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"The right test, on the right specimen, collected at the right time, is essential for reliable diagnosis" Dr Prashant Goyal

Clinical significance of NLR, PLR & LMR in COVID-19

The clinical presentation of COVID-19, varies from no symptoms to severe symptoms with complications like acute respiratory failure, acute respiratory distress syndrome, metabolic acidosis, coagulopathy, and septic shock.

A full blood count is a routine, inexpensive and easy test that provides information about formed blood contents. Patients with severe COVID-19 disease present with increased leucocytosis, neutrophilia, lymphopenia, eosinopenia and thrombocytopenia than those with non-severe disease.

Recently, reports on the feasibility of few new haematological parameters like, Neutrophil to Lymphocyte ratio (NLR), Lymphocyte to Monocyte ratio (LMR) and Platelet to Lymphocyte ratio (PLR) in predicting prognosis in patients with SARS-CoV-2 infection have been published. The current study shows that these parameters may be a rapid, cost-effective, widely available, useful prognostic factor in the early screening of critical illness in patients with confirmed COVID-19. These parameters are more sensitive than individual levels of neutrophils, lymphocytes and platelets count. Although further studies with a larger sample size will be needed to properly assess the significance of these parameters in COVID-19.

NLR is an indicator of subclinical systemic inflammation, as neutrophils and lymphocytes play a significant role in inflammation and tumour immunology. NLR may be related to the severity of the infection and also indicates the outcome of the condition. Elevated NLR is found to be an independent prognostic biomarker for COVID-19 patients.

LMR has also been considered as a marker of inflammation including Tuberculosis and various cancers. Low LMR is considered to be a poor prognostic indicator.

PLR is also a novel inflammatory marker. High PLR reflects inflammation, atherosclerosis and platelet activation. Apart from being associated with various diseases, PLR is also an independent prognostic marker to differentiate severe versus non-severe disease in COVID-19 patients.

Early recognition of the severe cases allows for early triaging and timely initiation of management. While many acute phase reactants like C-reactive protein, lactate dehydrogenase, ferritin, and procalcitonin are frequently measured in COVID-19 patients; NLR, LMR and PLR can be easily accessible and are cost-effective especially for developing countries.


Dr Megha Gupta, MD

(Consultant Pathologist, Accuprobe Diagnostics)




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