The use of the comprehensive International Classification of Functioning, Disability and Health Core Set for low back pain in clinical practice: a reliability study

Background and Purpose. The comprehensive International Classification of Functioning, Disability and Health (ICF) Core Set for low back pain (LBP) can be used to describe functioning and the influence of the environment of patients with LBP with a selection of 78 categories, from the ICF components ‘body functions’, ‘body structures’, ‘activities and participation’ and ‘environmental factors’. The reliability of the qualifiers' scale of the ICF Core Set for LBP has not yet been studied. Methods. Reliability study was conducted in three study centres in the German‐speaking part of Switzerland. In the first step, two physiotherapists independently assessed 31 patients with LBP with the original qualifier scale of the 78 ICF categories from the comprehensive ICF Core Set for LBP. After the first 31 patients, inter‐rater reliability was assessed and the response options were reduced based on a Rasch analysis. The second sample (n = 30) was assessed by the physiotherapists with the modified qualifier scale and inter‐rater reliability was calculated again. Results. The percentage agreement for the ICF categories ranged from 19% to 87%, mean 44% (nominal kappa from −0.73 to 0.54, median 0.22; weighted kappa −0.2 to 0.69, median 0.38) in the first round with the original qualifier scale. In the second round with the reduced response options, the percentage agreement ranged from 23% to 90%, mean 49% (nominal kappa from −0.15 to 0.71, median 0.24; weighted kappa −0.16 to 0.81, median 0.25). The overall percentage agreement was 44% in the first round and 49% with the reduced response categories. The overall kappa value in the first round was 0.29 and in the second round 0.32. There was a small but statistically significant improvement in the agreement. Conclusion. The low‐to‐moderate reliability found in this study requires an improved operationalization (e.g. the definition and description of each response category) and improved instructions for the ICF Core Set for LBP. Copyright © 2009 John Wiley & Sons, Ltd.