Age at onset in axial spondyloarthritis around the world: data from the Assessment in SpondyloArthritis international Society Peripheral Involvement in Spondyloarthritis study.

OBJECTIVE: Age at onset is useful in identifying chronic back patients at an increased risk of axial SpA (axSpA). However, the majority of data on which the criterion of age at onset <45 years is based originates from Europe. Therefore it is unknown if this criterion applies in other parts of the world. We aimed to assess the age at onset of axSpA and its relationship with HLA-B27 and gender across the world. METHODS: Analyses were applied to patients from 24 countries across the world with an axSpA diagnosis and known age at onset of axial complaints. Cumulative probability plots were used to display the cumulative distribution of age at onset of axial symptoms. Linear regression models were built to assess the effect of HLA-B27 and gender on age at onset of axial symptoms. RESULTS: Of 2579 axSpA patients, 92% had an age at onset of axial symptoms <45 years, with only small variations across the geographical regions [Asia, n = 574 (94%); Europe and North America, n = 988 (92%); Latin America, n = 246 (89%); Middle East and North Africa, n = 771 (91%)]. Age at onset of axial symptoms was consistently lower in HLA-B27-positive patients {median 25 years [interquartile range (IQR) 19-32] vs 31 [IQR 22-39]} and male patients [median 25 years (IQR 19-33) vs 28 (IQR 21-37)], but in multivariable models an additional statistically significant effect of male gender independent of HLA-B27 was only found in Asia. CONCLUSION: Around the world, the great majority of axSpA patients had an age at onset of axial disease of <45 years, with HLA-B27 and male gender associated with earlier disease onset.

Baseline factors that influence ASAS 20 response in patients with ankylosing spondylitis treated with etanercept.

OBJECTIVE: To examine the baseline demographic and disease characteristics that might influence improvement as measured by the Assessment in Ankylosing Spondylitis Response Criteria (ASAS 20) in patients with ankylosing spondylitis (AS). METHODS: A multicenter Phase 3 study was performed to compare the safety and efficacy of 24 weeks of etanercept 25 mg subcutaneous injection twice weekly (n = 138) and placebo (n = 139) in patients with AS. The ASAS 20 was measured at multiple time points. Using a significance level of 0.05, a repeated measures logistic regression model was used to determine which baseline factors influenced response in the etanercept-treated patients during the 24-week double blind portion of the trial. The following baseline factors were used in the model: demographic and disease severity variables, concomitant medications, extra-articular manifestations, and HLA-B27 status. The predictive capability of the model was then tested on the patients receiving placebo after they had received open-label etanercept treatment. RESULTS: Baseline factors that were significant predictors of an ASAS 20 response in etanercept-treated patients were C-reactive protein (CRP), back pain score, and Bath Ankylosing Spondylitis Functional Index (BASFI) score. Although clinical response to etanercept was seen at all levels of baseline disease activity, responses were consistently more likely with higher CRP levels or back pain scores and less likely with increased BASFI scores at baseline. CONCLUSIONS: Higher CRP values and back pain scores and lower BASFI scores at baseline were significant predictors of a higher ASAS 20 response in patients with AS receiving etanercept but predictive value was of insufficient magnitude to determine treatment in individual patients.

Assessment of radiographs in longitudinal observational studies.

Radiographs are important to assess structural damage in longitudinal studies. This article describes several issues on the selection of films, frequency of followup, scoring of radiographs, and presentation of results, especially in the context of longitudinal studies.

Principles of assessment from a clinical perspective.

Physicians apply assessments every day in clinical practice. Common clinical practice is impossible without measurements and tests. Testing looks rather straightforward: a test result is either positive or negative. Unfortunately, this simplicity is not in keeping with truth. At the base of measuring and testing in clinical practice lies the assumption of uncertainty: we do not know whether a patient has a disease, we can only estimate the probability that he has a disease by performing a (chain of) test(s). Every test result leaves open the chance that a wrong decision is taken on the basis of the test result. It is a challenge for the clinician to get a better insight into this process, as well as to minimize the chance of wrong decisions. By using a number of clinical examples, we describe here the principles of assessment from two different perspectives: the perspective of the test, and the perspective of the individual patient. The former perspective incorporates test-specific characteristics, such as sensitivity, specificity, accuracy and cut-off levels, and the latter deals with individual probabilities from a 'Bayesian' concept.