HealthDay News – For patients with chronic back pain, the presence of at least one of three spondyloarthritis (SpA) features can identify possible axial spondyloarthritis (axSpA), according to a study published online Jan. 27 in Arthritis & Rheumatology.

Atul Deodhar, M.D., from the Oregon Health & Science University in Portland, and colleagues enrolled 751 U.S. patients in a study to identify the proportion with axSpA among those with chronic back pain and one or more of three SpA features. Participants had to have chronic back pain for three months or longer, starting before age 45 years, and have one or more of the following: positive human leukocyte antigen B27, current inflammatory back pain, and magnetic resonance imaging/X-ray evidence of sacroiliitis. None of the patients had a prior SpA diagnosis.

The researchers found that 46% of the 697 patients with available data were given a clinical diagnosis of axSpA by the investigator. Overall, 47% of 744 participants met the Assessment of SpondyloArthritis international Society (ASAS) criteria for axSpA. Of these, 238 were classified as non-radiographic axSpA, and 108 had ankylosing spondylitis; two of the patients had missing data. Specificity and sensitivity of the ASAS criteria were 79 and 81 percent, respectively, using the investigator’s clinical diagnosis as gold standard.

“Among patients with chronic back pain for ≥3 months beginning at age <45 years, the presence of ≥1 of 3 SpA features is an effective way to identify patients with possible axSpA,” the authors write.

Several authors disclosed financial ties to pharmaceutical companies, including AbbVie, which funded the study.


Summary and Clinical Applicability

AxSpA, including both AS and nr-axSpA, can generally be diagnosed based on a pattern of clinical, laboratory, and imaging findings that include chronic back pain, sacroiliitis on imaging, and the presence of human leukocyte antigen (HLA) B27. AS, however, is more easily identified by the presence of sacroiliitis on radiographs.  This study determined that a patient with chronic back pain lasting longer than 3 months, with onset before age 45, should have an anterior-posterior (AP) plain radiograph of the pelvis to examine the sacroiliac (SI) joints. For patients who are not positive for sacroiliitis by plain radiography, the presence of specific features of SpA makes the diagnosis of nr-axSpA likely. The findings of this study are significant because the likelihood of early diagnosis and intervention depends on the specific findings associated with a particular disease.

Reference

Deodhar A, Mease PJ, Reveille JD, et al. Frequency of axial spondyloarthritis diagnosis among patients seen by United States rheumatologists for evaluation of chronic back pain. Arthritis Rheum. 2016; doi: 10.1002/art.39612.