Neutrophil to Lymphocyte Ratio and Its Association to COVID-19 Delirium

Background and/or Objectives: To explore the relationship of neutrophil-to-lymphocyte ratio (NLR) with COVID-19 delirium prevalence and outcomes, as well as other potential predictors of COVID-19 delirium.

Design: Initial data set included 400 patients admitted to acute inpatient rehabilitation with COVID-19 from March 2020 to April 2021. 106 patients opted out of research. Of this remaining set, there were 133 patients excluded due to pre-existing cognitive changes or incomplete data. Of the remaining patients, 94 patients met the above criteria and had available data from the Confusion Assessment Method for the ICU (CAM-ICU).

Setting: Acute inpatient rehabilitation at a free-standing inpatient rehabilitation facility.

Participants: 94 patients with COVID-19 delirium secondary to COVID-19 infection. These patients participated in acute inpatient rehabilitation.

Interventions: not applicable

Main Outcome Measures: NLR in delirium-positive vs delirium-negative COVID-19 patients, NLR as predictor of rehabilitation outcomes, NLR and association with Brief Interview for Mental Status (BIMS), BIMS association with disability on rehabilitation discharge.

Results: NLR was higher in the non-delirium group than in the delirium group (F[1,82]=4.86 (p=.03)). NLR also decreased overall with time as expected (F[1,82]=12.75 (p=.001). However, there was not a statistically significant difference in the overall rate of decrease of NLR in delirium patients when compared to those without delirium.

Conclusions: NLR has been studied as a prognostic factor in COVID-19 outcomes. In our study, NLR had a negative correlation with the presence of delirium in COVID-19 patients and was noted to be lower in patients with COVID-19 delirium. In individual cases, there were noted acute spikes in NLR correlating with the onset of delirium. We have reported elsewhere that on discharge, patients with COVID-19 delirium had improved functional outcomes when compared to those without delirium. There may be multiple mechanisms contributing to the onset of COVID-19 delirium. Further exploration is needed.