MRI of sacroiliac joints for the diagnosis of axial SpA: prevalence of inflammatory and structural lesions in nulliparous, early postpartum and late postpartum women

Annals of the Rheumatic Diseases collection on pregnancy 2018-2023: observational data-driven knowledge

Pregnancy can be an exciting time but for those living with rheumatic musculoskeletal diseases (RMDs), it can also be a time fraught with concern, including what effect pregnancy will have on the underlying RMD and what effect the RMD may have on the pregnancy and the baby, including the effects of medications. Generating an evidence base in pregnancy is challenging. Few interventional trials of medications in RMD pregnancies have ever been conducted, often for concerns of safety for both the mother and the child. Therefore, observational research remains important for informing clinical practice and helping women with RMDs make decisions regarding their health preconception and during pregnancy. The Annals of the Rheumatic Diseases (ARD) continues to publish important research on pregnancy in RMDs to increase the evidence base on this subject. Here we present an overview of papers published on this topic between January 2018 and December 2023. Our focus includes papers on pregnancy and RMD outcome, the effects of drug exposure, fetal outcomes as well as fertility.

Magnetic Resonance Imaging Topography of Bone Marrow Edema in the Sacroiliac Joint of Postpartum Women

OBJECTIVE

A traditional monoplanar semicoronal and a biplanar magnetic resonance imaging (MRI) assessment method were used to compare the topographical distribution of postpartum strain-related bone marrow edema (BME) at the sacroiliac joint (SIJ).

METHODS

The presence and topographical location of SIJ BME were assessed independently by three readers in 71 women 12 months postpartum. A traditional monoplanar semicoronal and a biplanar BME evaluation by 8 (upper and lower) and 12 joint (upper, middle, and lower) regions, respectively, was performed with >4 weeks between the two assessments. Descriptive results were reported as mean ± SD and ranges, and interreader agreement by intraclass correlation coefficient (ICC).

RESULTS

By semicoronal assessment, 38 (53.5%) women had BME with a mean ± SD SPARCC score of 2.3 ± 4.0 (range 0-22; ICC 0.93, 95% confidence interval [CI] 0.92-0.94). Forty-one (57.8%) had BME by biplanar assessment with a mean ± SD sum score of 2.9 ± 5.8 (range 0-32.7; ICC 0.89, 95% CI 0.88-0.91). By semicoronal assessment, the highest frequency and mean SPARCC scores were in the anterior upper regions of ilium (24%, mean 0.6) and sacrum (21%, mean 0.3) followed by the posterior upper sacral (20%, mean 0.4) and posterior lower iliac (20%, mean 0.3) regions. By biplanar assessment, the anterior middle joint regions had highest BME frequency and sum scores, sacral side (32%, mean 1.9) and iliac side (27%, mean 2.0), respectively; frequencies and sum scores were generally higher in the anterior compared to the posterior joint regions.

CONCLUSION

The 12-region biplanar assessment revealed a predominantly anterior middle location of postpartum SIJ BME whereas the 8-region monoplanar approach did not demarcate distinct strain-prone SIJ regions. Complementing traditional monoplanar semicoronal SIJ MRI evaluation by a semiaxial assessment may facilitate discrimination of strain-related conditions from early axial spondyloarthritis.

Prognostic value of the clinical and imaging arm of the ASAS criteria for progression of structural sacroiliac joint lesions

OBJECTIVE

To investigate the prognostic value of the two arms of the Assessment of SpondyloArthritis international Society (ASAS) criteria regarding the progression of structural lesions in the sacroiliac joints (SIJs).

METHODS

Information on baseline fulfilment of the ASAS criteria and baseline and follow-up magnetic resonance imaging of the SIJ in 603 patients aged 18-40 years referred with low back pain to an outpatient spine were collected. Magnetic resonance imaging positivity was defined as bone marrow oedema (BMO) in two or more consecutive slices or two or more lesions in one slice, as described in the ASAS definition of sacroiliitis.

RESULTS

Of 71 participants fulfilling the ASAS criteria at baseline, 66 (93%) fulfilled the 'imaging arm' and 14 (20%) fulfilled the 'clinical arm'. The 'clinical arm' predicted the progression of erosions with an odds ratio of 55 (compared with not fulfilling the ASAS criteria), while the 'imaging arm' predicted the progression of erosions with an odds ratio of 8. Moreover, in 24% of the patients in the 'imaging arm', all having BMO at the SIJ at baseline, the BMO disappeared without neither erosions nor ankylosis emerging.

