The utility of serum amyloid A and other acute-phase reactants determination in ambulatory COVID-19 patients

Background: The unpredictable course of Coronavirus Disease 19 (COVID-19) is making good severity assessment tools crucial. This study aimed to assess the usefulness of serum amyloid A (SAA) and other acute-phase reactants (APRs) in ambulatory care COVID-19 patients and identified relationships between these markers and disease outcomes. Methods: From August to November 2020, patients seen in the outpatient department of the Clinic for Infectious and Tropical Diseases (Belgrade, Serbia) with confirmed COVID-19 were included. Patients were classified into mild, moderate, and severe disease groups based on World Health Organization criteria. SAA, C-reactive protein (CRP), interleukin-6 (IL-6), procalcitonin (PCT), ferritin, fibrinogen, D-dimer, albumin, and transferrin were measured. The median values of all APRs were compared between COVID-19 severity groups, hospitalized and non-hospitalized patients, and survivors and non-survivors. The Receiver operator characteristic (ROC) curve analysis was used for the classification characteristics assessment of individual APRs for the severity of illness, hospitalization, and survival. Results: Higher levels of SAA, CRP, IL-6, PCT, and lower levels of transferrin and albumin were observed in severe cases, hospitalized patients, and non-survivors. Based on ROC curve analysis AUC for SAA has fair classification performance for disease severity (0.794) and death (0.732) and good performance for hospitalization (0.853). Conclusion: SAA is a valuable marker in everyday practice for assessing COVID-19 severity and prognosis in ambulatory patients.