagnosis of ankylosing spondylitis using primary care health records-A machine learning approach

Ankylosing spondylitis is the second most common cause of inflammatory arthritis. However, a successful diagnosis can take a decade to confirm from symptom onset (via x-rays). The aim of this study was to use machine learning methods to develop a profile of the characteristics of people who are likely to be given a diagnosis of AS in future. The Secure Anonymised Information Linkage databank was used. Patients with ankylosing spondylitis were identified using their routine data and matched with controls who had no record of a diagnosis of ankylosing spondylitis or axial spondyloarthritis. Data was analysed separately for men and women. The model was developed using feature/variable selection and principal component analysis to develop decision trees. The decision tree with the highest average F value was selected and validated with a test dataset. The model for men indicated that lower back pain, uveitis, and NSAID use under age 20 is associated with AS development. The model for women showed an older age of symptom presentation compared to men with back pain and multiple pain relief medications. The models showed good prediction (positive predictive value 70%-80%) in test data but in the general population where prevalence is very low (0.09% of the population in this dataset) the positive predictive value would be very low (0.33%-0.25%). Machine learning can be used to help profile and understand the characteristics of people who will develop AS, and in test datasets with artificially high prevalence, will perform well. However, when applied to a general population with low prevalence rates, such as that in primary care, the positive predictive value for even the best model would be 1.4%. Multiple models may be needed to narrow down the population over time to improve the predictive value and therefore reduce the time to diagnosis of ankylosing spondylitis.

How good is the agreement between clinical diagnoses and classification criteria fulfilment in axial spondyloarthritis? Results from the SPARTAKUS cohort

OBJECTIVES

To study the agreement between clinical axial spondyloarthritis (axSpA) diagnoses and fulfilment of the Assessment of SpondyloArthritis international Society (ASAS) axSpA and modified New York (mNY) classification criteria, and to compare disease/health status between axSpA subtypes.

METHOD

Patients with prevalent, clinical axSpA attending a rheumatology clinic were enrolled in a cross-sectional study. Assessments included physical evaluation, laboratory testing, questionnaires, and appropriate imaging, allowing classification. Standard axSpA outcome measures were compared between patients fulfilling mNY/radiographic versus non-radiographic axSpA (r-axSpA/nr-axSpA) criteria.

RESULTS

Of 239 consecutively included patients, 141 fulfilled ASAS r-axSpA and/or mNY criteria, while 57 fulfilled nr-axSpA criteria. The agreement between r-axSpA and mNY criteria fulfilment was 94%. The positive predictive value (PPV) of a clinical ankylosing spondylitis (AS) diagnosis for mNY criteria fulfilment was 71%; the PPV of an undifferentiated axSpA (u-axSpA) diagnosis for fulfilment of nr-axSpA criteria was 30% and 40% for mNY criteria. Patients with r-axSpA/AS were older, more often men, and had longer disease duration, more uveitis, and worse spinal mobility than nr-axSpA patients, who had more enthesitis and dactylitis.

CONCLUSION

We found an overall good concordance between clinical axSpA diagnoses and classification criteria fulfilment, with 83% fulfilling ASAS axSpA and/or mNY criteria. Regarding axSpA subtypes, the concordance was weaker, and although the ICD-10 code for AS correctly identified patients meeting mNY criteria in 71% of cases, one-third of mNY-positive patients lacked an AS diagnosis. Moreover, clinical u-axSpA diagnoses could not serve as a proxy to identify nr-axSpA, highlighting the importance of thorough classification in research on axSpA subtypes.

Prevalence and consequences of psoriasis in recent axial spondyloarthritis: an analysis of the DESIR cohort over 6 years

OBJECTIVES

The consequences of psoriasis associated to axial spondyloarthritis (axSpA) are unclear. The objectives were to determine the prevalence and the consequences of psoriasis in recent axSpA over 6 years of follow-up.

METHODS

The multicentric prospective cohort DESIR (NCT01648907) of adult patients with recent inflammatory back pain suggestive of axSpA was analysed over 6 years. Psoriasis was recorded at each visit and cumulative prevalence and incidence were calculated. Patients with vs without psoriasis at any time point were compared. Outcomes included disease activity (Ankylosing Spondylitis Disease Activity Score-C reactive protein (ASDAS-CRP), joint and enthesitis count, CRP), patient-reported outcomes for function (Health Assessment Questionnaire for axSpA, HAQ-AS) and quality of life, and treatment use over 6 years. Outcomes were compared through univariable and multivariable analyses, as well as linear mixed effect models.

