Comparison of Expert Reads vs. Local Clinical Reads of Amyloid PET Scans in IDEAS

Abstract

AbstractBackgroundAmyloid‐directed therapies will increase the clinical use of amyloid PET. IDEAS captured >17,000 clinical scan interpretations from local radiologists and nuclear medicine physicians. This study aimed to establish accuracy of these interpretations by comparison to expert readers across identical scans.MethodRandomly selected amyloid PET/CT scans performed using one of three FDA‐approved agents [18F‐Florbetaben (FBB), 18F‐Florbetapir (FBP), 18F‐Flutemetamol (FMM)] and previously interpreted by local readers from the Imaging Dementia ‐ Evidence for Amyloid Scanning (IDEAS) study were assigned to vendor‐selected panels of 3 expert readers for interpretation; 500 scans per agent and 1 panel per agent. Scans were stratified to match frequencies observed in the overall study by 1) participant age; 2) MCI vs dementia; 3) positive/negative interpretation; and 4) type of PET facility. Respective vendors performed quality control on attenuation‐corrected PET/CT images. Visual interpretations (positive or negative for Aß cortical deposition) were performed according to agent‐specific validated interpretation criteria. Expert panel readers were blinded to clinical and demographic data. Cohen’s kappa statistic with two‐sided 95% confidence interval estimates examined agreement between local reader and majority expert panel visual interpretation.ResultExpert panel readers’ visual interpretations totaled 4489. Median age for scanned participants was 75 (range 65‐96), 51.4% were female and 60.5% had MCI. Local readers interpreted 60.9% of scans positive and 39.1% negative (Table 1). Across all radiotracers, agreement between majority expert read and local readers was excellent (k coefficient 0.76; 95% CI 0.73 – 0.80, p<.0001) with 86.6% (791/913) agreement for positive scans and 90.9% (532/585) agreement for negative scans (Figure 1). Agreement by individual radiopharmaceuticals was good to excellent: k coefficient 0.78 (95% CI 0.72 – 0.83, p<.001) for FBB, k coefficient 0.72 (95% CI 0.66 – 0.78, p<.001) for FBP, and k coefficient 0.78 (95% CI 0.73 – 0.84) for FMM (Figure 1). Agreement levels between local readers and individual experts varied from good to excellent (Figure 2).ConclusionWe found good to excellent agreement between local readers and majority assessment of three‐member expert panels for all combined scans and scans by individual agents. Visual interpretation of Aß PET can be performed in a clinical setting with high reliability.