Background The symptom of inflammatory back pain (IBP) is regarded as an important clinical parameter for axial spondyloarthritis (axSpA) and is often used in a diagnostic approach.

Objectives To compare IBP criteria as a diagnostic tool for the rheumatologist. Furthermore, to assess the performance of the IBP criteria when assessed by a blinded rheumatologist, the diagnosing rheumatologist and self-assessed by the patient.

Methods Patients with chronic back pain starting at an age <45 years who were referred to a rheumatologist because of unclear diagnosis were consecutively included in this study. A questionnaire containing all relevant IBP parameters were first answered by the patient (pat), followed by a rheumatologist blinded (rh-blind) for presence or absence of other SpA-features and blinded for the diagnosis, and finally by the rheumatologist responsible for the diagnosis (rh-diag). Previously published Calin- (1), Berlin- (2) and ASAS criteria (3) as well as single items of IBP were compared regarding sensitivity, specificity and agreement between the two investigators and patient.

Results Six rheumatology practices or outpatient clinics in Germany participated in this study, investigating altogether 405 patients referred to them. A diagnosis of axial SpA was made in 180 (44.4%), AS in 88 and nr-axSpA in 92 patients. There was no clear superiority of any oft he 3 criteria regarding sensitivity for AS or nr-axSpA with an overall sensitivity of about 80% for all 3 groups (Table). The specificity was expectedly low (Table) because patients from the control group (diagnosis of non-SpA) were also partly referred because of unclear back pain including IBP. No single IBP parameter showed superiority regarding sensitivity or specificity in comparison to the criteria sets. Interestingly, agreement between the 2 rheumatologists was relatively good with 83.9% regarding the Berlin-, 77.2% regarding the ASAS- and 81.1% regarding the Calin-criteria for all axial SPA patients. There was about 10% less agreement in axial SPA patients with 74.0%, 68.4% and 71.2%, respectively, between all 3 ratings (pat, rh-blind, rh-diag).

Conclusions All 3 sets of IBP criteria performed similarly well with a good accordance between rheumatologists but also an acceptable accordance between rheumatologists and patients.

1. Calin et al, JAMA 1977; 237:261

2. Rudwaleit et al, Arthritis Rheum 2006; 54: 569-78

3. Sieper et al, Ann Rheum Dis 2009; 68: 784-788

Disclosure of Interest M. Rudwaleit Speakers Bureau: Pfizer/Wyeth Pharmaceuticals, Merck Sharp Dohme/Schering Plough, Abbott Immunology Pharmaceuticals, UCB: consulting fees or other remuneration, I. Spiller: None Declared, J. Callhoff: None Declared, J. Wendler: None Declared, J. Brandt: None Declared, J. Listing Grant/Research support from: Abbott, Merck, Pfizer, UCB, Roche, BMS, J. Sieper Grant/Research support from: Abbott, Merck, Pfizer, Consultant for: Abbott, Merck, Pfizer, Speakers Bureau: Abbott, Merck, Pfizer