THE DIAGNOSTIC-VALUE OF SPECT WITH TC-99M HMPAO IN ALZHEIMERS-DISEASE- A POPULATION-BASED STUDY

We studied the diagnostic accuracy of single-photon emission computed tomography (SPECT) with technetium 99m-labeled hexamethylpropylene ami ne oxime (Tc 99m HMPAO) in 48 patients with probable Alzheimer's disea se (AD) according to NINCDS-ADRDA criteria and in 60 controls recruite d from a population-based study. With logistic regression, we identifi ed decreased temporal regional cerebral blood flow as the best discrim inating variable between patients and controls. Receiver-operator char acteristic curves showed that the discriminative ability of SPECT impr oved with increasing dementia severity. With specificity set at 90%, s ensitivity figures were 42% in mild, 56% in moderate, and 79% in sever e AD. The diagnostic gain as a function of the prior probability of th e disease being present was computed for those with mild AD. When the prior probability varied at around 50%, the diagnostic gain for mild A D patients was substantial (a maximum of 34%) for a positive test resu lt but poor for a negative test result. The results suggest that the p ractical usefulness of SPECT as a diagnostic adjunct in patients suspe cted of having mild AD is confined to situations in which, on clinical grounds, there is considerable diagnostic doubt.