Impact of observer experience on the reproducibility of transient elastometry in HIV/HCV co-infected patients.

Background: Data on the influence of observer experience on transient elastometry (TE) in hepatitis C virus (HCV) infection are scarce, and there are no data on HCV/HIV co-infected patients. Methods: TE determination was conducted by an experienced and an inexperienced observer in 93 patients who were divided into three groups according to the chronological order of their attendance. The interobserver variability of TE results was analyzed by the intraclass correlation index (ICC) and the interobserver agreement of the classification of significant fibrosis and cirrhosis by the kappa index. Results: The overall ICC was 0.970 (95% confidence interval [CI] 0.954-0.980). For groups 1, 2, and 3, the ICCs were 0.952 (95% CI 0.901-0.977), 0.966 (95% CI 0.931-0.984), and 0.986 (95% CI 0.971-0.993), respectively. The kappa index for the classification of cirrhosis (cutoff value >= 14.6 kPa) for the three groups was 0.53, 1.00, and 0.91. The use of two cutoff points to exclude (<6 kPa) or diagnose significant fibrosis (>9 kPa) yielded a kappa index of 0.72, 1.00, and 1.00, respectively. Conclusions: In HIV/HCV co-infected patients, the concordance between an inexperienced and an experienced observer is acceptable after a short instruction period. To maximize this concordance, a training period of 60 measurements should be recommended.