Easy probability estimation of the diagnosis of early axial spondyloarthritis by summing up scores

Performance of clinical, laboratory and imaging features for diagnosing spondyloarthritis-a systematic literature review and meta-analysis

OBJECTIVE

The Berlin algorithm was developed to help diagnose axial SpA (axSpA), but new studies suggest some features typical of SpA are less specific than previously assumed. Furthermore, evidence is lacking for other SpA subtypes (e.g. peripheral SpA). We aimed to review the evidence on the performance of SpA features for diagnosing each SpA subtype.

METHODS

We conducted a systematic literature review of studies reporting the diagnostic performance of one or more SpA features in patients with suspected SpA. The external reference was the rheumatologist's diagnosis of SpA. Meta-analysis was performed, separately for each SpA subtype, to estimate pooled sensitivity, specificity and positive and negative likelihood ratios (LR+ and LR-, respectively). Meta-regression assessed the effect of covariates (e.g. feature's prevalence) on each feature's performance.

RESULTS

Of 13 844 articles screened, 46 were included. Sacroiliitis on MRI, damage on pelvic radiographs and elevated CRP had the best balance between LR+ and LR- (LR+ 3.9-17.0, LR- 0.5-0.7) for diagnosing axSpA. HLA-B27 had an LR+ lower than anticipated (LR+ 3.1). Inflammatory back pain (IBP) had a low LR+ (LR+ ≈1), but substantially decreased the likelihood of axSpA when absent (LR- 0.3). Conversely, peripheral features and extramusculoskeletal manifestations showed a high LR+ (LR+ 1.6-5.0), but were as common in axSpA as non-axSpA (LR- ≈1). The specificity of most features was reduced in settings when these were highly prevalent. Limited data precluded a detailed analysis on diagnosing other SpA subtypes.

CONCLUSION

Imaging features and CRP have good diagnostic value for axSpA. However, the specificity of other features, especially HLA-B27 and IBP, is lower than previously known.

Can rheumatologists unequivocally diagnose axial spondyloarthritis in patients with chronic back pain of less than 2 years duration? Primary outcome of the 2-year SPondyloArthritis Caught Early (SPACE) cohort

OBJECTIVES

To investigate the prevalence of axial spondyloarthritis (axSpA) in patients with chronic back pain (CBP) of less than 2 years (2y) duration referred to the rheumatologist, the development of diagnosis over time, and patient characteristics of those developing definite (d-)axSpA over 2y.

METHODS

We analysed the 2y data from SPondyloArthritis Caught Early, a European cohort of patients (<45 years) with CBP (≥3 months, ≤2y) of unknown origin. The diagnostic workup comprised evaluation of clinical SpA features, acute phase reactants, HLA-B27, radiographs and MRI (sacroiliac joints and spine), with repeated assessments. At each visit (baseline, 3 months, 1y and 2y), rheumatologists reported a diagnosis of axSpA or non-axSpA with level of confidence (LoC; 0-not confident at all to 10-very confident).

MAIN OUTCOME

axSpA diagnosis with LoC≥7 (d-axSpA) at 2y.

RESULTS

In 552 patients with CBP, d-axSpA was diagnosed in 175 (32%) at baseline and 165 (30%) at 2y. Baseline diagnosis remained rather stable: at 2y, baseline d-axSpA was revised in 5% of patients, while 8% 'gained' d-axSpA. Diagnostic uncertainty persisted in 30%. HLA-B27+ and baseline sacroiliitis imaging discriminated best 2y-d-axSpA versus 2y-d-non-axSpA patients. Good response to non-steroidal anti-inflammatory drugs and MRI-sacroiliitis most frequently developed over follow-up in patients with a new d-axSpA diagnosis. Of the patients who developed MRI-sacroiliitis, 7/8 were HLA-B27+ and 5/8 male.

CONCLUSION

A diagnosis of d-axSpA can be reliably made in nearly one-third of patients with CBP referred to the rheumatologist, but diagnostic uncertainty may persist in 5%-30% after 2y. Repeated assessments yield is modest, but repeating MRI may be worthwhile in male HLA-B27+ patients.

Classification vs diagnostic criteria: the challenge of diagnosing axial spondyloarthritis

In recent years, significant progress has been made in improving the early diagnosis of spondyloarthritides (SpA), including axial SpA. Nonetheless, there are still issues related to the application of classification criteria for making the primary diagnosis of SpA in the daily practice. There are substantial conceptional and operational differences between the diagnostic vs classification approach. Although it is not possible to develop true diagnostic criteria for natural reasons as discussed in this review, the main principles of the diagnostic approach can be clearly defined: consider the pre-test probability of the disease, evaluate positive and negative results of the diagnostic test, exclude other entities, and estimate the probability of the disease at the end. Classification criteria should only be applied to patients with an established diagnosis and aimed at the identification of a rather homogeneous group of patients for the conduction of clinical research.

