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In situ hybridization: more harmony across checklists

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Anne Paxton

August 2016—As the use of in situ hybridization (ISH) expands, laboratories employing this form of testing increasingly rely on the CAP Laboratory Accreditation Program checklist for guidance. That is one reason members from three CAP committees started meeting to revise the ISH checklist, says CAP Surgical Pathology Committee member Aleodor Andea, MD, MBA. Another reason: to harmonize and streamline the ISH checklist requirements across three different disciplines.

Members from the Surgical Pathology Committee, the Cytogenetics Resource Committee, and the Molecular Oncology Committee formed an ISH/FISH project team in 2015 to produce the revisions in the 2016 ISH checklists, released in August.

Dr. Andea

Dr. Andea

“Historically ISH was performed only in cytogenetics labs, and, as a consequence, the cytogenetics checklist contains the most comprehensive section for ISH,” says Dr. Andea, an associate professor and director of the dermatopathology molecular diagnostics laboratory at the University of Michigan School of Medicine. “However, in the modern era, anatomic pathology labs that have an adjacent immunohistochemistry lab have implemented FISH and chromogenic ISH tests in their environment.” It started mainly with FISH HER2 testing for breast carcinoma, he says, but the ISH menu has quickly expanded to other areas including infectious diseases, soft tissue, solid organs, skin, and cytology, to name just a few. “And then the molecular sections of pathology have also started doing their own FISH in addition to PCR and sequencing.”

Thus, three specialized laboratories in pathology—cytogenetics, anatomic pathology, and molecular pathology—are now performing ISH-related tests, each with its own checklist containing ISH sections that have different requirements, Dr. Andea says, and it has been confusing at times for laboratories to choose which checklist to use. “If you already have a histology lab and you want to do ISH, you would probably select the anatomic pathology checklist. However, for a newly established lab performing mostly FISH testing, the choice would be less clear. I was confronted with this myself when, as director of our dermatopathology molecular diagnostic laboratory, I had to select a checklist dealing with ISH for our new FISH test for melanoma. Eventually we used the cytogenetics checklist because it was the most comprehensive, but we could have used any of the other two.”

Since the three disciplines are performing more or less the same tests, Dr. Andea says, the project team’s goal in the 2016 revisions was to look at the three separate checklists and design one that would fit all of them and be inclusive.

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