NLR immune cell ratio may be NMOSD inflammation biomarker
Greater neutrophil-to-lymphocyte difference seen in people with the disease
People with neuromyelitis optica spectrum disorder (NMOSD) have a significantly higher neutrophil-to-lymphocyte ratio (NLR), an immune cell-based marker of inflammation, than healthy people, a review study showed.
A higher NLR ratio was also significantly associated with a greater chance of relapse, severe disability, and new or enlarging lesions on a MRI, but with variable levels of certainty.
The findings suggest NLR, “whose values are easy and inexpensive to obtain,” could help distinguish NMOSD patients from healthy people and work as a prognostic biomarker of the autoimmune disease, the researchers wrote in the study, “Clinical and imagenologic significance of the neutrophil-to-lymphocyte ratio in neuromyelitis optica spectrum disorder: A systematic review with meta-analysis,” which was published in PLOS One.
NMOSD is a progressive autoimmune disease wherein the immune system mistakenly attacks cells from the nervous system, primarily causing inflammation of the optic nerve — the nerve that transmits signals between the eye and brain — and the spinal cord. Episodes of inflammation reoccur periodically, followed by periods of remission.
The inflammatory reaction in NMOSD is “characterized by the presence of neutrophils, eosinophils and macrophages in high proportion but lymphocytes in small proportion,” the researchers wrote.
The first three are the immune system’s first responders to infection or injury, triggering inflammation, while lymphocytes are mostly involved in slower and threat-specific immune responses. Several previous studies have implicated neutrophils in NMOSD.
The neutrophil-to-lymphocyte ratio, a well-established marker of inflammation, has been suggested as a predictive blood biomarker of the course of certain neurological conditions, such as stroke.
NLR’s potential as biomarker in NMOSD
Researchers in Peru retrospectively analyzed studies published up to December 2021 that evaluated the ratio’s biomarker potential in NMOSD.
Six retrospective studies involving 806 NMOSD adult patients and 721 healthy people were included in the meta-analysis. The average age for patients was between 36-48.
Pooled data from three studies, including 382 NMOSD patients and 654 healthy controls, showed that the mean NLR was significantly higher in patients. Comparable findings were seen in a subgroup analysis of matched patients and controls. Similar results were reported in previous studies of other autoimmune diseases such as multiple sclerosis, and lupus, the researchers noted.
A higher NLR can differentiate NMOSD patients from healthy people with high certainty, analysis suggested.
The prognostic value of NLR was evaluated in two of the included studies comprising 414 NMOSD patients who were followed from two to more than 3.5 years.
Both studies reported a significant link between a high NLR and a greater likelihood of a disease relapse — from 33% to two times more. These conclusions were classified as having low certainty based on imprecision and inconsistency in the studies, however.
One study reported that patients with a high NLR had a significantly higher chance (by 23%) of having relatively severe disability. The other study found a significant association between high NLR and a 52% greater likelihood of having new or enlarging lesions on a MRI. Both links were consider of moderate certainty.
These findings “revealed a higher NLR average in NMOSD patients than in healthy controls with high certainty,” and that “patients with poor long-term prognoses (NMOSD relapse, moderate incapacity, and new lesions on MRI) had higher NLR values than those who had better results,” the researchers wrote.
“Our results indicate that the NLR could serve to both differentiate NMOSD patients from healthy patients and indicate poor long-term prognosis. NLR gains clinical importance since it is derived from tests that are simple to perform, inexpensive, and routinely available, and can be used in conjunction with other clinical or laboratory variables to generate valid predictive models,” they said, adding larger studies should be conducted that followed patients over time and that included populations from other regions and ethnic groups to account for differences in the disease’s prevalence.