The multi-inflammatory index (MII) is an effective mortality predictive biomarker among severely ill COVID-19 patients admitted to an intensive care unit (ICU). This was the conclusion of a retrospective study by a team of Turkish researchers.
Patients with severe COVID-19 often develop acute respiratory distress syndrome (ARDS), which represents a life-threatening form of respiratory failure. Soon after the infection has begun to take hold of an individual, neutrophils, which are a part of the innate immune system, rapidly infiltrate the lungs.
Another important immune cell is the lymphocyte, which plays a role in both immune homeostasis and inflammatory responses throughout the body. In fact, it has been observed that a depletion of these cells, known as lymphopenia, is an effective and reliable indicator of the severity and hospitalisation in COVID-19 patients.
Nevertheless, changes induced by COVID-19 are not restricted to these two cell types and there are many biochemical abnormalities produced, including elevation of inflammatory markers such as C-reactive protein in patients with severe disease, together with hyper-inflammation and a cytokine storm.
In fact, alterations in the level of several markers has been shown to be of value in predicting the prognosis of patients infected with the virus.
One particular biomarker, the multi-inflammatory index (MMI) includes the neutrophil to lymphocyte ratio (NLR) and C-reactive protein (CRP) levels. It was originally shown to have good shown to have good prognostic mortality value when examined in patients with metastatic colorectal cancer undergoing first-line chemotherapy.
Since researchers have identified that both the neutrophil-lymphocyte ratio and C-reactive protein are significantly higher in patients with COVID-19 who subsequently die, the Turkish team wondered if the MII – which includes both markers – would have prognostic value for identifying which critically ill patients with COVID-19, were at a higher risk of mortality.
The team retrospectively analysed data on COVID-19 patients admitted to an ICU and compared the prognostic value of MII with a range of inflammatory biomarkers combinations including the urea to albumin ratio, CRP to albumin ratio and the D-dimer to albumin ratio.
Multi-inflammatory index and COVID-19 mortality
A total of 348 patients with a median age of 74 years (59% male) were admitted to ICU due to COVID-19 and included in the analysis.
Overall, only 24.7% of patients survived and while co-morbidities such as hypertension, diabetes and COPD were numerically higher among those who died, these differences were not statistically different.
Using multiple logistic regression, among all the inflammatory measures used, only the MII was found to be an independent predictor of mortality (odds ratio, OR = 0.99, 95% CI 0.99 – 0.99, p = 0.03). Other significant predictors included age (OR = 1.07), the NLR (OR = 1.07).
Commenting on their results, the authors suggested that the likely reason why the NLR ratio was elevated in COVID-19 patients was because of an increased neutrophil count and a corresponding lymphopenia.
They concluded that MII represents a simple and practical biomarker that could help identify COVID-19 patients with a poor prognosis and called for further studies to validate these retrospective findings.
Citation
Gozdas HT et al. Multi-inflammatory Index as a Novel Mortality Predictor in Critically Ill COVID-19 Patients J Intensive Care Med 2022.
