Recommendations for future clinical observational studies on post-COVID-19 syndrome

1. Reports should follow all/most STROBE recommendations for observational research, and attach their checklist [24]
2. Minimal follow-up of 6 months
3. Early, active identification of subjects at risk of severe sequelae
4. Use reference groups (i.e.: hospital controls via electronic health records; or population-based controls; or else)
5. Tests, questionnaires and tools to assess patient outcomes should be pre-specified as per a protocol
6. A minimum dataset to merge variables/values/patients in a standard dictionary should be implemented
7. Characterise risk factors known for persistence of symptoms: high blood pressure, overweight/obesity, smoking, mental health conditions, other comorbidities and their treatment, …
8. Recording of real-time data with apps, remote sensors and e-health
9. Assess mental status and post-traumatic stress disorder
10. Assess quality-of-life of patients (and their carers) objectively
11. Identify early potential pharmacological (e.g. steroids) and non-pharmacological (IMV and NIMV, …) adverse events
12. Report at the least three sets of serial measurements over time, to fully assess recovery
13. Use objective techniques, like cardiopulmonary exercise test, to assess the exercise impairment
14. Assess effects of targeted rehabilitation
15. Differentiate from systemic exertion intolerance disease, formerly known as chronic fatigue syndrome (SEID/CFS)
16. Identify laboratory tests or biomarkers to characterise the post-COVID-19 syndrome
17. Assess correlation between symptoms and abnormal peak oxygen consumption