CONCLUSION

We found that the 'clinical arm' was a strong predictor for the progression of SIJ erosion, while the 'imaging arm' had a more modest prognostic value for structural progression.

Sacroiliac joint MRI for diagnosis of ax-SpA: algorithm to improve the specificity of the current ASAS MRI criteria

OBJECTIVE

To compare sacroiliac joint (SIJ) lesions on MRI in women with versus without axial spondyloarthritis (ax-SpA) and establish an algorithm to determine whether such lesions are due to ax-SpA.

METHODS

This retrospective comparative study assessed bone marrow edema (BME), sclerosis, erosions, osteophytes, and ankylosis at the SIJ in two groups of women, one with and another without ax-SpA. Sensitivity and specificity were calculated for combinations/characteristics of lesions, using rheumatologists' assessment with assessment of spondyloarthritis international society (ASAS) criteria as the gold standard for diagnosis of ax-SpA.

RESULTS

Compared to women without ax-SpA, women with ax-SpA had more BME (61% vs 17%, p < 0.001), sclerosis (40% vs 22%, p < 0.001), erosions (35% vs 5%, p < 0.001), and ankylosis (2% vs 0%, p = 0.007), but less osteophytes (5% vs 33%, p < 0.001). The ASAS MRI criteria yielded 59% sensitivity and 88% specificity, while a new algorithm achieved 56% sensitivity and 95% specificity using the following criteria: no osteophytes at the SIJ and either (i) BME at the SIJ with at least one dimension ≥ 8 mm or (ii) at least one erosion at the SIJ.

CONCLUSIONS

We recommend the following pragmatic algorithm for MRI diagnosis of ax-SpA in women: no osteophytes at the SIJ and either (i) BME at the SIJ with at least one dimension ≥ 8 mm or (ii) at least one erosion at the SIJ. The false positive rate when using the new algorithm (3.3%) is less than half than when using the ASAS MRI criteria (7.7%); thus, its application in clinical practice could reduce overdiagnosis and prevent overtreatment of ax-SpA.

CLINICAL RELEVANCE STATEMENT

The developed algorithm has a false-positive rate that is less than half than when using the ASAS MRI criteria (3.3% vs 7.7%), thus its application in clinical practice could reduce overdiagnosis and prevent overtreatment of axial spondyloarthritis.

KEY POINTS

• Compared to women without axial spondyloarthritis (ax-SpA), women with ax-SpA had a significantly higher prevalence of bone marrow edema (BME), sclerosis, erosions, and ankylosis, but a significantly lower prevalence of osteophytes. • A new algorithm for positive ax-SpA based on sacroiliac joint MRI was developed: no osteophytes at the sacroiliac joint (SIJ) and either (i) BME at the SIJ with at least one dimension ≥ 8 mm or (ii) at least one erosion at the SIJ. • We recommend this new algorithm for diagnosis of ax-SpA in women, as it has a significantly better specificity than the assessment of spondyloarthritis international society (ASAS) MRI criteria and less than half the false positive rate; thus, its application in clinical practice could reduce overdiagnosis and prevent overtreatment of ax-SpA.

Artificial intelligence for the detection of sacroiliitis on magnetic resonance imaging in patients with axial spondyloarthritis

Background

Magnetic resonance imaging (MRI) is important for the early detection of axial spondyloarthritis (axSpA). We developed an artificial intelligence (AI) model for detecting sacroiliitis in patients with axSpA using MRI.

Methods

This study included MRI examinations of patients who underwent semi-coronal MRI scans of the sacroiliac joints owing to chronic back pain with short tau inversion recovery (STIR) sequences between January 2010 and December 2021. Sacroiliitis was defined as a positive MRI finding according to the ASAS classification criteria for axSpA. We developed a two-stage framework. First, the Faster R-CNN network extracted regions of interest (ROIs) to localize the sacroiliac joints. Maximum intensity projection (MIP) of three consecutive slices was used to mimic the reading of two adjacent slices. Second, the VGG-19 network determined the presence of sacroiliitis in localized ROIs. We augmented the positive dataset six-fold. The sacroiliitis classification performance was measured using the sensitivity, specificity, and area under the receiver operating characteristic curve (AUROC). The prediction models were evaluated using three-round three-fold cross-validation.

