Analyses of haptoglobin level in the cerebrospinal fluid and serum of patients with neuromyelitis optica and multiple sclerosis

Background: Neuromyelitis optica (NMO), which was previously considered a variant of multiple sclerosis (MS), is characterized by recurrent optic neuritis and longitudinally extensive spinal cord lesions. It has been shown that the level of haptoglobin in cerebrospinal fluid (CSF) is elevated in NMO. However, it is uncertain whether this change is specific to NMO, or is also seen in MS and other neurological diseases. Methods: We used an enzyme-linked immunosorbent assay (ELISA) to measure the haptoglobin levels in the CSF and serum in 25 NMO, 16 MS, and 15 Alzheimer's disease (AD) patients and 22 controls. Results: The CSF haptoglobin concentration of the NMO patients (0309 +/- 0.074 mg/dl, P<0.001) was significantly higher than that of MS patients (0.081 +/- 0.016 mg/dl) and AD patients (0.058 +/- 0.011 mg/dl), and the controls (0.060 +/- 0.009 mg/dl), whereas the serum haptoglobin and albumin concentrations in the serum and CSF did not differ significantly across groups. NMO patients (0.59 +/- 0.15, P = 0.001) demonstrated a higher haptoglobin index than MS patients (0.13 +/- 0.01), AD patients (0.12 +/- 0.03), and the controls (0.17 +/- 0.04). Furthermore, the haptoglobin concentration and haptoglobin index in the CSF correlated significantly with the expanded disability scale score (EDSS) in NMO patients. Conclusions: The high CSF haptoglobin concentration in NMO may be explained by increased intrathecal haptoglobin synthesis. The correlation between CSF haptoglobin concentration/haptoglobin index and EDSS highlights the potential of haptoglobin as a biomarker of NMO. (c) 2012 Elsevier B.V. All rights reserved.