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Section 8



Federal regulations require review and approval by the IACUC of significant changes in any activity involving the use of animals. Broad interpretation by regulatory officials shows that deviations from approved protocols that seem insignificant to investigators as well as their institutional animal care and use committees have later been determined to be significant by regulatory officials investigating particular incidents. Guidance they provide indicates that it is better to confer beforehand with the IACUC or regulatory officials about what constitutes a significant change rather than after the fact.

The process for modifying (or amending) an existing IACUC application varies depending on the nature of the desired modification. Some modifications are considered routine or minor, and can be reviewed and approved by the IACUC Chairperson and Attending Veterinarian. Other proposed revisions are substantive or major, and must be reviewed either by a Designated Reviewer, or by the Full Committee, using the same process as a new approval. Regardless of the nature of the proposed modifications, all revisions in study procedures must be approved by the IACUC in advance of being implemented by the investigator.

An application may be modified with respect to one or more of the following:

  1. funding;
  2. personnel : investigators, including principal investigator, may change, as may other authorized personnel, or such relevant information as an investigator's contact telephone number;
  3. population : the size of the study population may change, or a new population may be included;
  4. procedures : interventions, or other approved procedures, instruments;
  5. purpose : involving, for example, changes in the time over which the study is conducted.



Major or significant change

The following are examples of major changes that are to be presented to the entire IACUC and the procedure is followed as outlined under the IACUC Review Process. If several major changes occur, it may warrant submission of a new Clearance form.

  1. A change in the overall aim or objective of the study which supports the need to perform the animal work.
  2. A change which may involve an increase in the level of pain, distress, and/or discomfort so as to categorize it in a different USDA category.
  3. An increase in mortality over levels that were either specified or presumed to occur when the protocol was originally reviewed.
  4. A change from non-surgery to surgery; from minor to major surgery; from non-survival to survival surgery, or from single to multiple survival surgery.
  5. A change involving the need for euthanasia, where none had originally been anticipated.
  6. A large (>20%) increase in the number of animals to be used.
  7. A change in the genus.
  8. The addition of a hazardous agent used in the animal procedure.
  9. A change in Principal Investigator.

Minor change

The following are examples of minor changes and may be approved by the Attending Veterinarian and IACUC Chair.

  1. Additions or changes in the personnel who will be performing procedures involving animals, other than the PI.
  2. A small (<=20%) increase in the number of animals to be used.
  3. A minor change in technique, drug, diet, and the like which is not inconsistent with the intent of the original Clearance form, nor does it change the level of discomfort, distress, or pain (remains in the same USDA category).



  1. Investigators should carefully consider whether proposed project modifications are significant. It is common practice to confer with the IACUC Chairperson for guidance in this determination and whether it needs to be approved by the entire IACUC or whether a new Clearance Form is required.
  2. Investigators should complete and submit a Project Modification Request form (available on the website). The modification narrative should thoroughly describe the change(s) and include a justification for the change(s). It may be helpful to refer to the original questions asked on the clearance form. This will help ensure that necessary information needed for a thorough review of the modification is provided to the IACUC.
  3. If the change involves animal use that would be placed in a higher pain/distress classification, you must also include an "Alternatives to Procedures causing Pain and/or Distress" narrative (see question 3 on the Clearance Form) describing the consideration of alternative methods to the painful/distressful procedure(s).
  4. If a new Clearance form is required, it should be complete and include all information (old and new) regarding animal use. Once approved, this new Clearance Form will replace the old Clearance Form.
  5. The IACUC Chair will determine the type of review required and initiate the process.
  6. Investigators must wait for IACUC approval of project modifications before implementing these proposed changes in study procedures.
  7. It is the responsibility of the approving veterinarian and the IACUC Chair to inform the IACUC of changes they have approved.



  1. Study-related procedures, instruments and forms are approved only in the context of a specific IACUC application. Materials that are not reviewed cannot be approved. Only approved study procedures and materials may be implemented by an investigator.
  2. The principal investigator on an IACUC application will not be changed without a signed letter from the current principal investigator assigning the application (i.e., research) to a new principal investigator. In cases where a principal investigator has died or is otherwise unavailable, this letter of assignment may be signed by the chair of the department, dean of the college, or a university vice president, and should include an explanation of the circumstances justifying the change in investigators.

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