Onodera's prognostic nutritional index: Comparison of its role in the severity and outcomes of patients with COVID-19 during the periods of alpha, delta and omicron variant predominance

Coronavirus disease 2019 (COVID-19) has posed a severe public health threat worldwide, affecting the function of multiple organs in affected individuals, in addition to respiratory function. Several strains of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been circulating worldwide since it first arose, with some of these having the ability to escape from natural or vaccine-mediated immunity. The Onodera's prognostic nutritional index (OPNI), which is derived from the peripheral lymphocyte count and serum albumin, has been reported to be significantly associated with a poor survival rate and post-operative complications in patients with various diseases and in some studies on patients with COVID-19. The aim of the present retrospective study was to evaluate and compare the efficacy of OPNI as a prognostic indicator in patients with COVID-19 during the periods of alpha, delta and omicron variant predominance. Adult patients who visited or were hospitalized due to SARS-CoV-2 infection were included, covering the second, third (alpha variant), fourth (delta variant) and fifth (omicron variant) pandemic waves. According to the results obtained, OPNI exhibited a statistically significant difference among patients with mild/moderate, severe and critical disease, with the lowest values observed in patients with critical disease in all the pandemic waves examined. Moreover, OPNI was found to be an independent prognostic biomarker of intubation and mortality in patients with COVID-19, according to multivariate logistic regression analysis, including as confounders an age >65 years, the male sex and the presence of comorbidities in all periods examined.