Accuracy of DaTSCAN (123I-Ioflupane) SPECT in diagnosis of patients with clinically uncertain parkinsonism: 2-year follow-up of an open-label study.

We previously reported on the role of dopamine transporter (DAT) SPECT in the workup of patients with clinically uncertain parkinsonian syndromes (CUPS). The findings of that study supported the use of SPECT imaging with DaTSCAN ((123)I-Ioflupane) for accurate diagnosis in this population. We report here the 2-year follow-up of the CUPS study, which aimed to validate the results of DaTSCAN imaging and to ascertain whether a second scan could minimize any residual diagnostic uncertainty among those with an inconclusive diagnosis. Eighty-five of 118 patients (72%) were available at follow-up. In 8 of 85 patients the neurologist was unable to provide a definite diagnosis (named as inconclusive). At follow-up, clinical diagnosis agreed with initial DaTSCAN SPECT results in 69 of 77 patients (90%) in whom a specific diagnosis was established. A second SPECT scan was performed if clinical diagnosis at follow-up differed to that suggested by the initial scan (n = 8) or was inconclusive (n = 8). Among 8 patients whose clinical diagnosis differed to DaTSCAN images, a second scan was performed in 6 (2 refused) and the results supported the final clinical diagnosis in 4. Follow-up DaTSCAN SPECT helped to establish a diagnosis in 7 of 8 patients (87.5%) with a previously inconclusive diagnosis. DaTSCAN imaging shows a high rate of agreement with clinical diagnosis after 2-years follow-up. A second scan at 2 years follow-up can reduce remaining diagnostic uncertainty that is present even after a prolonged period of observation.