Background: Undiagnosed cases of seronegative spondyloarthropathy (Spa) are often observed during epidemiologic studies.
Objective: To determine the extent of and the reasons for the underdiagnosis of Spa.
Methods: We studied 2 groups of Alaskan native patients with Spa using a standardized protocol that included an interview, physical examination, medical record review, and radiographic and laboratory examinations. One group consisted of patients identified in a communitywide epidemiologic study; the other group consisted of patients from related but geographically separate populations who had been diagnosed by a specialist in the hospital or a specialty clinic. All cases met the current classification criteria for Spa. The clinical and demographic features of the cases in the 2 groups were compared.
Results: Fifty-five (72%) of the 76 community cases that we identified in the epidemiologic study had not been diagnosed previously as Spa. Among the undiagnosed patients were 34 (94%) of the 36 women, 11 (65%) of the 17 patients with ankylosing spondylitis, 12 (36%) of the 33 patients with reactive arthritis, and 24 (100%) of those with undifferentiated Spa. The community and specialty clinic patient groups were similar in age of onset of joint and back pain and in overall symptoms. The specialty clinic group had a higher proportion of men, more severe disease, and a higher frequency of iritis.
Conclusions: The diagnosis of Spa was missed more often than not in the primary care setting, probably because most of the cases were of mild or moderate severity and did not fit the classic descriptions of spondyloarthropathic disorders. The higher proportion of men among the specialty clinic cases probably reflects provider expectation as well as a slightly milder disease course in women.