Shortening the Leuven Perceptual Organization Screening Test with item response theory and confirmatory factor analysis.

The Leuven Perceptual Organization Screening Test (L-POST) is a test for midlevel visual perceptual deficits after brain injury. Previous research demonstrated reliable test scores and valid test score interpretations. However, the test's duration (20-35 min) is too long for a screening approach for all patients in clinical practice. Our aim was to shorten L-POST to 10-15 min based on statistical criteria of the items. Data from 3,391 participants who completed L-POST were analyzed. L-POST consists of 15 subtests with five items each. Item Response Theory (IRT) was applied to guide the selection of the items. The highest correlation with full-scale subtest scores was observed when two items were selected for each subtest following an adaptive testing procedure. A pilot validation in a subsample of participants with low abilities demonstrated adaptive testing has reasonable sensitivity (80%) but limited specificity (55%) in classifying participants with impaired and unimpaired abilities. Subsequently, we reduced the number of subtests through factor analysis. We showed that the subtests using Radial Frequency Patterns as stimuli were redundant and could be combined in one subtest. We conclude that L-POST can be shortened to 26 items (7-14 min) and an adaptive item selection procedure could prove particularly useful for screening purposes. (PsycInfo Database Record (c) 2021 APA, all rights reserved).