Key elements of principal investigators at each recruiting site involved in multicenter clinical trials to be disclosed in a publicly open clinical trial registry such as ClinicalTrials.gov.

If there is more than one principal investigator in a site all the information should be provided on all of them.aMultiple locations may be specified on ClinicalTrials.gov. Currently, when provided, the name (and contact details) of a contact person (not necessarily the site principal investigator) is usually given. On the other hand, there are examples in which contact details of all site principal investigators are provided: these are multicenter clinical trials sponsored by, for instance, nonprofit organizations (e.g., NCT01264445), governmental institutions (e.g., NCT01108614), research foundations (e.g., NCT00662220), industry (e.g., NCT00944905), universities (e.g., NCT00973154), collaborative groups (e.g., NCT00209209), or hospitals (e.g., NCT00756600) [6].bDue to early achievement of the number of (randomized) participants needed in the clinical trial.cWhen the trial is terminated, for whatever reason, before completing the expected recruitment. Currently ClinicalTrials.gov allows inclusion of information regarding suspended, terminated, or withdrawn studies providing “a brief explanation of why the study has been halted or terminated. If desired, use brief summary or detailed description to provide additional information. (Limit: 160 characters)” [6].