Performance of response scales of Turkish version of activity and fuctional measures of ankylosing spondylitis: Numerical rating scale vs visual analog scale

ankylosing spondylitis: numerical rating scale vs visual analog scaleBackground: Bath ankylosing spondylitis disease activity index (BASDAI), Bathankylosing spondylitis functional index (BASFI) are frequently used self-reported measuresof disease activity and function in ankylosing spondylitis (AS) patients. Previously weshowed the validation of Turkish versions of these indices in their original answer modalities.Original response scales of these measures are 10-cm VAS however, it has been reported thatnumerical rating scale (NRS) is relatively simple and easy in application and scoring evenwhen administered verbally. Thus the aim of this study was to compare the performancecharacteristics of two answer modalities for BASDAI and BASFI in patients with AS and toshow validity and reliability of NRS in Turkish version.Methods: BASDAI and BASFI were simultaneously employed with a 10-cm VASand a 11-point NRS. Internal consistency was assessed by using intraclass correlationcoefficients (ICC). Testing was performed on baseline and next day under standardizedconditions.Baseline and next day data were used to assess test/retest reliability. Construct validity wasdetermined by association of these measures with ASDAS, global disease activity, painscores, ASQOL, HAQ, and SF-36. We also tested the ability of NRS version of BASDAI andBASFI to detect changes.Results: A total 114 patients with AS (87 [76%] male, mean age was 39.8 ± 10.9years) according to the modified New York criteria were included in the study. There wereperfect agreement between the total scores of BASDAI and BASFI and NRS and VASmodalities of each instrument on day 0 and day 1 and (ICC values were between 0.894-0.979). Scores of the both answering modality of each instrument were correlated with4ASDAS (CRP), and the scores of patient global assessment of disease activity and patientreported pain (VAS), ASQOL, HAQ. Response time for BASDAI and BASFI wassignificantly shorter in NRS answer modality on both day 0 and day 1 (p<0.005 for eachcomparison). Our patients has been found NRS modality easier to understand and answer(p<0.001). Also they reported that NRS was more preferable (p<0.001) than VAS.Conclusion: Our results showed the validity of NRS version of BASDAI and BASFIand provided an evidence for using these questionnaires in 11-point NRS answer modality inTurkish AS patients.