<qa>  What is the key to link the unique reference number to the patient?All data collected on the electronic case report forms eCRF for this registry will be de-identified. Each patient will be assigned to a unique reference number. eCRFs are confidential documents and will only be available to the Sponsor including Sponsor delegates, like clinical research associates CRAs, the Investigator, the investigation statistician, and if requested to the advisory committee, ethical committees and regulatory authorities. The key to link the unique reference number to the patient will be kept in the investigation file by the Principal Investigator for each investigation site. 