Evaluation of the efficacy of convalescent plasma in moderate to severe COVID-19 during 2020-2021: a retrospective observational study

Convalescent plasma therapy (CPT) is one of the treatment modalities used for COVID-19. Initial smaller studies showed the usefulness of CPT in COVID-19, but larger studies showed that it is not effective. This is a retrospective observational study conducted between 1st June 2020 and 31st July 2021 at a tertiary hospital in Noida, India. Our analysis was done on 213 COVID-19 patients, comprising 170 cases who were given convalescent plasma and 43 controls who did not get CPT. Outcomes analyzed were improvement in PaO2:FiO2 ratio (PFR) by day 5 of CPT, 28-day mortality, and level of inflammatory markers. Mean PFR before plasma transfusion was comparable between CPT and control groups (142.11±73.99 vs. 151.11±88.87, p=0.56). There was no significant difference in mean PFR after 5 days of CPT between cases and the control group (187.02±102.34 vs. 160.29±83.39, p=0.206). 28-day mortality was 47.05% in the CPT group and 37.20% in the control group (p=0.246). Mortality among the subgroup of patients on invasive mechanical ventilation was 89.74% in cases and 80% in controls (p=0.518). No significant difference was found in levels of serum ferritin, interleukin-6, and C-reactive protein between the two groups. Convalescent plasma does not have a significant effect on day 5 PFR and 28-day mortality. Our study could not find any subgroup of patients who would benefit from CPT. This study reinforces that CPT does not benefit moderate to severe patients with COVID-19.