Lymphocyte as A Predictive Marker for Seronegativity of COVID-19

the month of December 2019, in Wuhan Province of China,
multiple cases of pneumonia with an unknown origin were reported...


Introduction
In the month of December 2019, in Wuhan Province of China, multiple cases of pneumonia with an unknown origin were reported.
By PCR and bronchoalveolar lavage studies, it was confirmed that the causative microorganism belongs to virus family and name coronavirus/Noval Covid-19 (SARS-COV-2) AND DISEASES NAMED AS covid-19 [1]. The virus got international attention as it spreads to Japan, Korea, Iran, India and New Zealand. America and Italy were badly affected by this virus, and the mortality rate went beyond 8%. In March WHO declared Covid as the pandemic of 20th century. Pakistan is badly hit by covid 19, and in the first week of June the total number of confirmed cases was above 150 thousand and deaths were around 3000. While the world census is above 8 million total confirmed cases with 0.5million deaths.
Lymphocytes play a pivotal role in maintaining our immune system.
The alteration in the total lymphocyte count after viral infection indicates a potential association between lymphocyte and viral pathogenic mechanism [2,3]. The studies Conducted after COVID 19 declared as a pandemic, indicated showed a low lymphocyte count, but its impact on seronegativity of COVID is still unknown [4]. I this article we aimed to establish a role of lymphocyte count and number of days taken for seroconversion of COVID 19.

Patients and Methods
It is a longitudinal study in which a total of 142 patients have been monitored for 7 to 35 days admitted in a field hospital in the 20 th of April to the 30 th of May. All patients were male, and age ranges from 20 to 84 years. All patients were confirmed covid case diagnosed on nasopharyngeal sample PCR. The patients were further classified into two groups, those who stayed less than 8 days and those who stayed more than 8 days. Patient's lymphocyte counts were monitored at the time of admission, and their outcome is monitored.

Results
142 patients of COVID-19 included in this study. The median age was years, and all were male. Most of the patients were asymptomatic or had mild symptoms of Covid. Three of the patients died during the treatment. Their stay in the hospital while the rest of 139 was fully recovered. 07 of them were shifted to ICU based on symptoms and chest X-ray findings. It is seen that patients with low lymphocyte count have taken more than 2 weeks to have their PCR negative, while those with normal or high lymphocyte count have cleared the virus in a time span of a week (Tables 1 & 2). The mean age of patients was 37 years, while the average stays of patients 11 days with SD deviation _5.6. In addition, the mean lymphocytic count of 142 patients was 25% with SD 12.5, while the absolute lymphocytic count was 1.80 with SD 1.3. We analyze the level of lymphocytes and relate it with the number of days patients spent in a field hospital and days they have taken for seroconversion. 61 out of 142 patients have stayed more than 8 days, and their PCR was negative after more than 14 days. All of them have low lymphocyte count at the time of admission. *Correlation is significant at the 0.05 level (2-tailed).

Discussion
Lymphocytes play an important role in our body defense system.
Lymphocyte count is an index of disease progression and severity.
Differential lymphocyte count is often employed to diagnose certain diseases [5,6]. Acute disease conditions are associated with raised macrophages and neutrophil count. In contrast, chronicity is associated with the prevalence of lymphocyte numbers. A rise in eosinophil count is frequently associated with underlying parasitic and allergic aetiology [7,8]. Similarly, infection with Severe Acute Respiratory Syndrome Virus-2 (SARS-CoV-2) is associated with a change in leukocyte count [9]. A general trend seen in most of the COVID patients is the raise in lymphocyte count [10]. Looking at the usual trend of disease severity, most of the patients develop a milder form of the disease with benign signs and symptoms. Many of the diagnosed patients tested with Rt-PCR were asymptomatic. This is attributed to natural immunity of the host to SARS-CoV-2 [11].

Conclusion
The finding of studies showed a clear association between lymphocyte count and seroconversion, as those patients with low lymphocyte count have a longer duration of stay and adverse outcomes, and 7 of them shifted to ICU and 3 of them died. There are a few other factors that contributed to ICU and deaths, but lymphocyte is the only marker that determines seroconversion.