Practical Considerations in the Implementation of Peripheral Smear Review in the Clinical Laboratory

Even in the era of modern automated hematology analyzers, visual peripheral blood smear (PBS) review remains an important component of peripheral blood evaluation in a subset of specimens. Despite published PBS review guidelines, including those issued 20 years ago by the International Consensus Group for Hematology Review (ICGHR), knowledge gaps remain regarding selection and implementation of PBS visual review criteria in clinical laboratories. The purpose of this article, developed by an international working group (the Peripheral Smear Review Working Group [PSRWG]), is to help bridge knowledge gaps by providing practical guidance and items for consideration. PBS review may be indicated for automated analyzer system flags, suspect flags, numerical/definitive flags, or as a component of delta checks. Examples, explanations, and suggestions for each of these categories are provided as are examples of flag modification. Validation of PBS review criteria is a multistep process that includes defining criteria for a positive finding, selecting specimens for study, choosing the slide review method, and determining the statistical approach. Pragmatic approaches and important items to consider are provided for each of these validation steps. PBS visual review workflow must be tailored to the needs of the clinical laboratory/institution. These needs may differ depending on the accrediting agency, laboratory/institutional infrastructure, and population served. A discussion of these variables is provided. In this article, we expand on the proposed ICGHR rules with a discussion of practical considerations in the implementation of PBS review.