O6.5. INVESTIGATING VARIABLES FROM THE NAPLS RISK CALCULATOR FOR PSYCHOSIS IN THE EU-GEI HIGH RISK STUDY

Abstract Background Individuals at clinical high risk (CHR) for psychosis have approximately a 25% chance of transitioning to psychosis in the first 2 years after first presentation to clinical services. A key aim in this field is to determine the risk of conversion for an individual meeting the criteria for CHR based on clinical, demographic and neuropsychological measures. An individualized risk calculator incorporating 8 risk factors based on these measures has recently been developed by the researchers from the North American Prodrome Longitudinal Study (NAPLS-2) and tested in their dataset of CHR participants. Methods We examined the risk factors from the NAPLS risk calculator in the EU-GEI (EU funded gene environment interaction) high risk study. The EU-GEI high risk study is a longitudinal multi-centre study including 9 sites in Europe, 1 site in Australia and 1 site in Brazil. At baseline, the study included 345 CHR individuals of which 65 later developed psychosis. The NAPLS risk calculator includes 8 risk factors and for each risk factor we attempted to harmonise the EU-GEI measures to the corresponding NAPLS measure. We used multivariate cox regression to determine the standardised hazard ratio for transition to psychosis for the 8 risk factors. To compare each of the NAPLS and EU-GEI hazard ratios we used a meta-analytical framework to calculate a combined hazard ratio and to examine heterogeneity between the effect sizes. Results In terms of the 8 risk factors, only the CAARMS unusual thought + non-bizarre ideas (corresponding to NAPLS SIPS P1+P2) was significantly associated with transition to psychosis, standardised hazard ratio = 1.51 (95%CI 1.01–2.23), p=0.046. Hazard ratios for the remaining risk factors varied from 0.73 to 1.41. The meta-analysis combining EU-GEI and NAPLS data did not indicate heterogeneity for any of the 8 measures, suggesting no systematic differences in the risk factors between the two studies. Discussion The test of the NAPLS risk factors in the independent EU-GEI high risk sample showed support for unusual thought content and non-bizarre ideas being predictive of later transition to psychosis. We were not able to replicate decline in functioning and lower scores in verbal learning memory as predictive of transition to psychosis as seen in the NAPLS study. However, our meta-analytical comparison showed no systematic differences in the hazard ratios for all 8 risk factors between both studies suggesting broad compara