A MULTIINSTITUTIONAL STUDY OF INTEROBSERVER AGREEMENT IN THE EVALUATION OF DEMENTIA WITH RCBF SPET TC-99M EXAMETAZIME (HMPAO)/

Although specific patterns of technetium-99m exametazime [Tc-99m-hexam ethylpropylene amine oxime (HMPAO)] brain single-photon emission tomog raphy (SPET) uptake have been described for patients with dementia, no multi-institutional study has evaluated interobserver agreement. Inte robserver agreement for Tc-99m-HMPAO brain SPET uptake patterns in 50 clinically diagnosed demented subjects from four institutions were stu died. Neurologists classified these subjects as presumed Alzheimer's d isease (n=21), confirmed Alzheimers's disease (n=10), multi-infarct de mentia (n=9), HIV-related dementia (n=7), or ''mixed'' (n=3). In addit ion 20 normal (five per institution) Tc-99m-HMPAO studies were include d in a randomized blinded evaluation by three readers each from a diff erent institution. Readers classified the general appearance of the im ages in one of four categories: normal, globally decreased uptake, foc al areas of decreased uptake, and patchy changes in uptake. Consensus results show a sensitivity of 72% and specificity of 79% for identifyi ng abnormalities in scans of demented subjects. Readers also rated Tc- 99m-HMPAO uptake in eight designated regions in each hemisphere. Signi ficant reader agreement (P<0.01) for the classification by general app earance and the ratings of regional uptake was obtained. This study de monstrates that interpretation of regional cerebral blood flow/SPET im ages is concordant across multiple institutions and readers.