Results

A total of 296 participants with 4,746 MRI slices were included in the study. Sacroiliitis was identified in 864 MRI slices of 119 participants. The mean sensitivity, specificity, and AUROC for the detection of sacroiliitis were 0.725 (95% CI, 0.705-0.745), 0.936 (95% CI, 0.924-0.947), and 0.830 (95%CI, 0.792-0.868), respectively, at the image level and 0.947 (95% CI, 0.912-0.982), 0.691 (95% CI, 0.603-0.779), and 0.816 (95% CI, 0.776-0.856), respectively, at the patient level. In the original model, without using MIP and dataset augmentation, the mean sensitivity, specificity, and AUROC were 0.517 (95% CI, 0.493-0.780), 0.944 (95% CI, 0.933-0.955), and 0.731 (95% CI, 0.681-0.780), respectively, at the image level and 0.806 (95% CI, 0.729-0.883), 0.617 (95% CI, 0.523-0.711), and 0.711 (95% CI, 0.660-0.763), respectively, at the patient level. The performance was improved by MIP techniques and data augmentation.

Conclusion

An AI model was developed for the detection of sacroiliitis using MRI, compatible with the ASAS criteria for axSpA, with the potential to aid MRI application in a wider clinical setting.

Sex-specific diagnostic efficacy of MRI in axial spondyloarthritis: challenging the 'One Size Fits All' notion

OBJECTIVES

Sex-specific differences in the presentation of axial spondyloarthritis (axSpA) may contribute to a diagnostic delay in women. The aim of this study was to investigate the diagnostic performance of MRI findings comparing men and women.

METHODS

Patients with back pain from six different prospective cohorts (n=1194) were screened for inclusion in this post hoc analysis. Two blinded readers scored the MRI data sets independently for the presence of ankylosis, erosion, sclerosis, fat metaplasia and bone marrow oedema. Χ2 tests were performed to compare lesion frequencies. Contingency tables were used to calculate markers for diagnostic performance, with clinical diagnosis as the standard of reference. The positive and negative likelihood ratios (LR+/LR-) were used to calculate the diagnostic OR (DOR) to assess the diagnostic performance.

RESULTS

After application of exclusion criteria, 526 patients (379 axSpA (136 women and 243 men) and 147 controls with chronic low back pain) were included. No major sex-specific differences in the diagnostic performance were shown for bone marrow oedema (DOR m: 3.0; f: 3.9). Fat metaplasia showed a better diagnostic performance in men (DOR 37.9) than in women (DOR 5.0). Lower specificity was seen in women for erosions (77% vs 87%), sclerosis (44% vs 66%), fat metaplasia (87% vs 96%).

CONCLUSION

The diagnostic performance of structural MRI markers is substantially lower in female patients with axSpA; active inflammatory lesions show comparable performance in both sexes, while still overall inferior to structural markers. This leads to a comparably higher risk of false positive findings in women.

HLA-B27 status and inflammatory MRI lesions of the sacroiliac joints: a post hoc analysis in patients without axial spondyloarthritis

OBJECTIVE

The assessment of inflammatory and structural lesions in the sacroiliac joint (SIJ) is crucial in axial spondyloarthritis (axSpA). HLA-B27 status plays an important role in axSpA diagnosis and has been linked to MRI lesion burden in the general population. We aimed to investigate the sex-specific influence of HLA-B27 status on inflammatory and structural MRI findings in patients with low back pain of non-inflammatory origin.

METHODS

This post hoc analysis included 139 non-axSpA patients (90 women) with chronic low back pain. Two readers scored MRIs of the SIJ for the presence of sclerosis, erosion, fat metaplasia, bone marrow oedema (BMO) and ankylosis. Frequencies and extent of lesions were compared regarding the HLA-B27 status using χ2 tests and t-tests. Regression models to assess the sex-dependent influence of HLA-B27 on lesion burden were computed.

RESULTS

HLA-B27 was positive in 33 women (36.7%) and 23 men (46.9%). The overall occurrence of all SIJ lesions did not differ in HLA-B27 negative and positive individuals. There were no significant differences in the extent of lesions considering the HLA-B27 positivity, for erosion (mean sum score (MSS) of 0.91 vs 0.48; p=0.144), sclerosis (MSS 1.65 vs 1.88; p=0.576), fat metaplasia (MSS 0.56 vs 0.27; p=0.425), BMO (MSS 0.75 vs 0.59; p=0.460) and ankylosis (MSS 0.06 vs 0.04; p=0.659).

