The 10-item SIMPLE screening questionnaire for axSpA is a patient self-report standardized questionnaire developed by rheumatologists from the Spondyloarthritis Research Consortium of Canada and patient consumers. It elicits responses to domains comprising inflammatory back pain (IBP). We aimed to test the construct validity of the items comprising this questionnaire by comparing responses with those elicited independently by rheumatologists and by evaluating their association with severity of back pain and diagnosis of axSpA.

The multicenter Screening for Axial Spondyloarthritis in Psoriasis, Iritis, and Colitis (SASPIC) Study is aimed at early detection of axial SpA in consecutive patients presenting with undiagnosed back pain to the rheumatologist. Consecutive patients ≤45 years of age with ≥3 months undiagnosed back pain with any one of psoriasis, acute anterior uveitis (AAU), or colitis undergo routine clinical evaluation by a rheumatologist for axSpA. Patients first complete the SIMPLE questionnaire and then the rheumatologist independently of any patient data determines the presence or absence of a diagnosis of axial SpA. Agreement between patient and physician reporting of questions reflecting IBP domains was analyzed using the kappa statistic. Proportions of patients reporting to the various IBP domain questions were compared according to back pain score ≥5 or <5 (0-10NRS) using the chi-square. Associations between patient responses for different IBP domain items and a diagnosis of axSpA were analyzed by regression.

234 patients (51.3% male, mean age 34.6 years, mean symptom duration 7.0 years, mean back pain duration 7.1 years, B27+ 36.3%) were referred with AAU (29.9%), psoriasis (18.8%), Crohn’s colitis (32.1%), ulcerative colitis (19.2%). Patients responded to SIMPLE items reflecting stiffness, nocturnal awakening, improvement with exercise, and response to NSAID significantly more frequently when back pain score was ≥5. Agreement between patient and physician reporting for IBP domains was substantial for duration of stiffness (κ=0.57) and nocturnal awakening (κ=0.63), but less for effect of exercise (κ=0.30), effect of rest (κ=0.44), and response to NSAID (κ=0.31). Most of the SIMPLE items were significantly associated with diagnosis of axSpA with the exception of items describing alleviation of symptoms by exercise and NSAID therapy (Table).

Patient reporting to IBP domains of stiffness and nocturnal pain are congruent with physician reporting and associate strongly with final diagnosis of axSpA. Reporting of impact of exercise and NSAID is variable and dependent on level of back pain.

Table.