4 DISCUSSION
In this study, the comparison of CSD and cancer examined as comorbidities in patients with COVID-19 was investigated for the first time in the literature to the best of our knowledge. It was observed that patients with CSD and/or cancer were at higher risk in terms of intensive care admission, intubation, rate of complications and survival compared to patients without comorbidities. In addition, there was no significant difference in clinical parameters and survival between those with cancer and those with CSD, except that Hb and ferritin levels were significantly different in those with cancer.
In a large COVID-19 clinical study conducted in China, the mean age of participants was 47 years, and 58% of the participants were male.8 However, in our study, the mean age was lower, and the proportion of males was almost similar. The absence of patients under the age of 18 years may be the main reason for the mean age difference in our participants. In addition, the mean age of patients with CSD and cancer was higher than that of patients without comorbidities. This situation can be explained by the higher prevalence of CSD in older patients.9 The most common symptoms in the patients in our study were cough, fever and myalgia, which was similar to the results reported in the literature.10In a meta-analysis examining the prevalence of comorbidities, the most frequently reported ones were hypertension and diabetes.11 Similarly, the most common CSDs in the patients in our study were diseases related to the cardiovascular and endocrinological systems. Evaluation of hypertension under the title of cardiovascular system diseases and diabetes under the title of endocrinological system diseases could have had an effect on this result.
CRP is an acute phase reactant induced by interleukin (IL)-6 produced by the liver and is a sensitive biomarker in various inflammatory conditions such as infection and tissue damage.12 An increase in serum CRP levels has been observed in many studies as a reliable indicator of the presence and severity of SARS-CoV-2 infection.13,14 Damage to any of the multiple cell types containing LDH results in increased serum LDH levels. Therefore, elevated LDH is common in critically ill patients with COVID-19 and is believed to indicate poor prognosis.12 D-dimer is another important biomarker investigated as a potential prognostic factor of disease severity in COVID-19. It was found that compared to patients with D-dimer levels of <2.0 μg/mL, those with higher D-dimer levels had a higher incidence of comorbidities such as diabetes, hypertension, coronary artery disease and stroke.15 In our study, CRP, LDH and D-dimer levels were significantly higher in and patients with CSD and cancer compared to those without comorbidities.
NLR has been used as a prognostic indicator for conditions such as acute-on-chronic hepatitis B liver failure16 and as a mortality risk factor for malignancy, acute coronary syndrome and cerebral haemorrhage.17,18,19 Recent studies suggest that NLR is an early predictor of critical illness in SARS-CoV-2 infection.20 It is reported that patients with severe COVID-19 have higher neutrophil count and lower lymphocyte count compared to nonsevere patients, and therefore, NLR tends to be higher in patients with severe infection.21 This explains why NLR was significantly higher in patients with cancer and CSD along with COVID-19 compared to patients with COVID-19 without comorbidities in our study.
Patients with CSD who are also infected with SARS-CoV-2 require more medical attention, such as intensive care admission and mechanical ventilation therapy.22 Similarly, patients with cancer have a higher incidence of intensive care admission, mechanical ventilation and complications.23,24 In our study, the rate of referral to the intensive care unit exceeded 20% in patients with cancer and CSD, whereas this rate was 5% in patients without comorbidities. Whereas 25% of the patients admitted to the intensive care unit without comorbidities required intubation, this rate exceeded 50% in those with CSD and cancer. Similar to the literature, in our study, intensive care admission and need for mechanical ventilation in patients with CSD and cancer were clinically significantly higher. However, there was no significant difference between patients with CSD and those with cancer. It is observed that the benignity or malignancy of the comorbid chronic processes does not have a significant effect on the COVID-19 clinical picture; this information is contributed to the literature for the first time in this study.
The survival rates of those with CSD and cancer were significantly lower than those without comorbidities. It was not surprising that the mortality rates were high (33.3%) in the group with both cancer and CSD (Group 4). Similar to the results reported in many studies, the presence of CSD and cancer was associated with mortality in our study.25,26
In a meta-analysis, it was demonstrated that patients with severe COVID-19 had lower Hb levels than those with moderately severe COVID-19. This suggests that the severity and prognosis of the disease in patients with COVID-19 may be associated with lower Hb levels.27 Patients with anaemia have a higher prevalence of comorbidities such as hypertension, cardiovascular disease or chronic kidney disease, all of which are known risk factors for COVID-19-related death.2 Ferritin not only has a role in iron storage, but also is a well-known acute phase reactant.28 Ferritin H chain may be important in activating macrophages to increase the secretion of inflammatory cytokines observed in patients with COVID-19. The clinical picture in critical patients with COVID-19 resembles that of those with macrophage activating syndrome, which is often associated with high levels of ferritin and cytokine storms.29 In our study, unlike other parameters, there was a clinically significant difference only in high ferritin and low Hb levels between patients with CSD and those with cancer. Patients with cancer were significantly different from patients of other groups in this regard. One of the most important factors for this difference may be that the release of inflammatory cytokines is higher in patients with cancer than in those with other CSDs. In addition, the grouping of haematological cancers under the title of cancer and higher frequency of anaemia in these patients may be another factor.
This study has some limitations. The number of samples was not homogeneously distributed among the groups. As the study was retrospective, the severity of comorbidities and compliance of patients with medical prescriptions could not be evaluated. It is known that some metabolic variables can reach pathological values in COVID-19 as well as some chronic inflammatory processes. Since there are no subjects without COVID-19 among our participants, it cannot be demonstrated to what extent COVID-19 affects the current values of these measurements.