Nonradiographic axial spondyloarthritis

Non-radiographic axial spondyloarthritis (nr-axSpA) is a complex disease process that is part of the spectrum of axial spondyloarthritis (axSpA). This article reviews the current state of the literature as the understanding of this disease spectrum expands. The conceptual history and terminology, genetics, and epidemiology are reviewed. The clinical manifestations, diagnostic approach, and measures of disease activity are examined. Finally the current treatment modalities and recommendations and the research agenda for nr-axSpA are reviewed. With the advent of new criteria, the disease spectrum can be studied in a systematic manner. These data have enriched our knowledge that reflects an earlier or milder form of disease on a spectrum same as that of ankylosing spondylitis (or radiographic axSpA). We learned how patients present in this stage and that despite an unacceptable delay in diagnosis (regardless of the stage), the burden of disease is high and unremitting. nr-axSpA clinical trials have been somewhat heterogeneous (with variable inclusion criteria) but have nevertheless shown considerable efficacy with tumor necrosis factor inhibitors and flare on withdrawal of therapy.

Anti-CD74 antibodies have no diagnostic value in early axial spondyloarthritis: data from the spondyloarthritis caught early (SPACE) cohort

BACKGROUND

Anti-CD74 IgG antibodies are reported to be elevated in patients with axial spondyloarthritis (axSpA). This study assessed the diagnostic value of anti-CD74 antibodies in patients with early axSpA.

METHODS

Anti-CD74 IgG and IgA antibodies were first measured in an exploratory cohort of patients with radiographic axSpA (138 patients with ankylosing spondyloarthritis (AS)) and 57 healthy controls and then were measured in patients with early axSpA (n = 274) and with non-SpA chronic back pain (CBP) (n = 319), participating in the spondyloarthritis caught early (SPACE) prospective cohort study of patients under 45 years old with early back pain (for ≥ 3 months, but ≤ 2 years).

RESULTS

In the exploratory cohort, anti-CD74 IgG antibodies were present in 79.7% of patients with AS vs. 43.9% of healthy controls (p < 0.001). Anti-CD74 IgA antibodies were present in 28.5% of patients with AS vs. 5.3% of healthy controls (p < 0.001). In the SPACE cohort, anti-CD74 IgG antibody levels were present in 46.4% of the patients with axSpA vs. 47.9% of the patients with CBP (p = 0.71). Anti-CD74 IgA antibodies were present in 54.7% of the patients with axSpA and 37.0% of the patients with CBP (p < 0.001). This resulted in a positive predictive value of 58.8% (compared to a prior probability of 46.2%) and a negative predictive value of 59.1% (compared to a prior probability of 53.8%). In a regression model, total serum IgA was associated with axSpA odds ratio (OR) 1.19, p < 0.001) whereas anti-CD74 IgA was not (OR) 1.01, p = 0.33). Furthermore, anti-CD74 IgA was associated with sacroiliitis on magnetic resonance imaging (MRI) (OR) = 2.50, p = 0.005) and heel enthesitis (OR) = 2.56, p = 0.002).

CONCLUSIONS

Albeit anti-CD74 IgA is elevated in patients with early axSpA, this elevation is not sufficiently specific to yield significant diagnostic value in patients under 45 years old presenting with early back pain.

Developing a Risk-scoring Model for Ankylosing Spondylitis Based on a Combination of HLA-B27, Single-nucleotide Polymorphism, and Copy Number Variant Markers

OBJECTIVE

To develop a genotype-based ankylosing spondylitis (AS) risk prediction model that is more sensitive and specific than HLA-B27 typing.

METHODS

To develop the AS genetic risk scoring (AS-GRS) model, 648 individuals (285 cases and 363 controls) were examined for 5 copy number variants (CNV), 7 single-nucleotide polymorphisms (SNP), and an HLA-B27 marker by TaqMan assays. The AS-GRS model was developed using logistic regression and validated with a larger independent set (576 cases and 680 controls).

RESULTS

Through logistic regression, we built the AS-GRS model consisting of 5 genetic components: HLA-B27, 3 CNV (1q32.2, 13q13.1, and 16p13.3), and 1 SNP (rs10865331). All significant associations of genetic factors in the model were replicated in the independent validation set. The discriminative ability of the AS-GRS model measured by the area under the curve was excellent: 0.976 (95% CI 0.96-0.99) in the model construction set and 0.951 (95% CI 0.94-0.96) in the validation set. The AS-GRS model showed higher specificity and accuracy than the HLA-B27-only model when the sensitivity was set to over 94%. When we categorized the individuals into quartiles based on the AS-GRS scores, OR of the 4 groups (low, intermediate-1, intermediate-2, and high risk) showed an increasing trend with the AS-GRS scores (r² = 0.950) and the highest risk group showed a 494× higher risk of AS than the lowest risk group (95% CI 237.3-1029.1).

CONCLUSION

Our AS-GRS could be used to identify individuals at high risk for AS before major symptoms appear, which may improve the prognosis for them through early treatment.