17,36 The low CSF Aβ1-42 levels in the non-AD dementia group may partly be explained by comorbid Aβ pathology (3 of 4 cases in this group with CSF Aβ1-42 levels below the threshold also had intermediate or high A scores) but also may be affected by other pathologic or physiologic factors known to influence CSF Aβ1-42 levels.27,37 In both diagnostic contexts, the discriminative accuracy could be slightly improved with the use of the CSF tau-to-Aβ1-42 ratios. The gene discussed is MAPT; the disease is Alzheimer disease.