Poor Inter-observer Agreement on the TASC II Classification of Femoropopliteal Lesions

Objectives: This study aims to evaluate the reproducibility of femoropopliteal TASC II classification and to analyse the influence of an educational intervention on inter-observer agreement. Design: This is a validation study. Materials: This study included 200 consecutive angiograms of femoropopliteal arterial lesions. Methods: Seven investigators evaluated the first 100 angiograms, independently aided by the available TASC guide. Thereafter, the intervention included a discussion of the 25 most problematic cases, initially by a panel of 22 vascular surgeons, and later by the seven investigators to clarify grading principles. In the second stage, the 100 remaining cases were evaluated independently. A multi-rater variation of Brennan and Prediger's free-marginal kappa (kappa(free)) was used to calculate inter-observer agreement. Results: There were lesions not fitting any of the TASC classes. Total agreement among all seven investigators was reached in 7% and 19% of the cases before and after the intervention, respectively. In the first stage, kappa(free) was 0.32 between all observers (range between two observers kappa(free) = 0.11-0.54). The intervention increased the agreement to kappa(free) = 0.49 (range: 0.20-0.56). Agreement between the two observers was 38-69% (mean 49%) before the intervention and 51-73% (mean 61%) thereafter. Conclusions: TASC II classification for femoropopliteal lesions allows individual interpretations, and the common use of this classification as a basis for decision making and reporting outcomes could therefore be questioned. (C) 2009 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.