CONCLUSION

HLA-B27 status has no significant influence on the occurrence and extent of SIJ lesions in patients with low back pain of non-inflammatory origin in either men or women.

Sex Disparities of the Sacroiliac Joint: Focus on Joint Anatomy and Imaging Appearance

The sacroiliac joint (SIJ) is an anatomically complex joint which, as a functional unit with the pelvis and spine, is of decisive biomechanical importance for the human body. It is also a commonly overlooked source of lower back pain. Like the entire bony pelvis, the SIJ exhibits major sexual dimorphisms; thus, the sex-dependent evaluation of this joint is becoming increasingly important in clinical practice, both anatomically with joint shape variations and biomechanical differences as well as in terms of image appearance. The influence of the SIJ shape, which differs in women and men, is crucial for the different biomechanical joint properties. These differences are important in the development of joint diseases at the SIJ, which shows a specific difference between the sexes. This article aims to provide an overview of sex disparities of the SIJ regarding different anatomical and imaging appearances to further understand the insights into the interplay of sex differences and SIJ disease.

Back pain and assessment of ankylosing spondylitis activity during gestation: symptoms reflecting exacerbation of the disease and pregnancy

Objective: to study the dynamics of back pain severity and the frequency of its individual components, characterizing the inflammatory and mechanical rhythm, on the background of gestation in women with ankylosing spondylitis (AS) and compare them with manifestations of dorsopathy in healthy pregnant women; to determine the information value of BASDAI during pregnancy, i.e. to identify its components with the optimal sensitivity and specificity ratio for assessing AS activity during gestation.

Patients and methods. The main group consisted of 49 pregnant women with AS who met the modified New York criteria of 1984. The average age of patients was 31.7±4.9 years, the average duration of the disease was 134.4±85.8 months. BASDAI for trimesters of pregnancy was: 2.3 [1.2; 4.4], 2.8 [1.4; 4.2] and 2.2 [1.6; 4.0]. The control group included 51 pregnant women with back pain associated with gestation, without rheumatic diseases. The average age was 28.0±4.4 years. The intensity of back pain was assessed on a numerical rating scale. ROC-analysis was performed with calculation of the area under the curve (AUC) of each component of BASDAI in each pregnancy trimester.

Results and discussion. More than 80% of pregnant women with AS experienced back pain, while the intensity of general back pain did not differ from that in the control group. Night back pain with improvement on awakening in the main group was present in 70%, 58% and 68.8% of women, respectively, in the I-III trimesters; its intensity was 3 [1; 5], 3.5 [3; 6] and 3.4 [2; 5] respectively; the frequency and severity of night pain were higher than in the control group. The number of women with improvement after exercise in the II and III trimesters did not differ in both groups. In the second half of pregnancy, 40% of AS patients noted improvement during rest, 52.1% – increased pain after exercise; the frequency of mechanical rhythm pain elements remained lower than in the control group. The AUC value for BASDAI in the first trimester was 0.74; AUC of all BASDAI components was >0.5. In the II and III trimesters, the AUC values for fatigue and back pain were 0.8.

Conclusion. During pregnancy the vast majority of women with AS experience back pain, the nature of which changes in the second half of gestation. Night pain that improves on awakening reflects AS activity and is not related to pregnancy. The BASDAI components of severity and duration of morning stiffness have the highest classification value during pregnancy.

 

A glance into the future of diagnosis and treatment of spondyloarthritis

The last two decades have seen major developments in the field of spondyloarthritis (SpA), but there are still important unmet needs to address. In the future, we envisage important advances in the diagnosis and treatment of SpA. In the diagnosis of SpA, the use of online and social media tools will increase awareness of the disease and facilitate the referral of patients to rheumatology clinics. In addition, more specific diagnostic tests will be available, especially advanced imaging methods and new biomarkers. This will allow most patients to be diagnosed at an early stage of the disease. In the treatment of SpA, an increasing number of novel treatment targets can be expected, most of which will be directed against intracellular enzymes. We hope to see more strategy trials shaping treatment pathways in SpA and accommodating principals of precision medicine. Approved treatment options will be available for both axial and peripheral SpA. We also hope to intervene not only at the inflammation level but also at the level of underlying immunological processes that might be associated with a higher probability of long-standing remission if not a cure. Finally, artificial intelligence techniques will allow for the analysis of large-scale data to answer relevant research questions for the diagnosis and management of patients with SpA.

