Psychometric properties of the bath ankylosing spondylitis disease activity index (BASDAI): comparison of the different versions available in English.
OBJECTIVE
International ASAS consensus statement proposed the use of the BASDAI to evaluate active disease in ankylosing spondylitis patients before the use of anti-TNF agents. To analyze the psychometric properties of the different versions of the BASDAI.


METHODS
All versions available in English were analyzed according to the methods developed by the American Psychological Association. Except for the initial version, the procedure of translation was accepted if a translation followed by a back translation was carried out. The psychometric properties analyzed were: face validity, content validity, construct validity (factorial analysis, convergent and divergent validity), reliability (test retest, Cronbach's coefficient alpha), and responsiveness.


RESULTS
Except for the German version which was not available in English, the following versions were analyzed: English (En), French (Fr), Swedish (Sw), Spanish (Sp), and Turkish (Tu). The procedure translation was correct in all the versions without taking into account the initial En version. Face validity was validated in all versions. No version initially defined the dimensions for the content validity. Construct validity was partially studied and validated in En, Fr and Sp. Reliability was validated in En, Fr, Tu, and partially in other versions. In all versions, except for the Fr, responsiveness was demonstrated.


CONCLUSIONS
The English version of the BASDAI is the most validated tool. Some efforts had to be made to continue the validation procedure of all versions of the BASDAI. This is an important step for further international comparison.
Maravic
M
M
Hôpital Necker Enfants Malades (APHP), Service de Biostatistique et Informatique Médicale, Paris, France. milka-maravic@noos.fr
Fermanian
J
J
D003431:Cross-Cultural Comparison; D006801:Humans; D011594:Psychometrics / Q000379:methods / Q000592:standards; D012720:Severity of Illness Index; D013167:Spondylitis, Ankylosing / Q000175:diagnosis / Q000503:physiopathology / Q000523:psychology*