Abstract

Introduction: COVID-19 is a highly contagious and deadly disease. However, there is no accurate diagnostic test to predict its severity. The aim of this study was to determine the relationship between the lymphocyte counts and CRP levels and the severity of pulmonary involvement shown in the CT scan of the patients with pneumonia caused by COVID-19.

Methods: In this cross-sectional study, demographic information and laboratory findings of the patients with COVID-19 were collected. Then, each patient's pulmonary involvement was scored based on the CT scan results. The data were analyzed using SPSS 16 software as well as ANOVA, chi-square test, Pearson correlation coefficient, and ROC curve.

Results: Data of 125 COVID-19 patients with the mean age of 59.37 ± 1.5 showed that the prevalence of lymphocytes < 1100 × 10⁹/L and CRP > 100 mg/L was higher in the patients with severe pulmonary involvement than in those with mild involvement (p < 0.001). Furthermore, an increase in pulmonary involvement severity observed in HRCT led to decreased absolute blood lymphocyte count and increased CRP levels (p < 0.001). The CRP test with an area under the ROC curve of 0.76 could be an acceptable test for predicting the severity of pulmonary involvement in patients with pneumonia caused by COVID-19.

Conclusion: It was found out in this study that there was a significant positive correlation between CRP levels and the severity of COVID-19 pneumonia. The CRP test could also be an acceptable test for predicting the severity of pulmonary involvement in COVID-19.

Introduction

The outbreak of COVID-19 caused by the SARS-CoV-2 virus began in December 2019 in Wuhan, China, and on March 11, 2020, the World Health Organization declared it a pandemic and an emergency threatening public health1, 2. The most common clinical symptoms of the disease are fever and cough, along with other non-specific symptoms including dyspnea, headache, muscle aches, and fatigue3. The severity of the disease ranges from an asymptomatic condition to acute respiratory syndrome, organ failure, and even death in critical cases1, 2, 3, 4. Laboratory findings are also variable in this disease. Normal or low white blood cell counts, lymphopenia or thrombocytopenia, prolonged thromboplastin, and elevated C-reactive protein levels have been reported in COVID-19 patients5, 6.

Early detection of severe cases of COVID-19 is very important for all health care systems to predict the need for ICU beds and ventilators and to improve patient prognosis in the pandemic situation where medical resources face shortages4. Hence, researchers have always been seeking solutions for the early detection of severe cases. To this end, patients' clinical symptoms, laboratory findings, and imaging can be helpful. Various studies have used lymphocyte counts and CRP levels, as well as the severity of pulmonary involvement in CT scans, to diagnose and determine the severity of the disease3, 4, 5.

In some countries, such as China and Italy, the use of respiratory symptoms and fever along with lung CT scans, leukopenia or lymphopenia, and high CRP has been recommended for patient screening2. On the other hand, lung CT scans are used to diagnose and determine the severity of the disease in many international protocols3, 4, 5. Given that polymerase chain reaction testing (RT-PCR) may not be available in emergencies, and as lung CT scans are very expensive and can impose radiation and future complications for patients, the severity of pulmonary involvement due to COVID-19 might be determined through simpler and more accessible tests. Accordingly, the present study aimed to determine the relationship between lymphocyte counts and CRP levels and the severity of pulmonary involvement in CT scans of patients with pneumonia caused by COVID-19 in Imam Reza Hospital of Mashhad University Of Medical Sciences in 2020.

Methods

During the COVID-19 Epidemic in Iran, with randomized sampling, 165 COVID-19 patients entered the study based on clinical symptoms and positive PCR or CT scan findings at Imam Reza Hospital in Mashhad from March to May 2020, and a cross-sectional study was designed (This study was approved by the Ethics Committee of Mashhad University of Medical Sciences, with the code of ethics IR.MUMS.REC.1399.093). The inclusion criterion was a definitive diagnosis of COVID-19 based on clinical findings, plus PCR results, or positive lung CT scan findings on the first day of hospitalization. On the other hand, the exclusion criteria were defective information in patients' records, taking glucocorticoids or immunosuppressive drugs, undergoing chemotherapy, having an autoimmune disease, blood malignancies, osteomyelitis, and chronic infections. Figure 1).

Statistical analysis

The variables were described using central tendency (percentage and frequency, mean and standard deviation), and the data were analyzed (after assessing the normality condition for quantitative variables) through ANOVA and chi-square statistical tests. The Pearson correlation coefficient and the ROC curve were also used to determine the relationship between the two quantitative variables. The significance level in this study was considered less than 0.05.

Table 1.

Demographic information related to study participants

Group (The severity of lung involvement is based on HRCT) Mild (%) N Moderate (%) N Sever (%) N Very Sever (%) N Total (%) N P-value Sex Male (%) N (51/7) 15 (65/7) 23 (68/8) 22 (65/5) 19 (63/2) 79 0.526* Female (%) N (48/3) 14 (34/3) 12 (31/2) 10 (34/5) 10 (36/8) 46 Lymphopenia ( × 10⁹/L) > 1100 (%) N (31) 9 (51/4) 18 (78/1) 25 (69) 20 (57/6) 72 0.001 (69) 20 (48/6) 17 (21/9) 7 (31) 9 (42/4) 53 CRP (mg/L) > 100 (%) N (20/7) 6 (22/9) 8 953/1) 17 975/9) 22 (42/4) 53 0.001