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 from the protocol: "Subjects are randomly assigned to the experimental group (conventional treatment combined with convalescent plasma treatment group) or the control group (conventional treatment group) according to the ratio of 1: 1, and receive according to the treatment plan of this group treatment. In this study, the randomization was stratified based on the severity of COVID-19 (severe or life-threatening) and a randomization schedule was generated for each type of COVID-19 by SAS software. After completing all the screening and evaluation items in this study, the subjects who meet the eligibility criteria will be assigned a random number according to the randomization schedule. This random number will connect the subject to the designated treatment group (experimental group or control group) for treatment. The randomized subject will withdraw the random number of the subject regardless of any reason. Staff responsible for randomization will only be responsible for the assignment of random groups and will not be involved in any specific trial operations."
Comment: Allocation sequence random. Allocation sequence concealed. |
| Deviations from intervention |
Some concerns |
Comment: Unblinded study (participants and personnel/carers).
Deviations from intended intervention arising because of the study context: No participant cross-over Administration of co-intervention of interest: antivirals (antiviral: 89.1% vs 89.8%, interferon: 26.1% vs 14.3%), corticosteroids (45.7% vs 32.7%) and biologics (28.3% vs 22.5%) were reported. This deviation was not balanced and could affect the outcome. Nevertheless, this domain was rated as some concern as it is impossible to distinguish deviation because of trial context and deviation because of intervention effect. 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 some concerns for the outcomes: Mortality (D28). Time to death. Incidence of viral negative conversion (D7). Clinical improvement (D28). Time to clinical improvement. Adverse events. Serious adverse events. |
| Missing outcome data |
Some concerns |
Comment: 103 participants randomized; 103 participants analyzed for all outcomes except for viral negative conversion (87 participants analyzed).
Data available for all or nearly all participants randomized except viral negative conversion. Risk assessed to be low for the outcomes: Mortality (D28). Time to death. Clinical improvement (D28). Time to clinical improvement. Adverse events. Serious adverse events. Data not available for all or nearly all participants randomized for viral negative conversion outcome. No evidence that the result is not biased. Reasons for missing data: unknown No information on whether missingness could depend on the true value of the outcome. Not likely that missingness depended on the true value of the outcome (similar proportion of missingness between arms). Risk assessed to be some concerns for the outcome: Incidence of viral negative conversion (D7). |
| 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 and viral negative conversion are observer-reported outcomes not involving judgement. Risk assessed to be low for the outcomes: Mortality (D28). Time to death. Incidence of viral negative conversion (D7). Clinical improvement (defined as discharge or a reduction of 2 points on a 6-point disease severity scale) requires clinical judgement and could be affected by knowledge of intervention receipt. Also, the authors reported on adverse events and serious adverse events that may contain both clinically- and laboratory-detected events. All these outcomes can be influenced by knowledge of the intervention assignment, but is not likely in the context of the pandemic. Risk assessed to be some concerns for the outcomes: Clinical improvement (D28). Time to clinical improvement. Adverse events. Serious adverse events. |
| Selection of the reported results |
Some concerns |
Comment: The protocol, statistical analysis plan and trial registry were available.
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). Incidence of viral negative conversion (D7). Time to clinical improvement. Adverse events. Serious adverse events. Time to death and clinical improvement events outcomes were not pre-specified in the protocol, SAP or registry. No information on whether the result was selected from multiple outcome measurements or analyses of the data. Trial probably not analyzed as pre-specified for these outcomes. Risk assessed to be some concerns for the outcomes: Time to death. Clinical improvement (D28). |
| Overall risk of bias |
Some concerns |