Assessment of disease severity (in terms of function) using the internet.

Objective: To determine whether visual analog scales (VAS) can be used over the Internet to assess the patient with ankylosing spondylitis (AS) accurately or if the use of this different medium will affect the results.

Methods: Patients with AS (n = 50) attending a physiotherapy/educational course completed both an Internet based and a paper based version of the Bath Ankylosing Spondylitis Functional Index (BASFI) that uses VAS. The Internet version was completed twice to assess intrarespondent variation reliability and compared with the paper version to assess interrespondent variation reliability. Patients were also asked to assess ease of use and to suggest changes to the Internet version.

Results: The interclass coefficient of intra- and interrespondent reliability were 0.989 (p < 0.001) and 0.976 (p < 0.001), respectively. There was a 3% difference in assessments carried out over the Internet compared to those on paper and a 2% difference in repeatability of Internet assessed questionnaires. Bland and Altman plots showed a mean difference between paper compared to the Internet version was 0.0156 with 95% limits of agreement at -1.07 to 1.03. More than half the participants reported that the Internet version was easier to complete than the paper version (96% rated usability as 1 on a scale of 1-10, with 1 being extremely easy and 10 being impossible).

Conclusion: Assessment of disease severity by VAS may be accurately carried out over the Internet. This means that the evaluation of disease status and the longterm followup of people in different countries and perhaps in different languages may now be possible, using the Internet.