Introduction
After appearing in Wuhan, China in December 2019, coronavirus disease (COVID-19) spread rapidly around the world, with over 3 million confirmed cases by the end of April 2020. In the majority of infected patients, COVID-19 is either asymptomatic or presents with mild symptoms such as loss of taste and smell, sore throat, fatigue, and joint pain. However, it can have a much more severe course in older people, patients with hypertension (HT), and conditions that can impair immunity such as diabetes mellitus (DM), HIV, long-term immunosuppressive therapy, and pregnancy 1.
While many comorbidities have been associated with COVID-19 mortality, there are also laboratory diagnostic tests associated with early poor prognosis. Of these, the most frequently used parameters are D-dimer, ferritin, leukopenia, fibrinogen, prothrombin time, and IL-6 level. These parameters alone are not effective in directing treatment, but evaluation of correlation with clinical condition revealed a relationship with macrophage activation syndrome (MAS), which is among the most important causes of mortality. This led to the investigation of parameters that can be associated with mortality in this emerging disease 2,3.
Carbon monoxide (CO) is naturally synthesized in the body and plays an important role in the regulation of physiological functions such as vasodilation, angiogenesis, vascular remodeling, protection against tissue damage, and modulation of the inflammatory response. Approximately 85% of CO is produced by heme oxygenase and is excreted from the body through the respiratory system 4,5. In critical diseases such as acute respiratory failure, chronic obstructive pulmonary disease, acute pulmonary embolism, and acute myocardial infarction, low initial endogenous carboxyhemoglobin (COHb) level has been associated with high mortality and poor prognosis . The leading causes of morbidity and mortality in COVID-19 are acute respiratory failure, microthombi, and cardiac involvement 5-8.
COVID-19 is a new disease that does not have specific laboratory findings as in other known diseases, and as such is the focus of intense research. The aim of the present study was to determine the value of COHb levels measured at admission and follow-up in the prediction of clinical course and prognosis in COVID-19 patients who develop MAS and acute respiratory failure.