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: “We used a central web-based randomisation system with allocation concealment and no stratification to randomly assign participants (1:1) to receive convalescent plasma or placebo. Study researchers confirmed eligibility of participants and contacted an independent technician based at the central blood bank (Banc de Sang i Teixits de Catalunya, Barcelona, Spain), with no information about the participant, who used the web-based system to assign participants to the trial groups.”
Comment: Allocation sequence random. Allocation sequence concealed. Imbalances in baseline characteristics appear to be compatible with chance. |
| Deviations from intervention |
Low |
Quote: “Double-blind. An unmasked study nurse, who was not involved in patient follow-up, administered the investigational product. All participants and other investigators (including all personnel involved in patient follow-up, laboratory staff, and statisticians) were masked to treatment allocation.”
Comment: Blinded study (participants and personnel/carers) Our analysis for the binary outcome is an 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: Hospitalization or death. Mortality (D60 or more). Incidence of viral negative conversion (D7). WHO score 7 and above (D60 or more). Adverse events. Serious adverse events. |
| Missing outcome data |
Low |
Comment: 376 participants randomized; 376 participants analyzed.
Of note, 4 vs 3 participants did not receive allocated intervention and 2 vs 0 were lost to follow-up Data available for nearly all participants randomized. Risk assessed to be low for the outcomes: Hospitalization or death. Mortality (D60 or more). Incidence of viral negative conversion (D7). WHO score 7 and above (D60 or more). Adverse events. Serious adverse events. |
| Measurement of the outcome |
Low |
Comment: Method of measuring the outcome probably appropriate.
Measurement or ascertainment of outcome probably does not differ between groups. Blinded study (outcome assessor). Risk assessed to be low for the outcomes: Hospitalization or death. Mortality (D60 or more). Incidence of viral negative conversion. WHO score 7 and above (D60 or more). Adverse events. Serious adverse events. |
| Selection of the reported results |
Low |
Comment: The protocol, statistical analysis plan and registry (dated Nov 9, 2020) were available.
HOSPITALIZATION OR DEATH. MORTALITY. WHO SCORE 7 AND ABOVE. ADVERSE EVENTS. 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: Hospitalization or death. Mortality (D60 or more). WHO score 7 and above (D60 or more). Adverse events. VIRAL NEGATIVE CONVERSION. SERIOUS ADVERSE EVENTS. Outcome data acquired from direct contact with authors. Analysis performed by the COVID-NMA. Risk assessed to be low for the outcomes: Incidence of viral negative conversion (D7). Serious adverse events. |
| Overall risk of bias |
Low |