Pregnancy-related sacroiliac joint findings in females with low back pain: a four-year magnetic resonance imaging follow-up study

BACKGROUND

Pregnancy-related pain may be associated with sacroiliac joint (SIJ) changes, detectable by magnetic resonance imaging (MRI).

PURPOSE

To analyze the prevalence and course of SIJ MRI and clinical findings in women referred with low back pain and relate these to pregnancy.

MATERIAL AND METHODS

A retrospective follow-up study from a longitudinally collected cohort comprising 328 women.

RESULTS

Women reporting debut of pain in relation to a pregnancy (PP group) tended to have a higher baseline prevalence of all investigated MRI findings, cumulated positive SIJ tests, and a potential fulfilment of the spondyloarthritis diagnosis compared to remainders. The prevalence of subchondral bone marrow edema (BME), any SIJ MRI finding, and potential fulfilment of the spondyloarthritis diagnosis were significantly higher in the PP group compared to women who had not been pregnant. In the total study group, the prevalence of ≥1 MRI finding increased over the four-year study period from 34% to 47% (P<0.001), driven by increasing prevalence of BME (25% to 32%; P=0.008) and fatty marrow deposition (FMD) (20% to 25%; P=0.020). In addition, the BME volume score increased. Over time, the PP group had persisting high prevalence of buttock pain and total MRI findings and their FMD volume score increased, but there were no between-group differences in MRI variables at follow-up.

CONCLUSION

Overall, the prevalence of MRI findings increased over time. Although the PP group had different clinical and SIJ MRI characteristics cross-sectional at baseline compared to remainders, longitudinal analyses revealed that these diminished over time.

Differences in topographical location of sacroiliac joint MRI lesions in patients with early axial spondyloarthritis and mechanical back pain

Background

Early diagnostics of axial spondyloarthritis (axSpA) remains a challenge. Traditional imaging one-plane sacroiliac joint (SIJ) MRI assessment is used. By introducing a two-plane assessment system, the objective was to analyse the differences in SIJ MRI changes in early axSpA compared with changes in patients with mechanical back pain (MBP) by exploring the differences in volume and location.

Methods

MRIs in the early diagnostic state of 25 axSpA patients (mean age 31.3 years) and 59 MBP patients (mean age 32.3 years) were included. The MRIs were assessed by two readers regarding the distribution of bone marrow edema (BME) in 14 joint portions and structural changes in six joint portions in addition to SIJ anatomical variations and lumbar spine disc degeneration.

Results

AxSpA patients had a significantly higher overall BME sumscore (volume) of 25.1 compared to MBP patients 6.8, p < 0.005. The MBP group had the highest prevalence (66%) and sumscore (5.7) in the middle anterior sacrum. The axSpA group had significantly higher prevalence and sumscores in all joint portions except the three cartilaginous anterior sacral joint portions, including the ligamentous compartments (prevalence 40–60% compared to 8–15%, p both < 0.005). The axSpA group had also a significantly higher prevalence of erosions and fatty marrow disposition, but there were no differences in the prevalence of anatomical variations except the bipartite iliac bony plate.

Conclusions

AxSpA patients demonstrated a widespread distribution of both inflammatory and structural changes, including high BME occurrence in the ligamentous joint portions whereas patients with MBP had the highest occurrence of BME in the middle anterior sacrum. These findings may help differentiate axSpA patients from other back pain conditions in the early diagnostic phase.

Managing puerperium in patients with systemic autoimmune diseases: an update

INTRODUCTION

Puerperium is a critical period for patients affected by autoimmune rheumatic diseases for the risk of disease's flares and difficulties in treating lactating mothers. We want to summarize the literature data about psychological and pharmacological management of these patients and possible risk factors of disease's flares.

AREAS COVERED

We made a narrative review on recent studies about puerperium in rheumatic autoimmune diseases patients.

EXPERT OPINION

The physicians involved in management of patients during puerperium and in the follow-up of babies need to agree on maternal treatment because they need to reassure mothers about the safety of the prescribed medications. Furthermore, women with rheumatic diseases could present some musculoskeletal limitations and psychological problems, such as postpartum depression, which can lead to a sense of inadequacy to the mother's task. Families and physicians should be aware of these possible complications and support the new mothers providing correct counseling and practical help.

