Chronic obstructive pulmonary disease (COPD), a heterogeneous clinical syndrome characterized by chronic respiratory symptoms due to abnormalities of the airways and alveoli.

This chronic airway disease is associated with progressive airway obstruction, which arise from conditions such as bronchitis and bronchiolitis, as well as alveolar damage associated with emphysema. [1] COPD patients commonly present with persistent respiratory symptoms, including dyspnea, cough, sputum production, and episodes of acute exacerbation. [2]

More than 200 million people suffer from COPD, which is ranked as the 3rd most common cause of death globally. COPD is now becoming the most prevalent disease that markedly diminishes the quality of life for those affected and also a significant cause of healthcare expenses since it frequently requires hospitalization. Globally, about 3 million deaths occur due to COPD every year. [3,4] Pulmonary hypertension (PH), characterized by chronic elevation of pulmonary arterial pressure and pulmonary vascular resistance leading to right heart failure, is a major complication of COPD and is an established independent prognostic factor. PH due to COPD is classified as group 3, which comprises PH caused by lung diseases [5,6].

In COPD patients, airflow limitation cause alterations in pulmonary vasculature by intimal hyperplasia and smooth muscle hypertrophy/hyperplasia. Airway remodeling causes increased shear stress in the pulmonary arteries. When combined with vascular injury, this can induce neointimal lesions. Additionally, products from tobacco smoke may directly cause dysfunction in endothelial cells, resulting in impaired release of endothelial nitric oxide synthase (eNOS) and increased expression of vascular endothelial growth factor. These processes can contribute to the development of PH in patients with COPD. [7]

There are many causes of COPD, among them, smoking is the most common cause. It increases the intracellular Ca+ levels that in turn enhances the response of smooth muscles present in the airways to muscuarnic agonist and it also increase the oxidative stress, that further lead to inflammation of airways and finally culminate to progressive narrowing of airways and hyperinflation of lungs. [8,9] In patients with COPD, there ae vasculature abnormalities, that occur due to damage to microvasculature that supply’s the muscles of airways by narrowing of vessels due to deposition of extra cellar matrix proteins and proliferation of smooth muscle cells in response to alveolar injury that may further deteriorate COPD. [10]

Inflammation plays a significant role in pathophysiology of COPD. However, there is limited amount of data available in regards to inflammatory biomarkers in COPD. Recently, Neutrophil-Lymphocyte Ratio (NLR) and platelet to lymphocyte ratio (PLR) have been proposed as a novel marker of inflammation and plays a pivotal role in pathogenesis of COPD, because the levels of neutrophils, lymphocytes and platelets altered during the inflammatory phase of COPD. In inflammatory conditions, a complex web of interactions between immune-related cells, including lymphocytes and neutrophils, are involved in inflammation, which can cause irreversible damage and loss of respiratory tissue. [11] According to reports, the NLR and PLR can accurately represent chronic inflammatory conditions. They have been studied in a variety of disease states, including systemic lupus erythematosus, coronary artery disease, retinal artery occlusion, chronic kidney disease, and stable COPD. [12,13]

In addition, severe coronavirus disease 2019 (COVID-19) is associated with a sustained and amplified inflammatory response altering the leukocyte count, which is characterized by neutrophilia, lymphopenia, and thrombocytopenia. [14] Inflammation is caused by infectious diseases, and growing evidence supports its significant role in the progression of various viral pneumonia, including COVID-19. Severe inflammatory responses contribute to weak adaptive immune response, thereby resulting in immune response imbalance. Therefore, circulating biomarkers that can represent inflammation and immune status are potential predictors for the prognosis of COVID-19 patients. [15]

Several markers have been proposed to identify the progression towards severe stage of COVID, including C-reactive protein (CRP), D-dimer, lactate dehydrogenase (LDH), troponin I. [16] Leucocyte alterations involve both the lymphocyte and the neutrophil populations. Neutrophils, in fact, possess several inflammatory and pro-thrombotic properties such as the production of neutrophil extracellular traps (NETs) and reactive oxygen species (ROS), which can lead to sustained inflammation during SARS-CoV-2 infection. Lymphocytes, on the other hand, mainly exhibit the hallmarks of immune exhaustion with CD4 and CD8 T-cell loss, which has been linked to an amplified inflammatory response due to the persistent viral load and the consequent neutrophil stimulation. [17,18] Therefore, the present study is aimed to assess the Neutrophil-Lymphocyte Ratio (NLR), platelet to lymphocyte ratio (PLR) as markers of inflammation in COPD patients and post COVID/ COVID like syndrome patients with COPD.