RESULTS

In 589 patients, mean age 40.5±8.7 years, 45.8% men and baseline mean symptom duration 1.5±0.9 years, the cumulative prevalence of psoriasis increased from 16.8% (99/589) at baseline to 26.8% (158/589) at 6 years, leading to an incidence of 2.1/100 patient-years. Over 6 years of follow-up, patients with psoriasis developed more synovitis (p=0.008), and received more methotrexate (cumulative use, 25.5% vs 11.8%, p<0.001) and biological disease-modifying drugs (55.7% vs 38.5%, p<0.001). There were no significant consequences of psoriasis on other outcomes, including disease activity (ASDAS-CRP), functional capacity (HAQ-AS) and quality of life.

CONCLUSION

Psoriasis is frequent in early axSpA. AxSpA patients with psoriasis had more swollen joints over time and received more biologics; they did not have worse outcomes related to axSpA in terms of activity and severity.

TRIAL REGISTRATION NUMBER

NCT01648907.

Australian Consensus Statements for the Assessment and Management of Non-radiographic Axial Spondyloarthritis

Background

The understanding of non-radiographic axial spondyloarthritis (nr-axSpA) has accelerated over the last decade, producing a number of practice-changing developments. Diagnosis is challenging. No diagnostic criteria exist, no single finding is diagnostic, and other causes of back pain may act as confounders.

Aim

To update and expand the 2014 consensus statement on the investigation and management of non‐radiographic axial spondyloarthritis (nr-axSpA).

Methods

We created search questions based on our previous statements and four new topics then searched the MEDLINE and Cochrane databases. We assessed relevant publications by full-text review and rated their level of evidence using the GRADE system. We compiled a GRADE evidence summary then produced and voted on consensus statements.

Results

We identified 5145 relevant publications, full-text reviewed 504, and included 176 in the evidence summary. We developed and voted on 22 consensus statements. All had high agreement. Diagnosis of nr-axSpA should be made by experienced clinicians, considering clinical features of spondyloarthritis, blood tests, and imaging. History and examination should also assess alternative causes of back pain and related conditions including non-specific back pain and fibromyalgia. Initial investigations should include CRP, HLA-B27, and AP pelvic radiography. Further imaging by T1 and STIR MRI of the sacroiliac joints is useful if radiography does not show definite changes. MRI provides moderate-to-high sensitivity and high specificity for nr-axSpA. Acute signs of sacroiliitis on MRI are not specific and have been observed in the absence of spondyloarthritis. Initial management should involve NSAIDs and a regular exercise program, while TNF and IL-17 inhibitors can be used for high disease activity unresponsive to these interventions. Goals of treatment include improving the frequent impairment of social and occupational function that occurs in nr-axSpA.

Conclusions

We provide 22 evidence-based consensus statements to provide practical guidance in the assessment and management of nr-axSpA.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40744-021-00416-7.

Peripheral disease contributes significantly to the level of disease activity in axial spondyloarthritis

Objective

Spondyloarthritis (SpA) can encompass axial, peripheral and extra-articular disease manifestations. Patients are classified as axial or peripheral SpA depending on the presence or absence of current back pain, independently of the other disease manifestations. Therefore, we aimed to assess the percentage of patients with axial SpA with peripheral disease and how this peripheral disease contributes to the overall disease activity.

Methods

Prevalence and disease activity of peripheral disease manifestations were assessed in a real-life observational cohort of 314 patients with the clinical diagnosis of SpA and fulfilling the Assessment of SpondyloArthritis international Society (ASAS) criteria.

Results

Of the 314 patients fulfilling the ASAS criteria, 230 fulfilled the axial and 84 the peripheral SpA criteria. Of the 230 patients with axial SpA, 49% had purely axial disease without peripheral disease manifestations whereas 51% had combined axial (back pain) and peripheral (arthritis, enthesitis and/or dactylitis) disease. The latter group had the highest disease activity in comparison with pure axial SpA as well as with peripheral SpA.

Conclusion

Half of the patients classified as axial SpA according to the ASAS criteria also have peripheral disease manifestations such as arthritis, enthesitis and/or dactylitis. These peripheral disease manifestations contribute significantly to overall disease activity.