Striking sex differences in magnetic resonance imaging findings in the sacroiliac joints in the population

Background

In patients with axial spondyloarthritis (axSpA), magnetic resonance imaging (MRI) is used to detect bone marrow edema (BME) in sacroiliac joints (SIJ) but SIJ BME are also detected in the population. Not much is known about sex differences in that regard.

Objective

To explore sex-specific differences associated with the extent of BME in the SIJ suggestive of axSpA in a general population cohort study.

Methods

Taking advantage of 793 recently evaluated MRIs of subjects < 45 years taking part in the SHIP cohort, we used negative-binomial (NB) count data regression to analyze factors associated with the extent of SIJ BME. Predictors were explored by model-based boosting (MBB), a machine learning approach.

Results

Estimates of NB regression showed strong effects of sex in interaction with age, BMI, back pain, and particularly HLA-B27. The NB regression model showed incidence rate ratios (IRR) for the main effect of sex (females vs. males): 0.94 [95% CI: 0.63; 1.41], HLA-B27: 4.32 [2.09; 9.8], and for the interaction of sex to HLA-B27: 0.22 [0.06; 0.75]. According to MBB, HLA-B27 positivity, BMI, current smoking, back pain in the last 3 months, the interaction of sex and HLA-B27, and delivery in the last 12 months were of highest importance to explain the extent of SIJ BME.

Conclusions

Different factors were associated with the extent of SIJ BME in females and males. Most importantly, HLA-B27 was relevant only in males but not in females in whom a postpartal state was important. This finding may be relevant for the pathogenesis of axSpA.

Sex-associated and gender-associated differences in the diagnosis and management of axial spondyloarthritis: addressing the unmet needs of female patients

Emerging evidence suggests that axial spondyloarthritis (axSpA) should not be seen as a predominantly male disease, as the non-radiographic form occurs with roughly equal frequency in women and men. However, men and women experience this disease differently. The purpose of this review is to highlight sex-associated and gender-associated differences in the patient's journey through the diagnosis and management of axSpA, in order to increase the awareness about the unmet needs of female axSpA patients.Female patients experience a longer diagnostic delay compared with men, possibly due to the different pattern of clinical presentations across genders. Therefore, it is crucial to sensitise physicians to pay attention and identify the red flags of axSpA in women and promote early referral to a rheumatologist. Women with a diagnosis of axSpA experience greater limitations in physical function, although they have less structural spinal damage compared with men. Women tend to have less adherence and a lower response to treatment, so more gender-oriented data are needed about drugs used for axSpA, especially biological disease-modifying antirheumatic drugs.Lifestyle factors have a strong impact on the disease course. Interventions regarding physical activity, smoking cessation and diet should be communicated to the patients, with particular attention to the gender-related cultural background.Patients of childbearing age living with axSpA should be engaged in a discussion about reproductive health, in terms of preservation of fertility, management of pregnancy and delivery and use of biologic drugs during pregnancy and breastfeeding.

Main Diagnostic Pitfalls in Reading the Sacroiliac Joints on MRI

Magnetic resonance imaging of the sacroiliac joints is now frequently performed to help identify patients with early axial spondyloarthritis. However, differential diagnoses exist and should be recognized. The aim of this article is to review the most frequent differential diagnoses that may mimic inflammatory sacroiliitis in clinical practice.

CT-like images of the sacroiliac joint generated from MRI using susceptibility-weighted imaging (SWI) in patients with axial spondyloarthritis

Background

To analyse the added value of susceptibility-weighted imaging (SWI) compared with standard T1-weighted (T1) MRI for detecting structural lesions of the sacroiliac joint (SIJ) in patients with axial spondyloarthritis (axSpA) using CT as reference standard.

Material and methods

Sixty-eight patients with suspected or proven axSpA underwent both MRI and CT of the SIJ on the same day. Two readers separately scored CT, T1 and SWI for the presence of erosions, sclerosis and joint space changes using an established 24-region SIJ model. Disagreement was resolved by a third reader. Diagnostic accuracy (McNemar test), Cohen’s kappa (k), sensitivity (SE) and specificity were calculated on the joint level using CT as reference.

