Prothrombin concentration in the cerebrospinal fluid is not altered in Alzheimer's disease

Prothrombin, known to be expressed in brain and to possess growth modulating properties, has been suggested to be involved in the pathogenesis of Alzheimer's disease (AD). We studied prothrombin concentration in lumbar CSF (L-CSF) in patients with AD (n = 25), neurologic disease controls (NDC; n = 33) covering a wide range of neurologic disorders, and subjects with Guillain-Barre syndrome (GBS; n = 4) as well as in samples of non-pathological ventricular CSF (V-CSF; n = 4). The results were evaluated with respect to CSF flow rate, as indicated by the albumin quotient (QAlb). The concentrations of prothrombin in L-CSF in NDC (mean: 0.46 mg/l, range: 0.21–0.96), and AD (mean: 0.6 mg/l, range: 0.19–1.2) were in the normal range reported previously. Expectedly, prothrombin concentration in L-CSF of GBS was increased (mean: 6.3 mg/l, range: 2.3–9.7) corresponding to the increased QAlb in this group (mean 54.6 × 10−3, range: 17–88.1). The concentrations of both prothrombin and albumin were 5.5-fold higher in L-CSF than in V-CSF (mean QAlb : 1.1 × 10−3, mean concentration of prothrombin: 0.088 mg/l). In conclusion, CSF prothrombin in all conditions evaluated here is exclusively derived from blood.