Red flags for appropriate referral to the gastroenterologist and the rheumatologist of patients with inflammatory bowel disease and spondyloarthritis

Collaboration between gastroenterologists and rheumatologists is recommended for the correct management of patients with associated spondyloarthritis (SpA) and inflammatory bowel disease (IBD). We aimed to establish the appropriateness of several red flags for a prompt specialist referral. A systematic review of the literature was performed using the GRADE method to describe the prevalence of co-existing IBD-SpA and the diagnostic accuracy of red flags proposed by a steering committee. Then, a consensus among expert gastroenterologists and rheumatologists (10 in the steering committee and 13 in the expert panel) was obtained using the RAND method to confirm the appropriateness of each red flag as 'major' (one sufficient for patient referral) or 'minor' (at least three needed for patient referral) criteria for specialist referral. The review of the literature confirmed the high prevalence of co-existing IBD-SpA. Positive and negative predictive values of red flags were not calculated, given the lack of available data. A consensus among gastroenterology and rheumatology specialists was used to confirm the appropriateness of each red flag. Major criteria to refer patients with SpA to the gastroenterologist included: rectal bleeding, chronic abdominal pain, perianal fistula or abscess, chronic diarrhoea and nocturnal symptoms. Major criteria to refer patients with IBD to the rheumatologist included: chronic low back pain, dactylitis, enthesitis and pain/swelling of peripheral joints. Several major and minor red flags have been identified for the diagnosis of co-existing IBD-SpA. The use of red flags in routine clinical practice may avoid diagnostic delay and reduce clinic overload.

Ankylosing spondylitis and axial spondyloarthritis: recent insights and impact of new classification criteria

Development of the Assessment in Spondyloarthritis International Society (ASAS) classification criteria for axial spondyloarthritis (SpA) was one of the major breakthroughs in the field over the past decade. Despite some concerns related to the specificity of the criteria, they stimulated research into the early stage of the disease. This resulted in major advances in the understanding of the course of the disease, revealing predictors of progression, improvement in early diagnosis and treatment in axial SpA. In this review, we summarize the recent developments resulting from the introduction of the ASAS classification criteria for axial SpA and the implications for research and clinical practice.

The performance of classification criteria for juvenile spondyloarthropathies

Juvenile spondyloarthropathies (JSpA) are a group of rheumatologic diseases with a disease onset before 16; characterized with enthesitis, lower extremity oligoarthritis, involvement of the axial skeleton and HLA B27 positivity. The diversity of classification criteria along with the phenotype heterogeneity makes the classification of JSpA challenging. The aim of our study was to evaluate the performance of the pre-determined and recently proposed classification criteria for JSpA. The study group consisted of 113 patients with JSpA and 150 patients with juvenile idiopathic arthritis (JIA). Eligible criteria for JSpA were applied to all of the enrolled patients. The analysis of sensitivity, specificity and the kappa index were used to verify the performance of the JSpA criteria. The Amor criteria showed the highest sensitivity (98.2%) while the ASAS criteria for the axial SpA had highest specificity (100%). The sensitivity and specificity of the remaining criteria were: 93.8 and 63.8% for ESSG, 95.6 and 62.7% for Garmisch-Partenkirchen, 91.2 and 75.3% for ASAS criteria for peripheral SpA, respectively. Criteria proposed by our group showed the high sensitivity, specificity and kappa value: 90.3, 90.7, 0.843%, respectively. We suggest that criteria proposed by us could be used in the classification of JSpA. However, neither the pre-determined nor the new criteria are totally adequate and efficacious for the classification and diagnosis of this disease. The evaluation of the validity and reliability of proposed criteria in multicentric studies are mandatory, to increase its utility in routine clinical practice.

Clinical and Imaging Signs of Spondyloarthritis in First-Degree Relatives of HLA-B27-Positive Ankylosing Spondylitis Patients: The Pre-Spondyloarthritis (Pre-SpA) Cohort Study

OBJECTIVE

To investigate whether seemingly healthy first-degree relatives of patients with ankylosing spondylitis (AS) have clinical, laboratory, or imaging features of spondyloarthritis (SpA).

METHODS

First-degree relatives (ages 18-40 years) of HLA-B27-positive AS patients were included in the pre-spondyloarthritis (Pre-SpA) cohort, a prospective inception cohort study. Clinical, biologic, and imaging features were recorded. First-degree relatives were classified according to several sets of SpA classification criteria.

