To investigate whether serum AD biomarkers enhance accuracy of the German version of the Dementia Screening Questionnaire for Individuals with Intellectual Disabilities (DSQIID-G), we combined test scores with neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) levels.<h4>Methods</h4>Seventy-eight DS individuals (49% female) completed the DSQIID-G; previous cohort data were added for a pooled sample (n = 164, 47% female). This evidence concerns the gene NEFL and Intellectual disability.