Results

In CT, 38 joints showed erosions, 67 sclerosis and 37 joint space changes. Agreement with CT for erosions was 92.6% (k=0.811 (0.7–0.92)) in SWI and 87.5% (k=0.682 (0.54–0.82)) in T1 (p=0.143) and agreement for sclerosis 84.6% (k=0.69 (0.57–0.81)) and 62.5% (k=0.241 (0.13–0.35)) (p<0.001), respectively. This resulted in superior SE of SWI (81.6% vs 73.7%) for erosions and sclerosis (74.6% vs 23.9%) at a minor expense of SP. No differences were detected for joint space changes.

Conclusion

In patients with axSpA, SWI depicts erosions and sclerosis more accurately than T1 spin echo MRI at 1.5 T.

Imaging in Axial Spondyloarthritis: What is Relevant for Diagnosis in Daily Practice?

PURPOSE OF REVIEW

To explore how imaging may assist diagnosing axial spondyloarthritis in rheumatology practice.

RECENT FINDINGS

A diagnosis of axial spondyloarthritis is based on pattern recognition by synthesizing clinical, laboratory, and imaging findings. In health care settings providing low threshold access to advanced imaging, sacroiliac joint MRI is the preferred imaging modality in clinically suspected axial spondyloarthritis. In daily routine, the optimum protocol to assess suspected inflammatory back pain combines sacroiliac joint and spine MRI fitting a 30-min slot. Contextual assessment of concomitant structural and active MRI lesions is key to enhance diagnostic utility. In women with postpartum back pain suggestive of axial spondyloarthritis, recent reports advocate waiting 6-12 months after delivery before acquiring sacroiliac joint MRI. Major unmet needs are consistent MRI protocols, standardized training modules on how to evaluate axial MRI, and timely dissemination of imaging advances into mainstream practice both in rheumatology and in radiology. In rheumatology practice, MRI has become indispensable to help diagnose early axial spondyloarthritis. However, major gaps in training and knowledge transfer to daily care need to be closed.

Diagnostic delay in axial spondyloarthritis - a past or current problem?

PURPOSE OF REVIEW

To evaluate recent data on diagnostic delay in axial spondyloarthritis (axSpA), factors affecting the delay, potential ways of early diagnosis improvement, and risks associated with early diagnostic approaches.

RECENT FINDINGS

Although axSpA can be diagnosed nowadays within the first months after symptom onset, the diagnostic delay remains with several years still remarkably high in many parts of the world. Female gender, human leukocyte antigen-B27 negativity, and younger age at disease onset are among factors associated with a delayed referral to a rheumatologist and consequently with a larger diagnostic delay. Early referral algorithms are helpful in the identification of patients with a high probability of axSpA among patients with chronic back pain. A careful diagnostic evaluation with correct imaging interpretation is required to avoid misdiagnosis of axSpA in patients with unspecific back pain.

SUMMARY

The diagnostic delay is still considerable in axSpA. The ways to early diagnosis in axSpA are well defined. Imaging findings should always be considered in the clinical context to avoid axSpA misdiagnosis.

Morphological characteristics of sacroiliac joint MRI lesions in axial spondyloarthritis and control subjects

OBJECTIVES

To investigate sacroiliac joint(SIJ) MRI inflammation, structural and degenerative lesion characteristics in patients with axial spondyloarthritis(axSpA) and various control groups.

METHODS

Patients with axSpA(n = 41) and lumbar disc herniation(n = 25), women with(n = 46) and without(n = 14) post-partum(childbirth within 4-16 months) buttock/pelvic pain, cleaning assistants(n = 26), long-distance runners(n = 23) and healthy men(n = 29) had MRI of the SIJs prospectively performed. MRI lesions were assessed on 9 slices covering the cartilaginous compartment by two experienced readers according to the definitions of the Spondyloarthritis Research Consortium of Canada(SPARCC) SIJ inflammation and structural scores, and were evaluated according to depth and extent. Other morphological characteristics were also analysed.

RESULTS

Total depth scores for bone marrow oedema(BME) and fat lesion(FAT) and total extent score for erosion were statistically significantly highest in axSpA, while scores for sclerosis were numerically highest in women with post-partum pain. Maximum BME depth > 10mm was frequently and exclusively found in axSpA and post-partum women(39% vs 14-17%) while FAT depth > 5mm was predominantly found in axSpA(76% vs 0-10%). Erosions were primarily seen in axSpA, especially when extensive(≥4 or confluent; 17% vs 0%). Capsulitis was absent in non-axSpA groups. BME and FAT in the ligamentous compartment were primarily found in axSpA(17/22% vs 0/2% in non-axSpA groups). In non-axSpA, osteophytes(axSpA vs non-axSpA: 0% vs 3-17%) and vacuum phenomenon(7% vs 30-66%) were more frequent, and the joint space was wider(mean(SD) 1.5(0.9)mm vs 2.2(0.5)mm).

