To evaluate similarities and differences between non-radiographic axial spondyloarthritis (nr-axSpA) and ankylosing spondylitis (AS) with regard to treatment effects and clinical, humanistic, and economic burdens.
In this systematic literature review, ACR 2015, EULAR 2015, EMBASE, and PubMed were searched for studies published between January 2010 and September 2015 that compared predefined clinical, humanistic, and economic aspects in nr-axSpA and AS. Publications were processed according to PRISMA guidelines, analyzed according to four research questions, and assessed for the GRADE level of evidence.
Of 220 titles screened, 50 studies were evaluable. Treatment effects were reported by 22; clinical, humanistic, and economic burdens were specified by 38, 4, and 0, respectively. Fewer patients with increased C-reactive protein levels, less extensive structural damage, slower radiographic progression, and significantly lower Bath AS Metrology and Bath AS Functional Indices were reported for nr-axSpA than for AS. In contrast, the Bath AS Disease Activity Index, AS Disease Activity Score, and health-related quality of life were similar, indicating comparable clinical and humanistic burdens. Response to conventional therapies and TNFα inhibitors was similar between nr-axSpA and AS patients, although TNFα inhibitors were prescribed less frequently to nr-axSpA patients.
Whether nr-axSpA is regarded as an early form of AS or as a distinct disease entity, it represents an important subgroup of axSpA. Ongoing clinical trials may provide the required evidence for a specified indication for TNFα inhibitors, important to prevent off-label use. Further research is crucial to better understand the disease spectrum and predictors of progression.