Our primary aim in this study was to evaluate whether age, APACHE II value, presence of comorbidity, GCS, and baseline lymphocyte count were successful in predicting mortality in COVID 19 patients. Our study determined that the baseline lymphocyte value, APACHE II score, and the presence of any comorbidity are independent prognostic factors for mortality.
For many years, many scoring systems have been used in intensive care units to predict mortality and morbidity. Among these systems, APACHE II is accepted as the most successful scoring system in predicting mortality in all intensive care types and different patient groups (9, 10 ). In some articles, it has been reported to be successful in COVID 19 patients (11, 12). A study conducted by Zou et al., they stated that the APACHE II value of 17 or above in COVID 19 patients was an independent predictor for hospital mortality (13). Our study determined that the APACHE II value of > 19 and above is an independent risk factor, and death is 76 times more common in these cases. APACHE II scoring, which is calculated by taking the worst values during admission to intensive care, acts as an early warning system for physicians' high scores following these cases. These scoring systems are widely used in centers where intensive patient admissions are made during the pandemic, and they are instrumental in planning the treatment process of cases with high APACHE II values.
Although there is not enough information about using the Glasgow coma scale, which is frequently preferred in neurological examination in intensive care, in COVID − 19 cases, the GCS data can be based on studies using APACHE II since it is a parameter of APACHE II scoring. Our study showed that GCS being 10 or less has a significant relationship with mortality. In 28.7% of the cases, the GCS was 10 or less, and the mortality was 90.3%.
In the COVID 19 outbreak, it was observed that mortality rates were different in different age groups. It is observed that pulmonary physiology, pathology, and functions change in the presence of lung infection with aging. Therefore, in elderly individuals, response to the disease and tolerability deteriorate, and the mortality rate increases (14). Studies on advanced age COVID 19 patients have shown an increased risk of death (15–18). In our study, 56.5% of the cases were 65 years old and above, and the mortality rate in these cases was significantly higher compared to patients aged 65 years or younger.
The presence of concomitant diseases in COVID 19 cases complicates the clinical picture. In their study by Chen et al., in which they evaluated the epidemiological and clinical characteristics of the cases they followed up with COVID 19 viral infection, they determined the presence of chronic disease in 51% of the cases and stated that cardiovascular, cerebrovascular disease, and diabetes mellitus were the most common accompanying diseases. They indicate in their research that mortality is higher in cases with comorbidity (19). In our research, we observed that 82.4% of our cases had at least one concomitant disease. The most common accompanying disease was hypertension (42.6%), followed by diabetes mellitus (36.1%). In our study, unlike Chen et al., the accompanying cardiovascular disease rate was in the 3rd rank with 28.7%. While any comorbidity's presence increased the risk of death eight times, mortality was found to be statistically significantly higher in patients with diabetes mellitus compared to those without diabetes mellitus.
The absolute value of lymphocytes decreases in COVID 19 associated viral infection. The reason for this decrease is related to the effect of 2019-nCoV on SARS-CoV lymphocytes, especially T lymphocytes. Virus particles spread to the respiratory mucosa and initiate a cytokine storm in the body. This situation stimulates the immune system and causes changes in peripheral white blood cells and immune cells such as lymphocytes. Some patients progress rapidly and pass away by developing ARDS, septic shock, and multiple organ failure. For this reason, early detection and timely treatment of critical cases are vital. The decrease in the absolute lymphocyte count during admission to intensive care is a laboratory parameter that supports clinicians' diagnosis during the diagnosis of COVID 19. In comparison, Huang (20) and colleagues stated that their absolute lymphocyte count was < 1.0 × 10⁹ / L in 63% of their patients, Fan et al. showed that absolute lymphocyte count < 0.6 × 10⁹ / L had a significant correlation with mortality (7). In our study, when we evaluated the mortality relation of absolute lymphocyte count < 0.8 × 10⁹ / L, we determined that lymphocyte count < 0.8 × 10⁹ / L was an independent predictor for mortality. Absolute lymphocyte count < 0.8 × 10⁹ / L increased the risk of death seven times.
Frater et al. state that there is some geographic variation in the percentage of COVID-19 patients presenting with lymphopenia in their article evaluating COVID 19 and clinical, hematological laboratory findings (21). For example, an article from Singapore reporting several COVID-19 patients describes a much lower percentage of lymphopenia patients, as in a retrospective analysis of COVID-19 patients from Zhejiang Province, located ~ 450 miles from Wuhan (7, 22). In contrast, in studies reported from Italy, lymphopenia is common in most patients admitted to the emergency room (23). The reasons for these and similar discrepancies are unclear, although they are probably multifactorial. Due to viral genomic mutations, it is possible that the immunological response to the virus will change as the pandemic spreads to other countries. Another possibility is that testing patients is not uniform, and the degree of lymphopenia can vary depending on the time of admittance. In our study, we have observed that 74 of 108 patients had an absolute lymphocyte value < 0.8 × 10⁹ / L.
There were some limitations in our study. The first is that it is a retrospective study, and the second is that there is no long-term (28 days or 6 months) data when determining intensive care and hospital mortality. Besides, we think that further studies should be conducted that comparative studies of baseline absolute lymphocyte count with data from different countries may help determine the cut-off value for lymphopenia.