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

To learn more about whole slide imaging in nonclinical toxicology studies, read the guidance.

www.fda.gov 1

Use of Whole Slide Imaging in Nonclinical 

Toxicology Studies: Questions and Answers 

Final Guidance for Industry

What is Covered

in this guidance?

This guidance provides information to sponsors 

and nonclinical laboratories regarding the use and 

management of whole slide images used during 

histopathology assessment and/or pathology peer 

review performed for good laboratory practice 

(GLP)-compliant nonclinical toxicology studies.

Why is this 

Guidance important?

The histopathological assessment of tissue samples 

is one of the key activities conducted during GLPcompliant nonclinical laboratory studies. Commonly, 

the histopathological assessment includes an initial 

evaluation of glass histology slides by the study 

pathologist and a subsequent review (referred to 

as pathology peer review) by a second pathologist, 

group of pathologists, or Pathology Working Group. 

When whole slide imaging is used as part of a 

nonclinical study conducted in compliance with the 

GLP regulations, the management, documentation, 

and use of whole slide images in histopathology 

assessment and/or pathology peer review should be 

clear and follow written processes and procedures.

What Is Addressed in this Guidance?

Among the topics addressed in this guidance:

 Whether whole slide images should 

be retained.

 Whether written procedures for whole slide 

imaging processes should be in place.

 Whether the whole slide imaging system 

should be validated.

Guidance Snapshot
www.fda.gov

Guidance Recap Podcast

Hear highlights from FDA staff

Click here to listen Click here to 

read transcript

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

To learn more about whole slide imaging in nonclinical toxicology studies, read the guidance. To see 

additional Guidance Snapshots, check out the pilot program.

2

Speaker(s): Lynda Lanning, DVM, DABT, Toxicologic Pathologist in the Center for Drug Evaluation 

and Research’s Office of Study Integrity and Surveillance

Drug Development Timeline

* When to Apply the Guidance Recommendations

Background About the Guidance

This guidance finalizes draft guidance issued 

in April 2022 titled Use of Whole Slide Imaging 

in Nonclinical Toxicology Studies: Questions 

and Answers. The FDA’s expectations regarding 

documentation practices during generation, 

use, and retention of whole slide images have 

not been clearly defined, and thus, documentation 

practices vary among nonclinical testing facilities. 

This question-and-answer document is intended 

to clarify FDA’s recommendations concerning the 

management, documentation, and use of whole slide imaging 

in histopathology assessment and/or pathology peer review for 

nonclinical studies conducted in compliance with the GLP regulations.

PHASE 2 PHASE 3

FDA 

FILING & 

APPROVAL

BASIC 

RESEARCH

PROTOTYPE 

DESIGN OR 

DISCOVERY

PRECLINICAL 

DEVELOPMENT*

POSTMARKET OR 

POSTAPPROVAL 

STUDIES

CLINICAL 

DEVELOPMENT

PHASE 1

During Preclinical Development: This guidance provides information regarding the use and 

management of whole slide images used during histopathology assessment and/or pathology 

peer review performed for good laboratory practice (GLP)-compliant nonclinical toxicology studies 

using non-human specimens. The guidance does not cover the use of whole slide imaging for 

clinical applications.