Guidance Snapshots are a communication tool and are not a substitute for the guidance document. 

To learn more about pathology peer review in nonclinical toxicology studies, read the guidance: 

https://www.fda.gov/media/129533/download

www.fda.gov

Pathology Peer Review in Nonclinical Toxicology Studies: 

Questions and Answers

Final Guidance for Industry

What Is Covered in This Guidance?

The final guidance Pathology Peer Review in Nonclinical Toxicology 

Studies: Questions and Answers provides information to sponsors and 

nonclinical laboratory staff regarding the management and conduct 

of pathology peer review performed during good laboratory practice 

(GLP)-compliant toxicology studies..

What Is Pathology Peer Review, and Why Is It Performed?

Pathology peer review is the process by which the findings of the pathologist assigned to a study (study pathologist) are subjected to review by 

another pathologist (peer-review pathologist) or group of pathologists 

(peer-review pathologists). While pathology peer review is not required by 

the GLP regulations, it can be valuable, particularly when unique or unexpected findings are noted or when the peer-review pathologist has a particular expertise with a class of compounds.

Study Pathologist

Peer-Review Pathologist

Who?

Where?

When?

How?

The peer-review pathologist should 

have a combination of appropriate 

education, training, and experience 

to be qualified to render opinions 

on the study pathologist’s 

histological descriptions. 

Pathology peer review can occur 

before or after finalization of the 

study pathologist’s report. The draft 

pathology report is subject to change 

until the report is signed and 

dated by the study pathologist. 

A pathology peer 

review should be 

planned, conducted, 

documented, and 

reported in accordance with 

established procedures. It is 

preferable that pathology peer review 

be performed at a GLP-compliant 

testing site.

A standard operating 

procedure and GLP 

study protocol (or protocol 

amendments) should include 

a description of the peer-review 

procedure, including the selected 

target tissues, dose groups, number of 

specimens, blinding procedures, and 

the process for resolving interpretive 

differences between the study pathologist 

and the peer-review pathologist.
Guidance Snapshots are a communication tool and are not a substitute for the guidance document.

To learn more about pathology peer review, read the guidance: 

https://www.fda.gov/media/129533/download

To see additional Guidance Snapshots, check out the pilot program: 

https://www.fda.gov/drugs/guidances-drugs/guidance-snapshot-pilot

www.fda.gov

Background About the Guidance 

This guidance finalizes the draft guidance published in July 2019 

titled Pathology Peer Review in Nonclinical Toxicology Studies: Questions and Answers. Currently, documentation practices during pathology peer review are not clearly defined and vary 

among nonclinical testing facilities. In addition, pathology peer 

review is not specifically addressed in the GLP regulations. This 

question-and-answer document is intended to clarify FDA’s recommendations concerning the management, conduct, and documentation of pathology peer review. Casual discussions, opinion 

exchange, and mentoring among pathologists are not covered by 

this guidance.

Drug Development Timeline – When to Apply the Guidance Recommendations

During Nonclinical Toxicology Studies: 

This question-and-answer document is intended to clarify FDA’s recommendations concerning the 

management, conduct, and documentation of pathology peer review that occurs during a nonclinical 

toxicology study under GLP (referred to as a GLP toxicology study).

Guidance Recap Podcast – Hear Highlights Straight From FDA Staff

Speaker: Lynda Lanning, DVM, DABT, Toxicologic Pathologist in the 

Center for Drug Evaluation and Research’s Office of Study Integrity and 

Surveillance

Click here to listen Click here to read transcript