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Platelet-to-Lymphocyte Ratio-A Real or Fake Bridge Between Inflammation and Coagulation in COVID-19 Patients: A
Maja Aleksandra Oksentowicz1, Maria Sztachelska2, Violetta Dymicka-Piekarska1
1Department of Clinical Laboratory Diagnostics, Medical University of Bialystok, 15-089 Bialystok, Poland.
Insights
The platelet-to-lymphocyte ratio (PLR) may indicate COVID-19 severity and mortality risk. While not a direct marker for COVID-19-Associated Coagulopathy (CAC), higher PLR is linked to worse outcomes, aiding clinical assessment.
Area of Science:
- Hematology
- Infectious Diseases
- Critical Care Medicine
Background:
- COVID-19-Associated Coagulopathy (CAC) involves an imbalance in coagulation pathways due to SARS-CoV-2 infection.
- The platelet-to-lymphocyte ratio (PLR) is a hematological parameter reflecting inflammation and platelet/lymphocyte counts.
Purpose of the Study:
- To investigate the prognostic value of the platelet-to-lymphocyte ratio (PLR) in predicting COVID-19 severity and mortality.
- To analyze the diagnostic utility of PLR using Receiver Operating Characteristic (ROC) curve analysis.
Main Methods:
- A systematic literature search was conducted on PubMed for studies published between 2020-2025.
- Twenty studies evaluating the prognostic value of PLR on hospital admission in COVID-19 patients were included.
- Data on disease severity and mortality were analyzed, focusing on ROC analyses and AUC values.
Main Results:
- Higher PLR values were associated with more severe COVID-19 disease and increased mortality.
- ROC analysis showed inconsistent diagnostic utility for PLR, with AUC values varying for severity and mortality prediction.
- Heterogeneity in study populations may explain the observed inconsistencies in PLR's diagnostic performance.
Conclusions:
- PLR is indirectly linked to COVID-19 severity and mortality, reflecting underlying inflammatory and hematological changes.
- PLR may serve as a complementary marker for assessing COVID-19 patient prognosis.
- Further research is needed to fully elucidate the role of PLR in COVID-19-Associated Coagulopathy and patient outcomes.
Abstract:
Background: Patients with COVID-19 often develop COVID-19-Associated Coagulopathy (CAC)-an imbalance between procoagulant and anticoagulant pathways resulting from the uncontrolled inflammatory response triggered by SARS-CoV-2 infection. This study aims to investigate the impact of a hematological and inflammatory parameter-the platelet-to-lymphocyte ratio (PLR)-on the severity and mortality of COVID-19. Methods: We conducted a comprehensive search of the PubMed database and yielded 75 articles published in the period of 2020-2025, of which 20 studies that evaluated the prognostic value of PLR on hospital admission in COVID-19 patients were included. The review particularly focuses on ROC analyses and reported AUC values. Results: A total of 20 studies were analyzed, including 13 studies assessing disease severity and 14 studies evaluating mortality. Higher PLR values have been observed in patients with a more severe course of COVID-19 compared to those with milder disease, and in non-survivors compared to survivors. However, the literature shows inconsistency regarding the diagnostic utility of PLR based on ROC curve analysis. The reported AUC values ranged from 0.559 to 0.811 for disease severity differentiation and from 0.474 to 0.758 for mortality, which may be related to the heterogeneity of the study populations included in the analysis. Conclusions: PLR may not serve as a direct bridge between inflammation and coagulation in COVID-19-Associated Coagulopathy, but it is indirectly linked to disease severity and mortality, as it reflects changes in both platelet and lymphocyte counts. It is a complementary marker that may assist clinicians in assessing COVID-19 patients but still requires further investigation.
