NIH and FDA have different definitions of clinical trial, please review the Glossary definitions linked below. When a study meets the NIH definition of clinical trial, the study must be registered on ClinicalTrials.gov by the PI or sponsor. OPRS can assist PIs with the registration, but it is the PI's responsibility to ensure their study is registered on ClinicalTrials.gov if it meets the definition.
Contrary to popular belief, the NIH definition of clinical trial does not include investigational drugs or devices and may even be a social/behavioral science project.
The NIH provides guidance and decision tools to assist with understanding if your project meets the definition of a clinical trial.