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Prognostic Significance of NLR and PLR in COVID-19: A Multi-Cohort Validation Study
Marta Colaneri1,2, Camilla Genovese3, Federico Fassio4
1Department of Infectious Diseases, Luigi Sacco Hospital, ASST Fatebenefratelli Sacco, Milan, Italy.
Insights
Neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) effectively predict severe outcomes in COVID-19 patients. High negative predictive values (NPVs) confirm their utility in identifying individuals with a lower likelihood of severe disease progression.
Area of Science:
- Medical research
- Clinical diagnostics
- Inflammatory markers
Background:
- Recent studies indicate prognostic value of neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) for severe COVID-19 outcomes.
- Validation of established NLR and PLR cut-off values across new cohorts is crucial for generalizability.
Purpose of the Study:
- To validate previously determined neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) cut-off values in new COVID-19 patient cohorts.
- To assess the generalizability of NLR and PLR as prognostic indicators for severe COVID-19 outcomes.
Main Methods:
- Retrospective cohort study involving 3599 COVID-19 patients across two hospitals.
- Assessed predictive capacity of NLR and PLR for non-invasive ventilation (NIV)/CPAP, invasive ventilation (IV), and death.
- Calculated sensitivity, specificity, PPV, and NPV separately for male and female cohorts using established cut-off values.
Main Results:
- Sensitivity values for NLR and PLR were lower than specificity values across cohorts.
- Positive predictive values (PPVs) were generally below 63%, while negative predictive values (NPVs) exceeded 68% for PLR and 72% for NLR.
- NLR and PLR demonstrated higher NPVs for severe outcomes (e.g., death, IV) compared to NIV/CPAP usage.
Conclusions:
- Findings confirm the reliability and applicability of NLR and PLR cut-off values across diverse populations.
- High NPVs highlight the utility of NLR and PLR in identifying patients at lower risk of severe COVID-19.
- These inflammatory markers aid in risk stratification and resource allocation during public health emergencies.
Introduction:
Recent studies have highlighted the prognostic value of easily accessible inflammatory markers, neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR) for predicting severe outcomes in patients affected by Coronavirus disease 2019 (COVID-19). Our study validates NLR and PLR cut-off values from a prior cohort at IRCCS Policlinico San Matteo (OSM) of Pavia, Italy, across two new cohorts from different hospitals. This aims to enhance the generalizability of these prognostic indicators.
Methods:
In this retrospective cohort study, conducted at Milan's Ospedale Luigi Sacco (OLS) and IRCCS Ospedale Maggiore Policlinico (OMP) hospitals, we assess the predictive capacity of NLR and PLR for three main outcomes-non-invasive ventilation (NIV) or continuous positive airway pressure (CPAP) usage, invasive ventilation (IV), and death-in patients with COVID-19 at admission. For each outcome, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were computed separately for male and female cohorts. Distinct NLR and PLR cut-off values were used for men (7.00, 7.29, 7.00 for NLR; 239.22, 248.00, 250.39 for PLR) and women (6.36, 7.00, 6.28 for NLR; 233.00, 246.45, 241.54 for PLR), retrieved from the first cohort at OSM.
Results:
A total of 3599 patients were included in our study, 1842 from OLS and 1757 from OMP. OLS and OMP sensitivity values for both NLR and PLR (NLR: 24-67%, PLR: 40-64%) were inferior to specificity values (NLR: 64-76%, PLR: 55-72%). Additionally, PPVs generally remained lower (< 63%), while NPVs consistently surpassed 68% for PLR and 72% for NLR. Finally, both PLR and NLR exhibited consistently higher NPVs for more severe outcomes (> 82%) compared to NPVs for CPAP/NIV.
Conclusions:
Consistent findings across diverse patient populations validate the reliability and applicability of NLR and PLR cut-off values. High NPVs emphasize their role in identifying individuals less likely to experience severe outcomes. These markers not only aid in risk stratification but also guide resource allocation in emergencies or limited-resource situations.
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