RESULTS

We report baseline features of 51 first-degree relatives included in this study. Twenty-nine (57%) had back pain, 2 (4%) had psoriasis, 1 (2%) had inflammatory bowel disease, and 1 (2%) had uveitis. Three (6%) had low-grade sacroiliitis, 1 (2%) had cervical syndesmophytes on radiography, and 10 (20%) had bone marrow edema on magnetic resonance imaging of the sacroiliiac joints. Seventeen of 51 first-degree relatives (33%) fulfilled SpA classification criteria: 7 (14%) fulfilled both Assessment of SpondyloArthritis international Society (ASAS) axial SpA and European Spondylarthropathy Study Group (ESSG) classification criteria, 6 (12%) fulfilled only ASAS axial SpA classification criteria, and 4 (8%) fulfilled only ESSG classification criteria; 3 (6%) also fulfilled the Amor criteria. None fulfilled other SpA classification criteria. First-degree relatives fulfilling the ASAS axial SpA and/or ESSG classification criteria had more frequent inflammatory back pain, had a higher level of disease activity, and had more psoriasis. No differences were found in parameters of inflammation, peripheral and extraarticular disease other than psoriasis, and HLA-B27 positivity between those who did and those who did not fulfill the ASAS axial SpA and/or ESSG classification criteria. Four first-degree relatives (12%) who did not fulfill the ASAS axial SpA and/or ESSG classification criteria had imaging abnormalities suggestive of SpA.

CONCLUSION

A substantial proportion of seemingly healthy first-degree relatives of HLA-B27-positive AS patients have clinical and/or imaging abnormalities suggestive of SpA. Thirty-three percent could be classified as having SpA. Further follow-up will show which first-degree relatives will develop clinically manifest SpA.

Axial spondyloarthritis

The term axial spondyloarthritis covers both patients with non-radiographic and radiographic axial spondyloarthritis, which is also termed ankylosing spondylitis. The disease usually starts in the third decade of life with a male to female ratio of two to one for radiographic axial spondyloarthritis and of one to one for non-radiographic axial spondyloarthritis. More than 90% heritabilty has been estimated, the highest genetic association being with HLA-B27. The pathogenic role of HLA-B27 is still not clear although various hypotheses are available. On the basis of evidence from trials the cytokines tumour necrosis factor (TNF)-α and interleukin-17 appear to have a relevant role in pathogenesis. The mechanisms of interaction between inflammation and new bone formation is still not completely understood but clarification will be important for the prevention of long-term structural damage of the bone. The development of new criteria for classification and for screening of patients with axial spondyloarthritis have been crucial for the early indentification and treatment of such patients, with MRI being the most important existing imaging method. Non-steroidal anti-inflammatory drugs and TNF blockers are effective therapies. Blockade of interleukin-17 is a new and relevant treatment option.

Polymorphisms of human leukocyte antigen B*27 on clinical phenotype of spondyloarthritis in Chinese

BACKGROUND

In recent years, an ever-increasing number of alleles of human leukocyte antigen B*27 (HLA-B*27) have been identified. This study aimed to establish an updated method for HLA-B*27 subtyping, and to investigate the impact of HLA-B*27 polymorphisms on the clinical phenotype of spondyloarthritis (SpA).

METHODS

Overall, 184 SpA patients were recruited for analyzing diversity of HLA-B*27 via an updated high-resolution polymerase chain reaction amplification with sequence specific primers (PCR-SSP).

RESULTS

The prevalence of HLA-B*27 was 94.0%, and four subtypes were identified including HLA-B*2704 (77.5%), B*2705 (20.2%), B*2707 (1.7%), and B*2724 (0.6%). There was an obvious male predominance (P=.05) and markedly elevated C-reaction protein (CRP) in B*27 positive SpA (P<.01). In multivariate linear regression analysis, the elevated CRP was positively associated with HLA-B*27 positivity (regression coefficient B=46.1, P=.0003), grade of sacroiliitis (B=47.5, P=.0032), and male gender (B=20.4, P=.0041). Notably, a male predilection was also found in B*2705 positive SpA while B*2707 was associated with older age, higher positive family history, and higher prevalence of extra-articular features (all P<.05).

CONCLUSIONS

In this study, an updated PCR-SSP technique to identify increasing alleles of HLA-B*27 was developed and their different effects on clinical manifestations of SpA were demonstrated. Genotyping of HLA-B*27 would shed light on our understanding of the pathogenesis of SpA.

