PET-FDG TEST-RETEST RELIABILITY DURING A VISUAL-DISCRIMINATION TASK IN SCHIZOPHRENIA

Objective: Reliability of assessment is important in any kind of neuro psychiatric study, but is particularly pivotal in schizophrenia resear ch where symptom instability is common. Materials and Methods: Two flu orodeoxyglucose PET scans, 1 week apart, were carried out in schizophr enic patients while they were performing a simple visual discriminatio n task. Subject and scan conditions were held constant. Regional metab olic rates of glucose utilization were calculated as absolute and scal ed; they were compared using correlational statistics. Results: Averag e differences between scans were 5-9% for the parietal and occipital c ortices, but 1-3% for other cortical areas, differences comparable wit h reported variances in normal controls. Conclusion: These results sug gest that test-retest variance in metabolic imaging in schizophrenia i s relatively low and that task performance increases metabolic stabili ty in brain areas unrelated to task performance.