| Study |
Bias |
| Randomisation process |
Deviations from intended interventions |
Missing outcome data |
Measurement of the outcome |
Selection of the reported results |
Overall |
| Authors' judgement |
Support for judgement |
Authors' judgement |
Support for judgement |
Authors' judgement |
Support for judgement |
Authors' judgement |
Support for judgement |
Authors' judgement |
Support for judgement |
Authors' judgement |
Support for judgement |
| Subgroup 1.1.1 Individuals with moderate disease |
| Agarwal 2020 |
Low risk of bias |
The allocation sequence was random and concealed and there were no differences between intervention groups suggesting a problem with the randomization process. |
Some concerns |
Five participants in convalescent plasma arm and four in control arm did not receive the allocated intervention and this is probably a deviation from the intended intervention that arose because of the trial context. The analysis was appropriate. |
Low risk of bias |
Data for this outcome was available for 453 out of 464 participants. Data of six participants in the convalescent plasma arm and of five participants in the control arm were missing. |
Low risk of bias |
The measurement of the outcome was appropriate and it is unlikely that it differed between intervention groups. The data were collected in structured paper case record forms. |
Low risk of bias |
The data that produced this result was analysed in accordance with the predefined outcomes stated in the trial registration. |
Some concerns |
For the outcome "mortality" in this study, there is a low risk of bias from the randomization process, missing outcome data, measurement of the outcome and in selection of the reported result. However, there are some concerns for bias due to deviations from intended interventions. |
| AlQahtani 2020 |
Low risk of bias |
Participants were block randomized by computer‐generated random numbering in a 1:1 ratio to receive either convalescent plasma in addition to the standard therapy or standard of care alone and the allocation sequence was concealed. There are no baseline differences that would suggest a problem with randomisation. |
Low risk of bias |
Both participants and those delivering the intervention were aware of intervention received, but there were no deviations from intended interventions and the analysis was appropriate. |
Low risk of bias |
Data for this outcome was available for all 40 participants randomized. |
Low risk of bias |
The measurement of the outcome was appropriate and it is unlikely that it differed between intervention groups. The outcome assessors were aware of the intervention received, but it is unlikely that knowledge of intervention received could have affected outcome measurement. |
Some concerns |
The data that produced this result was not analysed in accordance with the predefined outcomes stated in the protocol, as the time point of the outcome measurement was not pre‐specified in the study protocol. |
Some concerns |
For the outcome "mortality", there are some concerns for bias in selection of reported results. However, for all the other domains, there is a low risk of bias. |
| Avendano‐Sola 2020 |
Low risk of bias |
Participants were randomized through a web‐based eCRF system (ORACLE clinical) in a 1:1 ratio to receive either convalescent plasma in addition to the standard therapy or standard of care alone and the allocation sequence was concealed. There are no baseline differences that would suggest a problem with randomisation. |
Low risk of bias |
Both participants and those delivering the intervention were aware of intervention received, but there were no deviations from intended interventions and the analysis was appropriate. |
Low risk of bias |
Data for this outcome was available for all 81 participants randomized. |
Low risk of bias |
The measurement of the outcome was appropriate and it is unlikely that it differed between intervention groups. The outcome assessors were aware of the intervention received, but it is unlikely that knowledge of intervention received could have affected outcome measurement. |
Low risk of bias |
The data that produced this result was analysed in accordance with the predefined outcomes stated in the trial registration. |
Low risk of bias |
For the outcome "mortality at up to day 28", there is a low risk of bias for all the domains. |
| Simonovich 2020 |
Low risk of bias |
Participants were randomized through a randomization program (REDCap) in a 2:1 ratio to receive either convalescent plasma or a placebo. The allocation sequence was random and concealed. There are no baseline differences that would suggest a problem with randomisation. |
Low risk of bias |
Both participants and carers and people delivering the intervention were unaware of the assigned intervention received and the analysis was appropriate. |
Low risk of bias |
From the 334 participants randomized data was available for 228 participants in the convalescent plasma group and 105 participants in the placebo group. The data of one participant in control group was missing, due to withdrawal of consent after randomisation and therefore the participant was excluded from the analysis. |
Low risk of bias |
Mortality is an objective outcome measure, appropriately measured and it is unlikely that the measurement differed between intervention groups. The outcome assessors were probably not aware of the intervention received. |
Low risk of bias |
The data that produced this result was analysed in accordance with the pre‐specified analysis plan and the outcome was reported as planned in the protocol. |
Low risk of bias |
For the outcome "mortality", all the domains have a low risk of bias. |
| Subgroup 1.1.2 Individuals with severe disease |
| Li 2020 |
Low risk of bias |
Participants were block randomized via computer‐generated random numbering in a 1:1 ratio to receive standard treatment coupled with convalescent plasma transfusion or standard treatment alone and the allocation sequence was concealed. There are no baseline differences that would suggest a problem with randomisation. |
Low risk of bias |
Both participants and those delivering the intervention were aware of intervention received, but there were no deviations from intended interventions and the analysis was appropriate. |
Low risk of bias |
Data for this outcome was available for nearly all participants randomized, a total of 101 out of 103 participants were included in the analysis. |
Low risk of bias |
The measurement of the outcome was appropriate and it is unlikely that it differed between intervention groups. The outcome assessors were not aware of the intervention received. |
Low risk of bias |
The data that produced this result was analysed in accordance with the pre‐specified analysis plan and the outcome was reported as planned in the protocol. |
Low risk of bias |
For the outcome "mortality at up to day 28", all the domains have a low risk of bias. |
| Subgroup 1.1.3 Individuals with moderate or severe disease |
| Horby 2021 |
Low risk of bias |
Participants were randomized through web‐based simple randomization with allocation concealment in a 1:1:1 ratio to a platform trial in a factorial design, receiving either convalescent plasma in addition to the standard therapy or standard of care alone. There are no baseline differences that would suggest a problem with randomisation. |
Low risk of bias |
Both participants and those delivering the intervention were aware of intervention received, but there were no deviations from intended interventions and the analysis was appropriate. |
Low risk of bias |
Data for this outcome was available for all 11,558 participants randomized. |
Low risk of bias |
The measurement of the outcome was appropriate and it is unlikely that it differed between intervention groups. The outcome assessors were probably not aware of the intervention received. |
Low risk of bias |
The data that produced this result was analysed in accordance with the pre‐specified analysis plan and the outcome was reported as planned in the protocol. |
Low risk of bias |
For the outcome "28‐day mortality", there was a low risk of bias for all the domains. |
| Ray 2020 |
Some concerns |
Participants were probably allocated randomly to either the standard of care group alone or standard of care with convalescent plasma group and there were no further information given on the randomization process. There is no information on the allocation concealment, the trial registry only indicates concealment through "Case Record Numbers". There were no baseline imbalances that would suggest a problem with randomisation. |
Low risk of bias |
Both participants and those delivering the intervention were aware of intervention received, but there were no deviations from intended interventions and the analysis was appropriate. |
Low risk of bias |
Data for this outcome was available for all 80 participants randomized. |
Low risk of bias |
The measurement of the outcome was appropriate and it is unlikely that it differed between intervention groups. The outcome assessors were aware of the intervention received, but it is unlikely that knowledge of intervention received could have affected outcome measurement. |
Low risk of bias |
The data that produced this result was analysed in accordance with the predefined outcomes stated in the trial registration. |
Some concerns |
For the outcome "mortality at up to day 28" in this study, there is a low risk of bias due to deviations from intended interventions, due to missing outcome data, in measurement of the outcome and in selection of the reported result. There are some concerns for bias from the randomization process. |
