Poor inter-observer agreement on the TASC II classification of femoropopliteal lesions

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.

This is a validation study.

This study included 200 consecutive angiograms of femoropopliteal arterial lesions.

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.

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.

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.