Increased plasma levels of chitinase 3-like 1 (CHI3L1) protein in patients with idiopathic normal-pressure hydrocephalus

Idiopathic normal-pressure hydrocephalus (iNPH) is an uncommon neurological disorder with no known pathological hallmarks. INPH may share common degenerative pathways with other neurological diseases, such as Alzheimer's disease (AD). However, the reversible properties of iNPH may share differing pathophysiological mechanisms with other diseases. This study aimed at assessing the diagnostic value of plasma chitinase 3-like 1 (CHI3L1) protein levels as a disease-specific biomarker for iNPH. We selected both iNPH and AD patients as well as normal and disease control subjects from an enrolled dementia registry. A total of 121 AD, 80 iNPH, 13 idiopathic Parkinson's disease, and 23 mild cognitive impairment patients with 83 healthy controls were included in the final analysis. The Aβ42, total tau, and phosphorylated tau levels within the cerebrospinal fluid, as well as plasma levels of CHI3L1, were measured using commercially available enzyme-linked immunosorbent assay kits. CHI3L1 levels for iNPH patients were higher than those of the other groups. Analysis of covariance adjusting for age showed significantly increased plasma CHI3L1 levels in iNPH patients than in the controls (p < 0.001). CHI3L1 plasma levels may be useful in differentiating iNPH patients from healthy individuals.