Criteria for assessing data quality
| Quality level | Criteria |
|---|---|
| Method for exposure measurement | |
| High | Urinary sodium excretion by 24-hour urine collection and high quality of urine collection |
| Low | Urine spot test or questionnaire |
| Unclear | Insufficient information to permit judgement |
| Method and setting for measurement of outcome | |
| High | Measured multiple times, by trained professional and using standardised procedures. If measured by oscillometric method, the device is clinically validated. |
| Low | Otherwise (if not all criteria mentioned above are met) |
| Unclear | Insufficient information to permit judgement |
| External validity | |
| High | Characteristics of study population are relatively representative of, and generalizable to, the general population |
| Low | Characteristics of study population are present in only a specific part of the population (eg, hypertensive children, obese children, etc) |
| Unclear | Insufficient information to permit judgement |
| Reporting | |
| High | Complete report and if applicable trial registration |
| Low | Incomplete report (eg, not all prespecific primary outcomes are reported), source of financial support is missing or impartial |
| Unclear | Insufficient information to permit judgement |