Performance of the ASAS classification criteria for axial and peripheral spondyloarthritis: a systematic literature review and meta-analysis

Objective

To summarise the evidence on the performance of the Assessment of SpondyloArthritis international Society (ASAS) classification criteria for axial spondyloarthritis (axSpA) (also imaging and clinical arm separately), peripheral (p)SpA and the entire set, when tested against the rheumatologist's diagnosis (‘reference standard’).

Methods

A systematic literature review was performed to identify eligible studies. Raw data on SpA diagnosis and classification were extracted or, if necessary, obtained from the authors of the selected publications. A meta-analysis was performed to obtain pooled estimates for sensitivity, specificity, positive and negative likelihood ratios, by fitting random effects models.

Results

Nine papers fulfilled the inclusion criteria (N=5739 patients). The entire set of the ASAS SpA criteria yielded a high pooled sensitivity (73%) and specificity (88%). Similarly, good results were found for the axSpA criteria (sensitivity: 82%; specificity: 88%). Splitting the axSpA criteria in ‘imaging arm only’ and ‘clinical arm only’ resulted in much lower sensitivity (30% and 23% respectively), but very high specificity was retained (97% and 94% respectively). The pSpA criteria were less often tested than the axSpA criteria and showed a similarly high pooled specificity (87%) but lower sensitivity (63%).

Conclusions

Accumulated evidence from studies with more than 5500 patients confirms the good performance of the various ASAS SpA criteria as tested against the rheumatologist's diagnosis.

Predictive validity of the ASAS classification criteria for axial and peripheral spondyloarthritis after follow-up in the ASAS cohort: a final analysis

Objective

To establish the predictive validity of the Assessment of SpondyloArthritis international Society (ASAS) spondyloarthritis (SpA) classification criteria.

Methods

22 centres (N=909 patients) from the initial 29 ASAS centres (N=975) participated in the ASAS-cohort follow-up study. Patients had either chronic (>3 months) back pain of unknown origin and age of onset below 45 years (N=658) or peripheral arthritis and/or enthesitis and/or dactylitis (N=251). At follow-up, information was obtained at a clinic visit or by telephone. The positive predictive value (PPV) of the baseline classification by the ASAS criteria was calculated using rheumatologist's diagnosis at follow-up as external standard.

Results

In total, 564 patients were assessed at follow-up (345 visits; 219 telephone) with a mean follow-up of 4.4 years (range: 1.9; 6.8) and 70.2% received a SpA diagnosis by the rheumatologist. 335 patients fulfilled the axial SpA (axSpA) or peripheral SpA (pSpA) criteria at baseline and of these, 309 were diagnosed SpA after follow-up (PPV SpA criteria: 92.2%). The PPV of the axSpA and pSpA criteria was 93.3% and 89.5%, respectively. The PPV for the ‘clinical arm only’ was 88.0% and for the ‘clinical arm’±‘imaging arm’ 96.0%, for the ‘imaging arm only’ 86.2% and for the ‘imaging arm’+/-‘clinical arm’ 94.7%. A series of sensitivity analyses yielded similar results (range: 85.1–98.2%).

Conclusions

The PPV of the axSpA and pSpA criteria to forecast an expert's diagnosis of ‘SpA’ after more than 4 years is excellent. The ‘imaging arm’ and ‘clinical arm’ of the axSpA criteria have similar predictive validity and are truly complementary.

Evaluation of the impact of fibromyalgia in disease activity and treatment effect in spondyloarthritis

BACKGROUND

Fibromyalgia (FM) can coexist with Spondyloarthritis (SpA) leading to diagnostic and treatment dilemmas, especially in the presence of enthesitis. With this study we aimed to estimate the prevalence of FM in SpA and to compare the clinical/disease features and TNF inhibitors (TNFi) in patients with/without FM.

METHOD

FM was defined by a score = > 5/6 of the Fibromyalgia Rapid Screening Tool (FiRST). SpA patients (according to the rheumatologist) and consecutively consulting in the day care hospital but also in the outpatient clinic at the rheumatology department of a tertiary care university hospital were included. Demographics, disease characteristics, activity and severity and TNFi treatment were compared in patients with and without FM; retention rate of the first TNFi and associated factors were explored (Kaplan Meier and Cox regression).

