Note: The risk of bias by domain corresponds to the highest risk of bias among outcomes by domain.
The overall risk of bias corresponds to the overall highest risk of bias assessed among outcomes.
Bias | Author's judgement | Support for judgement |
Randomization |
Low |
Quote: "A web-system was used to provide simple randomisation (without stratification or minimisation) with allocation concealment until randomisation had been completed."
Allocation sequence random. Allocation sequence concealed. Imbalances in baseline characteristics appear to be compatible with chance. |
Deviations from intervention |
Low |
Quote: "Participants and local study staff were not masked to the allocated treatment."
Comment: Unblinded study (participants and personnel/carers). Deviations from intended intervention arising because of the study context: Administration of co-interventions of interest, antivirals, biologics and corticosteroids, reported and balanced between groups. 494/5795 (9%) assigned to convalescent plasma did not receive treatment and 17/5763 (<1%) participants assigned to control received convalescent plasma. Overall, the deviation was too small to affect the outcome. Data for the outcome were analyzed using intention-to-treat analysis. This method was considered appropriate to estimate the effect of assignment to intervention. Risk assessed to be low for the outcomes: Mortality (D28). Clinical improvement (D28). |
Missing outcome data |
Low |
Comment: 11588 participants randomized; 11588 participants analyzed.
Data available for all or nearly all participants randomized. Risk assessed to be low for the outcomes: Mortality (D28). Clinical improvement (D28) |
Measurement of the outcome |
Some concerns |
Comment: Method of measuring the outcome probably appropriate. Measurement or ascertainment of outcome probably does not differ between groups. Unblinded study (outcome assessor) MORTALITY Mortality is an observer-reported outcomes not involving judgement. Risk assessed to be low for the outcome: Mortality (D28). CLINICAL IMPROVEMENT Clinical improvement (defined as discharge from hospital) requires clinical judgement and could be affected by knowledge of intervention receipt. Risk assessed to be some concerns for the outcomes: Clinical improvement (D28). |
Selection of the reported results |
Low |
Comment: The protocol and statistical analysis plan (prospective, version 1.0.; dated 19th of March 2020) and registry (retrospective, dated 11th of May) were available.
Outcomes pre-specified. Results were not selected from multiple outcome measurements or analyses of the data. Trial analyzed as pre-specified. Risk assessed to be low for the outcomes: Mortality (D28). Clinical improvement (D28) |
Overall risk of bias |
Some concerns |