C-reactive protein and lactate dehydrogenase are useful biomarkers for predicting the requirement for oxygen therapy in outpatients with coronavirus disease 2019

ABSTRACT

BackgroundIt is critical for clinicians seeing outpatients with coronavirus disease 2019 (COVID-19) to identify those who will require oxygen therapy after the hospital visit. Although studies on biomarkers predicting mortality or ventilator requirement in hospitalized patients with COVID-19 have been conducted, research on biomarkers predicting the need for oxygen therapy in outpatients is sparse. MethodsPatients with COVID-19 who visited Asahikawa City Hospital on an outpatient basis were included in the study. In total, 287 new outpatients visited between April 2021 and September 2021, and 142 underwent blood testing. All blood tests were performed before any treatments for COVID-19 were started. Demographic information, laboratory data, and clinical treatment information were extracted from the electronic medical records. Risk factors associated with oxygen therapy were explored. ResultsIn total, 40 of 142 patients who underwent blood testing required oxygen therapy within 7 days after blood samples were taken, and all other patients recovered without oxygen therapy. C-reactive protein (CRP) and lactate dehydrogenase (LDH) levels were significantly higher in patients who required oxygen therapy, and their cutoffs were 36 mg/L (sensitivity, 0.802; specificity, 0.725) and 267 U/L (sensitivity, 0.713; specificity, 0.750), respectively. Multivariate logistic regression identified age, body mass index, CRP [≥] 36 mg/L, and LDH [≥] 267 U/L as significant risk factors for oxygen therapy requirement. This study suggests that elevated CRP and LDH levels are independent risk factors for oxygen therapy in outpatients with COVID-19. Further confirmatory studies are needed.