CONCLUSIONS

FAT depth > 5mm, but not BME depth > 10mm, could almost differentiate axSpA patients from all other groups. When excluding post-partum women, BME >5mm and erosion were highly specific for axSpA.

Data-driven definitions for active and structural MRI lesions in the sacroiliac joint in spondyloarthritis and their predictive utility

Objectives

To determine quantitative SI joint MRI lesion cut-offs that optimally define a positive MRI for inflammatory and structural lesions typical of axial SpA (axSpA) and that predict clinical diagnosis.

Methods

The Assessment of SpondyloArthritis international Society (ASAS) MRI group assessed MRIs from the ASAS Classification Cohort in two reading exercises where (A) 169 cases and 7 central readers; (B) 107 cases and 8 central readers. We calculated sensitivity/specificity for the number of SI joint quadrants or slices with bone marrow oedema (BME), erosion, fat lesion, where a majority of central readers had high confidence there was a definite active or structural lesion. Cut-offs with ≥95% specificity were analysed for their predictive utility for follow-up rheumatologist diagnosis of axSpA by calculating positive/negative predictive values (PPVs/NPVs) and selecting cut-offs with PPV ≥ 95%.

Results

Active or structural lesions typical of axSpA on MRI had PPVs ≥ 95% for clinical diagnosis of axSpA. Cut-offs that best reflected a definite active lesion typical of axSpA were either ≥4 SI joint quadrants with BME at any location or at the same location in ≥3 consecutive slices. For definite structural lesion, the optimal cut-offs were any one of ≥3 SI joint quadrants with erosion or ≥5 with fat lesions, erosion at the same location for ≥2 consecutive slices, fat lesions at the same location for ≥3 consecutive slices, or presence of a deep (i.e. &gt;1 cm depth) fat lesion.

Conclusion

We propose cut-offs for definite active and structural lesions typical of axSpA that have high PPVs for a long-term clinical diagnosis of axSpA for application in disease classification and clinical research.

Influence of pregnancy/childbirth on long-term bone marrow edema and subchondral sclerosis of sacroiliac joints

OBJECTIVE

To investigate long-term effects of pregnancy/childbirth on bone marrow edema (BME) and subchondral sclerosis of sacroiliac joints (SIJ) in comparison to MRI changes caused by spondyloarthritis (SpA) and assess the influence of birth method and number of children on SIJ-MRI changes.

MATERIALS AND METHODS

This is a retrospective cohort study with 349 women (mean age 47 ± 14 years) suffering low back pain. Four subgroups were formed based on SpA diagnosis and childbirth (CB) history. Two musculoskeletal radiologists scored the presence of BME and sclerosis on SIJ-MRI using the Berlin method. Further, an 11-point "global assessment score" representing the overall confidence of SpA diagnosis based on MRI was evaluated in addition to the ASAS (Assessment of Spondyloarthritis International Society) criterion of "positive MRI" for sacroiliitis.

RESULTS

CB did not correlate with BME score (p = 0.38), whereas SpA diagnosis was associated with a higher BME score (r = 0.31, p < 0.001). Both CB (r = 0.21, p < 0.001) and SpA diagnosis (r = 0.33, p < 0.001) were correlated with a higher sclerosis score. CB was not associated with a higher confidence level in diagnosing SpA based on MRI (p = 0.07), whereas SpA diagnosis was associated with a higher score (r = 0.61, p < 0.001). Both CB (phi = 0.13, p = 0.02) and SpA diagnosis (phi = 0.23, p < 0.001) were significantly associated with a positive ASAS criterion for sacroiliitis. In non-SpA patients with CB, number of children (p = 0.001) was an independent predictor of sclerosis score, while birth method yielded no significant effect (p = 0.75).

CONCLUSION

Pregnancy/CB has no impact on long-term BME on SIJ, however, may cause long-term subchondral sclerosis-similar to SpA-associated sclerosis. Number of children is positively correlated with SIJ sclerosis. Birth method yields no effect on SIJ sclerosis.