The US national prevalence of spondylarthritis (SpA) was estimated for 2 published sets of classification criteria: the Amor criteria and the European Spondylarthropathy Study Group (ESSG) criteria. These 2 SpA criteria sets have been the most widely utilized in previous population-based studies of SpA.
The US SpA prevalence estimates were based on a representative sample of 5,013 US adults ages 20-69 years who were examined in the US National Health and Nutrition Examination Survey (NHANES) 2009-2010.
The overall age-adjusted prevalence of definite and probable SpA by the Amor criteria was 0.9% (95% confidence interval [95% CI] 0.7-1.1%), corresponding to an estimated 1.7 million persons (95% CI 1.4-2.1 million persons). The age-adjusted prevalence of SpA by the ESSG criteria was 1.4% (95% CI 1.0-1.9%), corresponding to an estimated 2.7 million persons (95% CI 1.9-3.7 million persons). There were no statistically significant sex differences in SpA prevalence. The SpA prevalence among non-Hispanic white persons was 1.0% (95% CI 0.7-1.5%) by the Amor criteria and 1.5% (95% CI 1.0-2.3%) by the ESSG criteria. SpA prevalence could not be reliably estimated in other race/ethnicity subgroups due to sample size imitations.
The SpA prevalence estimates are in the range of SpA prevalence estimates reported elsewhere in population-based surveys and it is likely that SpA may affect up to 1% of US adults, a prevalence similar to that reported for rheumatoid arthritis. The current US SpA prevalence estimates may be lower than the true value because the NHANES 2009-2010 data collection did not capture a complete set of the elements specified in the 2 SpA criteria sets.