<qa>  What is the BASFI validated in?Study of patients with AS for 20 years or more will provide a sample with a greater proportion of patients who will have developed the outcomes of interest. All participants will necessarily be age 37 or older. Study entry is not limited by sex or ethnic origin. English literacy is required because the functional status questionnaires used in the study have not been developed and validated in many languages other than English. In particular, the HAQ-S has been validated in only English, Dutch, and Finnish. The BASFI has been validated in English, Dutch, Finnish, Swedish, German, and French. Each of these validation studies consists of a single report. Monolingual speakers of these languages are likely to be rare in our area. 