FDA final guidance clarifies whole slide imaging expectations in nonclinical toxicology studies

The US Food and Drug Administration (FDA) on Tuesday issued final guidance on the use of whole slide imaging in nonclinical toxicology studies. The guidance is in a question-and-answer format and addresses issues such as validating the whole slide imaging system and protecting the integrity of the images captured.

“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 [good laboratory practice] GLP regulations,” the guidance states.

Histopathological assessment of tissues samples using whole slide imaging is a major part of nonclinical laboratory studies that can help sponsors and regulators understand the toxicology of a drug.

“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,” said FDA. “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.”

The guidance elaborates on those processes and procedures. For instance, the agency says that if whole slide images are assessed in lieu of the original glass slides and result in the generation of pathology raw data, the whole slide image files should be retained as study records and archived. Furthermore, sponsors should ensure that the archived digital images are still viewable as the hardware and software used for viewing the images are updated.

The agency also says that the glass slides containing the study specimens should be retained according to regulation after the study is completed. “Adequate documentation is critical,” the agency writes.

The guidance also addresses issues about how to handle the digital files from the whole slide imaging. For instance, the agency says the software and hardware in the whole slide imaging system used to generate raw data should be validated. The data also needs to be protected to prevent loss or alteration of data during transmission, and sponsors should ensure that they maintain chain of custody, control access, and secure data systems and data transmission.

The Center for Drug Evaluation and Research (CDER) listed the final guidance as part of their 2022 list of priority guidances. The agency posted a draft guidance soon thereafter in April 2022. (RELATED: CDER unveils 30 new planned guidance documents in 2022 agenda, Regulatory Focus 7 February 2022)

Final guidance

FDA final guidance clarifies whole slide imaging expectations in nonclinical toxicology studies

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