The rheumatologist-judged Inflammatory Back Pain (IBP) or criteria for IBP established for ankylosing spondylitis may not perform well when determining axial involvement in Psoriatic Arthritis (PsA), says the study results published in 'Annals of the Rheumatic Diseases'.

The investigators focused on ascertaining the agreement between rheumatologist-judged IBP and criteria defining IBP in patients with PsA and predictive value of IBP in recognising the axial involvement in PsA.To justify the basis of this study, Kristy S Yap et al. used the prospectively collected data and analysed the agreement between rheumatologist judgement of IBP and IBP criteria (Calin, Rudwaleit and Assessment of Spondyloarthritis International Society) via the kappa coefficient. The sensitivity, specificity and likelihood ratios of the presence of back pain, rheumatologist-judged IBP and the three IBP criteria for identifying axial PsA (AxPsA) were also deduced. Lastly, the clinical and genetic markers in PsA patients with axial radiological changes with and without back pain were compared.A total of 171 patients (52% male, mean age 46.6 years) were recognised. Ninety-six (56.13%) patients described chronic back pain. Sixty-five (38.01%) had IBP, and fifty-four (32%) patients had evidence of radiological change in the spine. The highest value for the Calin criteria (0.70) supported the agreement between rheumatologist judgement of IBP and IBP criteria. There was a favourable likelihood ratio for the presence of radiological axial involvement, which was highest for the Rudwaleit criteria (2.17). There were no dissimilarities between patients with AxPsA having back pain or no back pain. Although, higher Bath Ankylosing Spondylitis Disease Activity Index and lower incidence of human leucocyte antigen-B*38 were observed in patients with back pain

."The rheumatologists should consider conducting axial imaging in all the patients with PsA despite the presence or the nature of back pain to distinguish the patients with poorer prognosis", the investigators concluded.