HLA-B27 Positive and HLA-B27 Negative Ankylosing Spondylitis: A Comparative Study in Diagnostic Process and Clinical Features

ABSTRACT

OBJECTIVE: To investigate the differences in clinical and radiologic features between HLA-B27 positive ankylosing spondylitis (AS) and HLA B27 negative AS METHOD: Ninety-nine consecutive patients who were suspected as AS in initial diagnostic process were studied. HLA-B27 was examined with microlymphocytotoxicity method in all patients. A radiologist and a physiatrist re- read plain pelvis radiographies of all patients. Difference in onset age and C-reactive protein (CRP) depending on HLA B27 status and an association between HLA B27 status and clinical and radiologic features were tested. RESULTS: Sacroiliitis (> or =bilateral grade 2) was identified in 63 of 77 patients with HLA B27 and 7 of 22 patients without HLA B27 through the re-reading process. Ten percent of definite AS was HLA B27 negative AS. Five of 22 patientswithout HLA B27 were diagnosed as diffuse idiopathic skeletal hyperostosis. There was a significant association between sacroiliitis (> or =bilateral grade 2) and HLA B27 (p or =unilateral grade 1). None of clinical and radiologic parameters are associated with HLA B27 status. It does not make difference in onset age of AS. To make a more concrete conclusion, a study of a much larger number of HLA B27 negative AS patients will be necessary.