The NIH (National Institutes of Health) is seeking individuals with ankylosing spondylitis to participate in research seeking to identify the genes that may affect the severity of this disease. For more info. visit www.clinicaltrials.gov or call the NIH Patient Recruitment Office at 866-411-1010.

Here is the link to the study
http://clinicalstudies.info.nih.gov/detail/A_2003-AR-0131.html

Unfortunately, it does not appear to have multiple study sites, only in Maryland.

On a related note, two new genes have been discovered that account for 70% of the susceptibility to AS
http://www.spondylitis.org/spondyplus.aspx?YYZ=004CA

Jan