A multi-institutional study of interobserver agreement in the evaluation of dementia with rCBF/SPET technetium-99m exametazime (HMPAO).

Although specific patterns of technetium-99m exametazime [99mTc-hexamethylpropylene amine oxime (HMPAO)] brain single-photon emission tomography (SPET) uptake have been described for patients with dementia, no multi-institutional study has evaluated interobserver agreement. Interobserver agreement for 99mTc-HMPAO brain SPET uptake patterns in 50 clinically diagnosed demented subjects from four institutions were studied. Neurologists classified these subjects as presumed Alzheimer's disease (n = 21), confirmed Alzheimer's disease (n = 10), multi-infarct dementia (n = 9), HIV-related dementia (n = 7), or "mixed" (n = 3). In addition 20 normal (five per institution) 99mTc-HMPAO studies were included in a randomized blinded evaluation by three readers each from a different institution. Readers classified the general appearance of the images in one of four categories: normal, globally decreased uptake, focal areas of decreased uptake, and patchy changes in uptake. Consensus results show a sensitivity of 72% and specificity of 79% for identifying abnormalities in scans of demented subjects. Readers also rated 99mTc-HMPAO uptake in eight designated regions in each hemisphere. Significant reader agreement (P < 0.01) for the classification by general appearance and the ratings of regional uptake was obtained. This study demonstrates that interpretation of regional cerebral blood flow/SPET images is concordant across multiple institutions and readers.