An invasive procedure is one in which the body is "invaded", or entered by a needle, tube, device, or scope.
Some procedures routinely employed in clinical practice that are "minimally invasive" can be deemed to pose minimal physical risk to research participants: most commonly, blood draw by venipuncture or specimen collection by nasopharyngeal swab. Risk determination depends also on other contextual features of the study.
OHRP's Secretary’s Advisory Committee on Human Research Protections (SACHRP) offers suggested examples of "minimally invasive" procedures in a 12/2017 Recommendation on revisions to the list of "Expedited categories":
4. Prospective collection of biological specimens, excluding blood, for research purposes by minimally invasive means and not requiring sedation for research purposes.
Examples: (a) tissues from non-facial, non-genital skin punch biopsy with allowable local anesthesia and limited to 2mm in diameter and not requiring sutures; (b) Specimens collected by swab (nasal, oral, urethral, vaginal, rectal); (c) teeth if routine patient care indicates a need for extraction.
SACHRP recommendations are not regulation-level, nor current official guidance from OHRP, but are often considered a reasonable basis for institutional guidance and policy.