Serial Changes of Long COVID Symptoms and Clinical Utility of Serum Antibody Titers for Evaluation of Long COVID

Background: Various symptoms persist even after the acute symptoms in about one third of patients with COVID-19. In February 2021, we established an outpatient clinic in a university hospital for patients with long COVID and started medical treatment for sequelae that persisted one month or more after infection. Methods: To determine the key factors that affect the onset and clinical course of sequelae, a retrospective analysis was performed at Okayama University Hospital (Japan) between February and July 2021. We focused on changes in the numbers of symptoms and the background of the patients during a three-month period from the first outpatient visit. We also examined the relationship with SARS-CoV-2 antibody titers. Results: Information was obtained from medical records for 65 patients. The symptoms of sequelae were diverse, with more than 20 types. The most frequent symptoms were general malaise, dysosmia, dysgeusia, sleeplessness, and headache. These symptoms improved in about 60% of the patients after 3 months. Patients who required hospitalization and had a poor condition in the acute phase and patients who received oxygen/dexamethasone therapy had higher antibody titers at the time of consultation. Patients with antibody titers ≥200 U/mL showed significantly fewer improvements in long COVID symptoms in 1 month, but they showed improvements at 3 months after the first visit. Conclusion: Long COVID symptoms were improved at 3 months after the initial visit in more than half of the patients. Serum antibody titers were higher in patients who experienced a severe acute phase, but the serum antibody titers did not seem to be directly related to the long-term persistence of long COVID symptoms.