Convalescent plasma therapy in patients with severe COVID-19, A single-arm, retrospective study

Convalescent plasma (CP) therapy has been suggested as a treatment for emerging viral diseases. Moreover, many studies have been conducted to evaluate the efficacy of COVID-19 CP therapy, with some of them indicating that CP may be a promising treatment for the disease. However, the evidence for CP therapy's effectiveness in severe COVID-19 cases is limited. So, this study aimed to assess the probable effects of CP therapy in patients diagnosed with severe COVID-19. The study was designed as a single-arm, retrospective cohort of patients with severe COVID. Demographic data, laboratory test reports, and convalescent plasma transfusion doses were collected from medical records for patients before and after convalescent plasma transfusion. The clinical outcomes were hospital discharge and death. Also, laboratory parameters considered secondary outcomes. After CP therapy, some symptoms improved, especially in patients under 55 years old, as follows. Respiratory function was significantly enhanced after convalescent plasma transfusion, and the inflammatory biomarkers' values decreased significantly (p < 0.05). Moreover, the estimated median of partial thromboplastin time (PTT) and Prothrombin time (PT) in patients did not change after CP therapy (p > 0.05). Regarding COVID-19 mortality, a strong association was found between older ages and death (p < 0.001). Also, CP transfusion in the early days of admission was effective in treatment outcomes (p = 0.023). Other characteristics, including sex, blood group, number of CP transfusions, and preexisting conditions, did not significantly correlate with mortality. In conclusion, this study demonstrates the effectiveness of CP therapy in patients under the age of 55. Despite some improvement, we could not say that they were entirely due to the CP treatment. More extensive randomized clinical trials that cover different stages of the disease are needed.