Four patterns of SpA progression identified

Trajectory modelling of radiographic spinal disease in ankylosing spondylitis has identified four patterns of disease which will provide more clarity to researchers and clinicians.

A 15-year follow-up of the Prospective Study of Outcomes in Ankylosing Spondylitis (PSOAS) observational cohort, analysed 1,618 radiographs from 561 patients between 2002 and 2017.

The study, published in Rheumatology, identified patients as either non-progressors, late progressors, early progressor or rapid progressors.

“We found that clinical factors that were more associated with greater mSASSS [modified Stoke Ankylosing Spondylitis Spinal Score] disease/trajectory group included male gender, white race, elevated CRP, and smoking history.”

“The non-progressor group was younger and has less disease duration compared to other groups.”

There was no significant difference in HLA-B27 positivity between the four groups.

The investigators said current studies of disease-modifying agents on spinal structural disease have been mixed. Being able to divide patients into more homogenous subgroups, may help in both mechanistic studies on the underlying pathophysiology of the disease and in clinical trials.

The study also found TNFi utilisation was associated with decreased progression as measured by mSASSS in the rapid progressor group.

“Moreover, the benefit of TNFi treatment in our rapid-progressor group was time-dependent as earlier intervention would lead to greater decreases in mSASSS given the curvilinear trajectory.”

“This has important clinical implications as this suggests that while all patients may not benefit from pharmacotherapy, our rapid-progressor patient subgroup, which has the highest disease burden of spinal disease, is a group that benefits from use of TNFi medication potentially independent of CRP elevation.”

They said the finding, if confirmed in subsequent clinical trials, could be paradigm-shifting given current treatment recommendations were based on disease activity.

Co-investigator Professor Matt Brown, now director of the Guy’s and St Thomas’ NHS Foundation Trust and King’s College London NIHR Biomedical Research Centre, told the limbic there was a clear need to identify patients particularly with early axSpA, even nr-axSpA, who have poor prognosis, particularly functionally.

“Radiographic measures correlate well with functional outcomes measured objectively (such as metrology), so the paper’s finding confirming that males, with an elevated baseline CRP, who smoke, are likely to do worse, helps emphasise that that group are most likely to benefit from interventions.”

“Conversely, women who do not smoke and do not have elevated CRPs can be reassured that functionally and radiographically they should do well.”

He said the study’s findings required validation in an independent group while assessment in non-radiographic axSpA was another line of enquiry.

As well, investigations were needed to identify other biomarkers that may be helpful in predicting trajectory, or which improve understanding of why the disease follows these different patterns.

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