The ongoing pandemic of COVID-19 has imposed an enormous burden on the societies and individuals across the world[13–15]. Early studies have categorized the clinical spectrum of COVID-19 into mild, moderate, severe, or critical illness. More than 80% of patients tend to recover with supportive care. Fewer than 20% of patients require hospital admission for advanced healthcare. Previous studies have identified several risk factors for severe or critical illness; these include age, presence of comorbidities (such as hypertension, obesity, and diabetes), and certain laboratory indices[6, 8, 16–18]. However, young patients with no comorbid conditions who initially exhibit mild illness may rapidly develop severe or critical illness, and may even die. Therefore, it is important to identify patients who have mild symptom at onset, but who are at a high-risk of developing critical illness. This can help optimize the use of healthcare resources and facilitate early intervention for high-risk patients.
COVID-19 may affect multiple organ systems in the body; however, it most commonly causes pneumonia. Respiratory involvement is also the most common cause of death of patients with COVID-19. Therefore, we first investigated the chest imaging findings in COVID-19 with mild clinical symptoms. Our results indicate that a sizable proportion of patients (68.0%) with mild clinical symptoms may have abnormal chest imaging findings. Ground-glass opacity was the most common chest imaging abnormality. We further compared the differences between patients with improved or deteriorated outcomes during the stay at the mobile cabin hospital. Patients with deteriorated outcomes were significantly more likely to exhibit abnormal chest imaging findings than patients who had improved outcomes. Very few patients in our cohort had cough (2 patients) or shortness of breath (2 patients), even though a majority of patients (85, 68.0%) had abnormal chest imaging findings. This is consistent with a previous report that documented typical abnormal chest imaging findings in asymptomatic patients with COVID-19. Therefore, we recommend chest imaging study of all patients with COVID-19, including those with mild symptoms. This may help identify patients who are at high risk of developing severe illness.
Chest imaging helps in the direct evaluation of pulmonary involvement in patients with COVID-19. However, chest imaging, especially CT scan, entails the risk of radiation exposure. It is also inconvenient to frequently perform repeat chest imaging. Peripheral oxygen saturation measurement is another method to indirectly assess the pulmonary ventilation and oxygenation status. Moreover, it is a convenient and safe procedure. In our study, patients with deteriorated outcomes were significantly more likely to have low peripheral oxygen saturation than patients with improved outcomes. This suggested that monitoring of peripheral oxygen saturation is a useful method for identification of patients who may develop severe illness. Early initiation of oxygen therapy may reverse or save their lives.
In our study, patients with deteriorated outcomes were more likely to have moderately elevated temperature and elevated blood leukocyte count. Fever is the most common presenting feature of COVID-19. Studies have shown that SARS-CoV may attack leukocytes resulting in reduced leukocyte counts[25, 26]. Further studies are required to assess the predictive value of body temperature and leukocyte count in COVID-19 patients with mild symptoms.
Several studies have identified comorbid conditions such as hypertension, diabetes, and chronic pulmonary disease as risk factors for severe and critical COVID-19 illness[6, 8, 16–18]. In our study, we did not observe any significant association of comorbidities with chest imaging findings or outcomes. Age was also found to be a risk factor for increased morbidity and mortality in COVID-19 patients. In our study, older patients were more likely to have abnormal chest CT findings. However, age was not associated with the short-term outcome. We believe that the risk factors may differ depending on the initial presentation (mild or severe symptoms) of COVID-19 patients.
COVID-19 may impair the functioning of multiple organs and systems in the body. In addition to lung injury, liver and kidney are also frequently affected in these patients. Some of the patients in our cohort exhibited mild elevation in liver enzyme levels; however, there was no significant difference between patients with deteriorated or improved outcomes in this respect. None of our patients showed any sign of kidney injury.
The single-center scope of our study and the relatively small sample size are some of the limitations of our study. We were only able to study adult male patients, since our mobile cabin hospital was exclusively dedicated for hospitalization of adult male COVID-19 patients. Lastly, this was an observational study; therefore, we could not control the treatment modalities, such as oxygen supplementation or administration of certain traditional Chinese medicines.
In summary, we observed an association of chest imaging findings, peripheral blood oxygen saturation, and body temperature with disease deterioration in adult male COVID-19 patients with mild clinical symptoms. Close monitoring of these indices may facilitate identification of patients who are high risk of developing severe or critical illness. This can help optimize the use of healthcare resources and facilitate early interventions to reduce morbidity and mortality in high-risk patients.