Increased neutrophil to lymphocyte ratio as a possible marker to detect neuroinflammation in patients with narcolepsy type 1.

Study objectives: Narcolepsy type 1 (NT1) is an autoimmune disease caused by the selective attack of orexin-producing neurons. However, the pathophysiology of narcolepsy type 2 (NT2) and idiopathic hypersomnia (IH) remains controversial. The neutrophil-to-lymphocyte ratio (NLR) is an easily calculated parameter from the white blood cell (WBC) count, which has already been extensively used as an inflammatory marker in immunological disorders. In this study, by examining the WBC counts of patients with NT1, NT2, and IH compared to controls, and evaluated the NLR to test the possibility of identifying an easy biofluid marker for detecting inflammation and distinguishing patients from healthy controls (HC).

Methods: WBC counts and NLR were compared in 28 NT1, 17 NT2, and 11 IH patients, in addition to 21 sex/age-matched HC. These parameters were correlated with cerebrospinal fluid (CSF) levels of orexin-A, the CSF/serum albumin ratio (as a marker of blood-brain barrier integrity), and polysomnographic parameters.

Results: NT1 (2.01±0.44) patients showed higher NLR than NT2 (1.59±0.53), IH (1.48±0.37), and HC (1.48±0.43), with no significant difference between NT2 and IH patients. The ROC curve analysis detected an optimal cut-off value to discriminate patients with NT1 from NT2, IH, and HC for values of NLR≥1.60, 1.62, 1.59, respectively.

Conclusions: Patients with NT1 showed a higher NLR than those with NT2, IH, and HC, possibly reflecting lymphocyte migration within the CNS, supporting the hypothesis of a neuroinflammatory attack of lymphocytes on orexin-producing neurons. Considering its sensitivity, this easily obtainable biofluid marker could help to screen NT1 patients.