Hello Roberto,

Regarding your question, registration of observational studies not mandatory, but I advise you to register it. You can follow the instructions in the attached link: https://bit.ly/2t130EQ

Best wishes.

Hi Roberto,

It is not a prerequisite for publication (up until now). However, I am aware of observational studies registered at Clinical Trials registry. Check an example: https://clinicaltrials.gov/ct2/show/NCT00512109

Regards

You may register the the study before trial, but observational study is your finding which is come from the your research and any other sources .

Sss must register

Thanks everybody

Yes, Every clinical trial has to be registered. Observational studies the clinical trial designs.