Plain radiographs as an outcome measure in ankylosing spondylitis.

Radiographic evidence of sacroiliitis is a prerequisite for classification according to the (modified) New York criteria. Structural damage is also an important endpoint in the assessment of ankylosing spondylitis (AS). However, little research has been done on the development, validation, and application of scoring methods for radiographic changes in AS. Methodological issues that can be addressed concerning radiographic scoring methods are discussed in detail. A short introduction to the available scoring methods is presented.