Observer reproducibility of results from a low-dose 123I-metaiodobenzylguanidine cardiac imaging protocol in patients with heart failure

Imaging of the cardiac autonomic system with I-123-metaiodobenzylguanidine (MIBG) is useful in the evaluation of patients with a variety of cardiac conditions, including heart failure (HF), but few data are available about the reproducibility of this technique. We assessed the observer reproducibility of the results from a low-dose I-123-MIBG cardiac imaging protocol in patients with HF. A total of 74 patients (62 men, age 67 +/- 10 years) with HF and left ventricular systolic dysfunction (ejection fraction 31 +/- 7 %) underwent low-dose (111 MBq) planar and single-photon emission computed tomography (SPECT) I-123-MIBG cardiac sympathetic imaging. The intraclass coefficient of correlation (ICC), Lin's concordance correlation coefficient, and Bland-Altman analysis were used to evaluate the intraobserver and interobserver reproducibility of early and late heart-to-mediastinum (H/M) ratios and of defect scores on SPECT images. The kappa statistic was used to evaluate the concordance rates for the identification of patients with a low H/M ratio (< 1.60) on late planar imaging. The differences between measurements obtained twice by the same examiner and by two examiners were negligible for both early and late H/M ratios and for SPECT defect scores. These findings were confirmed by the results of Bland-Altman analysis, and ICC and Lin's coefficient values were excellent (> 0.90) for all measurements. For the identification of patients with a low H/M ratio, the kappa values were 0.90 for intraobserver concordance and 0.83 for interobserver concordance. The present study showed a high observer reproducibility of planar H/M ratios and SPECT defect scores using a low-dose I-123-MIBG cardiac imaging protocol in patients with HF.