Use of cerebrospinal fluid amyloid-beta and total tau protein to predict favourable surgical outcomes in patients with idiopathic normal pressure hydrocephalus

Object The prognostic value of CSF biomarkers in patients with idiopathic normal pressure hydrocephalus (iNPH) has not been adequately studied to date. The aim of this study was to identify CSF markers of favorable surgical outcome in patients with iNPH undergoing the insertion of a ventriculoperitoneal shunt. Methods Ventricular CSF was collected intraoperatively from 22 patients with iNPH and enzyme-linked immunosorbent assay was used to analyze the levels of amyloid-β 1-42 (Aβ(1-42)) and total tau protein. The Black grading scale was used to assess outcomes at 6 months. Receiver operating characteristic (ROC) curves were obtained and discriminant function analysis was undertaken to provide sensitivity and specificity figures for each marker as well as their combination. Results The mean age of the patients was 71.45 years (± 9.5 years [SD]). Follow-up was achieved in 21 patients. Seventeen patients had a favorable outcome and 4 patients had unfavorable outcome at 6 months. An Aβ(1-42) level of 180 pg/ml had a sensitivity of 35% and a specificity of 20% for predicting a favorable outcome at 6 months. A total tau level of 767 pg/ml will have a sensitivity of 17% and a specificity of 20% for predicting a favorable outcome at 6 months. A combination of Aβ(1-42) and total tau levels predicted favorable outcomes with a sensitivity of 80% and specificity of 82.4%. Conclusions In this pilot study a combination of Aβ(1-42) levels and total tau protein levels predicted favorable surgical outcomes at 6 months with adequate accuracy to be of clinical use. Further study in a larger group with longer follow-up is warranted.