P50

Introduction: Reductions of cerebrospinal fluid (CSF) amyloid-beta(Aβ42) and elevated phosphorylated-tau(p-Tau) reflect in vivo Alzheimer's disease (AD) pathology and show utility in predicting conversion from mild cognitive impairment (MCI) to dementia. We investigated the P50 event related potential component as a non invasive biomarker of AD pathology in non-demented elderly.
Methods: 36 MCI patients were stratified into amyloid positive (MCI-AD, n=17)  and negative (MCI-Other, n=19) groups using CSF levels of Aβ42. All amyloid positive patients were also
p-Tau positive. P50s were elicited with an auditory oddball paradigm.
Results: MCI-AD patients yielded larger P50s than MCI-Other. The best amyloid-statuspredictor model showed 94.7% sensitivity, 94.1% specificity and 94.4% total accuracy.
Discussion: P50 predicted amyloid status in MCI patients, thereby showing a relationship with AD pathology versus MCI from an other etiology. The P50 may have clinical utility for
inexpensive prescreening and assessment of Alzheimer's pathology.

To describe the outcomes of subjects with suspected pre-psychotic state in Taiwan. A prospective clinical observation was performed on subjects recruited by referrals from a community-based population. Three pre-psychotic risk groups were established by means of clinical interviews: an ultra-high risk group (UHR; 59 subjects), an intermediate-risk group (IRG; 46 subjects), and a marginal-risk group (MRG; 48 subjects). Also recruited were 60 subjects with first-episode psychosis (FEP) and 144 normal controls (NC group). All subjects were aged 16 to 32 years. Of the 59 UHR subjects, 21 (35.6%) converted to FEP, including 15 with schizophrenia (6 had relatively brief positive yet persistent prominent negative symptoms), 2 with schizophreniform disorder, 1 with schizoaffective disorder, 2 with brief psychotic disorder, and 1 with bipolar disorder. The cumulative±SE rate of conversion to psychosis was 21.7%±5.4% at 6 months, 28.2%±6.2% at 12 months, 30.4%±6.4% at 18 months, and 33.3%±6.8% at 24 months. The UHR subjects who converted had a higher rate of initial antipsychotic use than those who did not convert. Only half of the IRG and two-thirds of the MRG subjects received follow-up, and none of them developed FEP. Our results lent support to both sides of the current debate regarding establishing a new diagnostic category of "psychosis risk syndrome." The divergent trajectories of the UHR subjects deserve more clinical attention, especially with regard to the use of antipsychotics and the presence of a group with prominent negative symptoms.