A prospective study was conducted in in Department of General Medicine, Akash Institute of Medical Sciences and Research Centre (AIMSRC), Bengaluru, Karnataka, India. The study has been approved by the Institutional Ethics Committee and informed consent was obtained from all the study participants. Simple random sampling method was followed for recruiting the study subjects. Sample size was calculated by using the formula: Z21-a/2(S.D)2/d2. The obtained sample size for each group is 85. A total of 170 subjects were included in this study. They were divided into 2 groups. 85 COPD patients as group A and 85 Post COVID/COVID like syndrome with COPD patients as group B. Inclusion Criteria Subjects willing to participate in the study, individuals of both sexes aged > 40 years, patients with diagnosis of COPD based on spirometry post-bronchodilator forced expiratory volume in one second/forced expiratory volume (FEV1/FVC) ratio less than 0.7 as per Global Initiative for chronic Obstructive Lung Disease (GOLD) guidelines. Post COVID /COVID like syndrome patients with COPD whose diagnosis is established on previous RT-PCR positive test based on SRF ID or clinical findings of COVID. Exclusion Criteria Subjects not willing to participate in the study, patients with age of > 40 years, patients with pulmonary hypertension due to conditions other than COVID and post COVID /COVID like syndrome, patients without a diagnosis of COPD, patients with diagnosis of tuberculosis. Method of data and sample collection After taking informed and written consent, consecutive patients aged above 40 years, either with clinical findings of COPD or Post COVID/ COVID like syndrome or with confirmed diagnosis of COPD or Post COVID/COVID like syndrome with COPD were selected from General Medicine and Respiratory Medicine Departments. All the study subjects are evaluated clinically for incidence of Pulmonary Arterial Hypertension and are then subjected to investigations which include CBC. ECG, chest X - ray, pulmonary function test, HRCT Chest, D- Dimer (when indicated), 2D ECHO (when indicated) for confirmation of diagnosis. The patients are then diagnosed as COPD based on FEV1, values by Pulmonary Function test and classified based on Gold's criteria. The patients are further diagnosed with Pulmonary arterial hypertension and classified using 2D ECHO and the modified Bernoulli equation and Chmela formula. Sample collection Five ml fasting blood samples were collected from all the study participants, transferred 2 ml into EDTA tube and 3 ml in plain tube. The samples were centrifuged at 3000rpm for five minutes to obtain plasma/serum. Obtained plasma/serum sample was used for estimation of glucose (GOD-POD), urea (urease), creatinine (Jaffes), D-dimer (Immunoassay) were estimated by using biochemistry fully auto analyzer. EDTA samples were used for HbA1c and CBC analysis by using hematology analyzer. NLR, PLR MLR were calculated from the CBC values by using the formula. NLR: Neutrophil to lymphocyte ratio PLR: Platelet to lymphocyte ratio. Statistical analysis The results were expressed in form of frequency and percentage, Mean±SD. Continuous data student t test was used for statistical mean difference between the two groups or variables. P value <0.05 was considered as statistical significance. Data was analysed by using SPSS 22.0.

In the present study, in group A mean age was 48.47±6.3 years, fasting blood glucose 201.1±62.6 mg/dl, HbA1c 9.8±2.3 %, serum urea 34.39±15.9 mg/dl, serum creatinine 1.1±0.3 ng/dl and d-dimer 0.81±0.02 m/L. Only D-dimer showed significantly increased in group B compared to group A as shown in table 1. Among the hematological parameters, Hb 11.2±2.3 %, Red blood cell 4.14±0.67, Packed cell volume 31.9±5.2, White blood count 7966.48±1813, Platelets 2.7±0.77, Neutrophils 67.6±12.4, Lymphocytes 25.6±11.6 and Monocytes 5.9±3.1. Neutrophils were significantly increased whereas lymphocytes significant decrease in group B than group A. Concerned with inflammatory markers, NLR 7.5±1.9 and PLR 0.35±0.01 were significantly increased in group B compared with group A as shown in table 1. 

