Prevalence of Inflammatory Back Pain in a Low-Income Population

Background Inflammatory back pain (IBP) is a major criterion in identifying axial spondyloarthritis. Whether socioeconomic issues impact prevalence of IBP assessed using standardized questionnaires has not been assessed. We determined IBP prevalence and performance of IBP questionnaires in a low-income, low-literacy population. Methods Individuals were interviewed in Fortaleza, Brazil, for the prevalence of IBP using Calin's, Berlin, and ASAS IBP questionnaires; monthly family income (US dollars), literacy (>/<= 8 school years [SYs]), and smoking habit (present/absent) were registered. Results Two hundred nineteen individuals were included (mean age, 38.2 +/- 12.9 years), 110 (50.2%) men, 58 (26.4%) White, and 38 (17.3%) smokers. Overall, 152 (69.4%) declared <US $720 (mean local income) earnings, and 64 (29.2%) had <= 8 SYs. Chronic back pain was declared by 134 (61%) with 32 (14.6%), 25 (11.9%), and 63 (28.3%) fulfilling ASAS, Berlin, and Calin's IBP criteria, respectively. Chronic back pain or IBP prevalence was similar regardless of ethnicity, smoking habit, income, or literacy with IBP prevalence higher among women (p = 0.006). Conclusions This is the first report on IBP prevalence in a low-income, low-literacy population. Chronic back pain was highly prevalent with almost 15% having IBP using ASAS criteria. Inflammatory back pain prevalence looked similar using ASAS and Berlin criteria; values were higher using Calin's criteria. Literacy or income did not influence IBP prevalence in this population, which was higher among women. The higher prevalence of IBP using Calin's criteria in this population should be taken into account as it might impact studies aiming to determine prevalence of axial spondyloarthritis in clinical studies in this scenario.