F049 The effect of stimuli presentation on the distribution of stroop scores in enroll-HD

<h3>Objective</h3> To demonstrate the impact of stimuli presentation on scores from a paper-based administration of the Stroop task in Huntington’s disease (HD). <h3>Background</h3> The Stroop word reading and color naming conditions are tests of basic attention, and the interference condition is a test of response inhibition. For all three Stroop tests in Enroll-HD the total score indicates the number of items correctly completed in 45 seconds and the stimuli for each of the tasks are presented in a grid of 10 rows of 10 items in 3 colors (red, blue, and green) meant to be read horizontally. <h3>Methods</h3> We created histograms of the Stroop scores for persons with HD (pwHD; N = 18,900) (figure 1) and control participants (N = 5957) (figure 2). All participant visits were included in the distributions of scores, which were examined for the frequency of data points at each value, skewness, and outliers. <h3>Results</h3> The histograms for pwHD were shifted left compared to controls, an indication of lower scores on average for pwHD. Spiking of scores was evident at multiples of 10 for each task (e.g., 20, 30, 40, etc.) with the largest spike occurring at a value of 100 for the word reading condition. This suggests that participants stopped the test upon reaching the end of a line or, most frequently, the end of a page instead of continuing for the full 45 seconds. <h3>Conclusion</h3> Instructions should be clarified with participants for all Enroll-HD measures to prevent potential scoring irregularities.