Table 1. Comparison of demographic, biochemical, hematological and inflammatory markers between group A and group B.

* p value<0.05 is considered as statistically significant.

COPD, is now becoming the most prevalent respiratory disease. COPD is a debilitating condition marked by persistent airflow limitation and inflammation that is not easily reversible. The NLR and PLR has gained attention as a systemic inflammatory marker due to its quick, accessible, and cost-effective measurement through routine blood investigations. In recent years, NLR and PLR has been explored as both a diagnostic and prognostic tool in the management of COPD. [19] Neutrophils are associated with inflammation, whereas lymphocytes indicate immunoregulation. These can indicate the systemic inflammation and also innate and adaptive immune-responses. Inflammation may cause changes in peripheral blood cell levels. More specifically, peripheral blood leukocytes include neutrophils, lymphocytes, monocytes and others. Each type of which holds a unique biological function in systemic inflammation. [20] In addition, platelets participate in thrombosis. Many studies have reported that platelets play a significant role in immuno-inflammatory response. Specifically, platelets can release a variety of immune-regulating cytokines, chemokines, and other mediators, thus regulating the inflammatory response in blood vessels in an autocrine or paracrine manner. Meanwhile, platelets could also regulate neutrophils, endothelial cells, and lymph directly, allowing them to recruit toward injured tissue. Therefore, because of this regulatory function of platelets, elevated PLR might indicate the relative active inflammatory response. [21,22] This study findings are consistent with studies conducted by others. In a study conducted by yang AP et al., reported that Elevated NLR and age were significantly associated with illness severity. The binary logistic analysis identified elevated NLR (hazard risk 2.46, 95% confidence interval [CI] 1.98-4.57) and age (HR 2.52, 95% CI 1.65–4.83) as independent factors for poor clinical outcome of COVID-19. NLR exhibited the largest area under the curve at 0.841, with the highest specificity (63.6%) and sensitivity (88%). They concluded that, elevated age and NLR can be considered as independent biomarkers for indicating poor clinical outcomes. [23] In a study conducted by Asperges E, et al., reported that NLR and PLR were higher in severe coronavirus disease 2019 (COVID-19). Both ratios were able to distinguish the outcomes at each timepoint. For NLR, the areas under the receiver operating characteristic curve (ROC) ranged between 0.59 and 0.81, and for PLR between 0.53 and 0.67. From each ROC curve we computed an optimal cutoff value. They concluded that NLR and PLR cutoffs are able to distinguish severity grades and mortality at different timepoints during the course of disease. [24] Sathyashree et al., reported that total leukocyte count, NLR, and PLR were significantly higher in non-survivors. They concluded that elevated leukocyte count, NLR, and PLR are associated with poor prognosis in COVID-19 patients. [25] In a study by George et al., reported significantly elevated NLR, d-NLR, PLR and RDW in severe group when compared to less severe group. From the ROC curve, it was established that d-NLR, NLR and WBC count proved to be a fair distinguisher (area under the curve between 0.7- 0.8) in predicting the clinical severity in COVID-19 patients. NLR and WBC count was found to be having the highest sensitivity of 82%, while d-NLR proved to be highly specific. Elevated age was also significantly associated with illness severity. They concluded that elevated age, WBC count, NLR, d-NLR, RDW and PLR may be considered as useful prognostic biomarkers for predicting the severity of COVID-19 and adverse outcome, with NLR and WBC count showing the highest sensitivity and d-NLR with the highest specificity. [26] Wang Z et al., conducted a retrospective study and showed that NLR greater than 3 is significantly associated with COPD, with a P-value of 0.0001 and an odds ratio of 3.8. [27] The meta-analysis conducted by Wang Y, et al., which analysed 15 studies and involved 6783 participants, found that COPD is significantly associated with a higher NLR. [28]

The present study may conclude that, significantly increased levels of D-dimer, Neutrophils, NLR, PLR in group B whereas lymphocytes showed significant decrease in group B. Therefore, NLR and PLR may serve as markers of inflammation in post COVID/ COVID like syndrome patients with COPD. Further studies with large sample size are recommended.

Acknowledgements: We would like to thank the authorities of Akash Institute of Medical Sciences and Research Centre (AIMSRC), Bengaluru, Karnataka, India.

Conflict of interest: Nil

Funding: Nil