Background PBA-s is a core assessment in ENROL, the largest observational study in Huntington disease. It is recommended that the PBA-s be administered in any study where an intervention, pharmacological or not, is performed that could cause changes in behaviour. Despite this fact, this instrument is not yet validated into Spanish. Considering the Spanish speaking population all over the world, validating this assessment tool is extremely important in HD.

Aim Validate the PBA- s into Spanish to dispose of an extremely important evaluation tool in Huntington disease subjects.

Methods/techniques The validation process includes: direct translation, back translation, pilot testing of the consensus version and cognitive debriefing. After completing this process, we have a final consensus Spanish PBA-s version (Spa. PBA-s)

We carried out a statistical analysis of Inter- and Intra-rater reliability measured by the Inter-class Correlation Coefficients (ICC).

Results/outcomes We present preliminary results: 70 subjects (42 women, 28 men) age: mean 48.24 y. (SD 12.94) were assessed. 7.1% were at risk individuals, 8.6% asymptomatic carriers, 64.3% manifest HD, 20% controls. TFC: stage I: 27.1%; II: 8.6%; III: 15.7%; IV: 24.3%; V: 4.3%. This sample represents the 63.6% of the sample required (110 individuals).

Reliability of Inter-rater severity scores are good, with an ICC between 0.886 and 0.979 (n = 25); Intra-interview show ranges from 0.977 to 1.000 (n = 15). Frequency Inter- and Intra-rater also were good with scores from 0.820 to 0.991. (Inter: n = 25; Intra: n = 15).

Conclusions The PBA-s Spanish version demonstrates in these preliminary results a very good reliability. Although our preliminary results show better inter and inter-rater reliability that reported in previous studies, it is necessary to achieve the complete sample to conclude it.