| Bias | Author's judgement | Support for judgement |
| Confounding |
Moderate |
Comment: The confounders of interest (age, sex, comorbidities, ethnicity) were controlled for in the propensity score model. Obesity and severity was not included. Of note the HCQ model differs from that of HCQ+ AZM. Quote: "The final propensity-score model for hydroxychloroquine included the first 15 of these factors. That for hydroxychloroquine plus azithromycin included the first 5 of these factors plus cancer." (See supplementary file SAP) |
| Selection of participants into the study |
Moderate |
Comment: Follow up for the outcome of interest begins from time of hospital admission. Quote Hydroxychloroquine and hydroxychloroquine plus azithromycin were evaluated from day of hospital admission, whether initially in the ICU or not. The control population consisted of patients who never received the respective treatment. Comment : It is unclear whether start of the intervention co-incided with start of follow up. For patients who received HCQ after baseline admission time, the time period in which they did not receive anticoagulation should be classified in the non-exposed group (risk of immortal time bias). |
| Intervention classification |
Low |
Comment: Data were collected from electronic health records. Treatment groups were classified using clearly defined criteria.Quote: Exposure to hydroxychloroquine or azithromycin was defined as documentation of drug administration in the EHR. Dosing, duration, and timing in relation to symptom onset and admission were also collected. If no evidence of administration of drug was found, this was recorded as not having received the drug. |
| Deviation from intended intervention |
NI |
Comment: The information reported is inadequate to assess whether there are deviations from the intended intervention beyond what would be expected in usual practice. |
| Missing data |
Low |
No missing data |
| Measurements of outcomes |
Low |
Comment: Observer-reported objective outcome (death). |
| Selection of the reported results |
Moderate |
Comment: The outcomes and analyses are clearly defined in the Methods section. There is no a-priori registered protocol or statistical analysis plan available. |