Only a limited number of the identified instruments for the assessment of impairments is both reliable and valid .
The objective of this study is to provide a critical overview of available instruments to assess impairments in patients with rheumatic disorders , and to recommend reliable and valid instruments for use in allied health care and rehabilitation medicine .
Use of a numerical rating scale as an answer modality in ankylosing spondylitis-specific questionnaires.
OBJECTIVES To determine the agreement of scores on the original visual analog scale ( VAS ) or Likert scale of the Bath Ankylosing Spondylitis Disease Activity Index ( BASDAI ) , Bath Ankylosing Spondylitis Functional Index ( BASFI ) , and Dougados Functional Index ( DFI ) with scores on a numerical rating scale ( NRS ) . To assess the reproducibility and responsiveness of the instruments with the original scale and NRS . METHODS Five hundred thirty-six patients with ankylosing spondylitis from the Netherl and s , Mexico , and Switzerl and completed a question naire  in which all questions from the BASDAI , BASFI , and DFI were presented twice in r and om order with an 11-point NRS and either a 10-cm VAS ( BASDAI and BASFI ) or a 5-point Likert scale ( DFI ) . Agreement of scores using Bl and -Altman plots and intraclass correlation coefficients ( ICCs ) , reproducibility using ICCs , and responsiveness were assessed . RESULTS Large variability between the scores on the original scales and the NRS was found in individual questions of all 3 question naires , although total scores showed ICCs of at least 0.88 . Reproducibility of all answer modalities showed low ICCs in individual questions , but moderate to good ICCs in total scores ( Dutch group 0.62 - 0.89 ; Mexican group 0.53 - 0.72 ) . Moderate to large effects ( 0.48 - 1.04 ) were found in responsiveness scores in the 3 question naires . No major differences in reproducibility and responsiveness between the answer modalities were found . CONCLUSION Although large variability between the scores on the original answer scales and the NRS was observed , the BASDAI , BASFI , and DFI can be administered with an NRS , which does not show important differences compared with the original scales
Only a limited number of the identified instruments for the assessment of impairments is both reliable and valid .
The objective of this study is to provide a critical overview of available instruments to assess impairments in patients with rheumatic disorders , and to recommend reliable and valid instruments for use in allied health care and rehabilitation medicine .