Most specific for diagnosing Ankylosing spondyliti?
High-Yield Explanation
According to Modified New York criteria, the diagnosis of definite AS requires the following: established sacroiliitis on radiographs (unilateral or bilateral) and at least one of the following clinical criteria: (1) low back pain and stiffness for more than 3 months improving with activity, (2) reduced chest expansion (3) limited lumbar movements. HLA B27 is present in > 90% cases of ankylosing spondylitis but it is not specific for AS.