RESULTS

Of the 196 enrolled SpA patients, 42 (21.4 %) were positively screened for FM. No statistically significant differences in the prevalence of FM were found with regard to the fulfillment of the ASAS criteria for peripheral/axial SpA, nor with regard to the fulfillment of the imaging vs. clinical arm of the ASAS criteria. However, patients with coexisting FM presented significantly with more enthesitis, higher disease activity (BASDAI and VAS) and poorer function scores (BASFI). No differences were found with regard to the initiation of TNFi treatment (79.0 % vs. 70.0 %, respectively), but the retention rate of the first TNFi after 2 years was shorter in the group of patients with FM (28.1 % (95 % CI 12.5-44.0) vs. 41.7 % (95 % CI 32.2-51.3), p = 0.01).

CONCLUSION

This study confirms that coexistent FM in SpA might impact the patient-reported outcome indices for disease activity and function, and the retention rate of TNFi treatment.

Analysis and performance of various classification criteria sets in a Colombian cohort of patients with spondyloarthritis

The objective of this study was to investigate the performance of classification criteria sets (Assessment of SpondyloArthritis international Society (ASAS), European Spondylarthropathy Study Group (ESSG), and Amor) for spondyloarthritis (SpA) in a clinical practice cohort in Colombia and provide insight into how rheumatologists follow the diagnostic path in patients suspected of SpA. Patients with a rheumatologist's diagnosis of SpA were retrospectively classified according to three criteria sets. Classification rate was defined as the proportion of patients fulfilling a particular criterion. Characteristics of patients fulfilling and not fulfilling each criterion were compared. The ASAS criteria classified 81 % of all patients (n = 581) as having either axial SpA (44 %) or peripheral SpA (37 %), whereas a lower proportion met ESSG criteria (74 %) and Amor criteria (53 %). There was a high degree of overlap among the different criteria, and 42 % of the patients met all three criteria. Patients fulfilling all three criteria sets were older (36 vs. 30 years), had more SpA features (3 vs. 1 features), and more frequently had a current or past history of back pain (77 vs. 43 %), inflammatory back pain (47 vs. 13 %), enthesitis (67 vs. 26 %), and buttock pain (37 vs. 13 %) vs. those not fulfilling any criteria. HLA-B27, radiographs, and MRI-SI were performed in 77, 59, and 24 % of the patients, respectively. The ASAS criteria classified more patients as having SpA in this Colombian cohort when the rheumatologist's diagnosis is used as an external standard. Although physicians do not perform HLA-B27 or imaging in all patients, they do require these tests if the clinical symptoms fall short of confirming SpA and suspicion remains.

The prevalence of axial spondyloarthritis in the UK: a cross-sectional cohort study

Background

Accurate prevalence data are important when interpreting diagnostic tests and planning for the health needs of a population, yet no such data exist for axial spondyloarthritis (axSpA) in the UK. In this cross-sectional cohort study we aimed to estimate the prevalence of axSpA in a UK primary care population.

Methods

A validated self-completed questionnaire was used to screen primary care patients with low back pain for inflammatory back pain (IBP). Patients with a verifiable pre-existing diagnosis of axSpA were included as positive cases. All other patients meeting the Assessment of SpondyloArthritis international Society (ASAS) IBP criteria were invited to undergo further assessment including MRI scanning, allowing classification according to the European Spondyloarthropathy Study Group (ESSG) and ASAS axSpA criteria, and the modified New York (mNY) criteria for ankylosing spondylitis (AS).

Results

Of 978 questionnaires sent to potential participants 505 were returned (response rate 51.6 %). Six subjects had a prior diagnosis of axSpA, 4 of whom met mNY criteria. Thirty eight of 75 subjects meeting ASAS IBP criteria attended review (mean age 53.5 years, 37 % male). The number of subjects satisfying classification criteria was 23 for ESSG, 3 for ASAS (2 clinical, 1 radiological) and 1 for mNY criteria. This equates to a prevalence of 5.3 % (95 % CI 4.0, 6.8) using ESSG, 1.3 % (95 % CI 0.8, 2.3) using ASAS, 0.66 % (95 % CI 0.28, 1.3) using mNY criteria in chronic back pain patients, and 1.2 % (95 % CI 0.9, 1.4) using ESSG, 0.3 % (95 % CI 0.13, 0.48) using ASAS, 0.15 % (95 % CI 0.02, 0.27) using mNY criteria in the general adult primary care population.

Conclusions

These are the first prevalence estimates for axSpA in the UK, and will be of importance in planning for the future healthcare needs of this population.

Trial registration

Current Controlled Trials ISRCTN76873217