Comparison of the diagnostic performance of H/M ratio between early and delayed phases for Lewy body disease

OBJECTIVES The aim of the study was to compare the diagnostic performance of early-phase I-metaiodobenzylguanidine (MIBG) scintigraphy with that of delayed-phase imaging in Lewy body disease (LBD). METHODS A retrospective cohort study of ¹²³I-MIBG scintigraphy was carried out in 192 patients who were suspected of having LBD. Clinical diagnosis was obtained using the UK Parkinson's Disease Brain Bank Criteria in some cases or the third report of the Dementia with Lewy bodies Consortium in others. The participants consisted of 81 patients with LBD and 111 nondiseased patients. An injection of 111 MBq of ¹²³I-MIBG was used. Planar images were obtained in an early phase and again in a delayed phase and the heart to mediastinum count ratio was calculated for both phases. Diagnostic performance was compared using a receiver-operator characteristic analysis. The cutoff value was chosen to maximize the Youden index. The sensitivity and specificity of each phase were calculated from the optimal cutoff value. RESULTS The heart to mediastinum ratio of the LBD group (median 1.8 and 1.45 for early and delayed phases, respectively) was significantly lower than that of the nondiseased group (median 2.93 and 3.18 for early and delayed phases, respectively). The area under the receiver-operating characteristic curve was not significantly different between the early and delayed phases (0.871 vs. 0.893; P=0.0914). Sensitivity and specificity were 80.2 and 91% for early-phase imaging (cutoff value at 2.28) and 81.5 and 95.5% (cutoff value at 1.91) for delayed-phase imaging, respectively. CONCLUSION The diagnostic performance of ¹²³I-MIBG scintigraphy was not significantly different between early-phase and delayed-phase imaging.