Pre-analytic Workflow and Specimen Evaluation

An optimal pre-analytic workflow is a proactive adaptation to the demands of molecular pathology and takes into account the strengths and weaknesses of one’s practice environment. Ideally, the pre-analytic retrieval, evaluation, and preparation of cases for molecular testing are done efficiently with minimal disruption to conventional diagnostic services and done well to ensure trustworthy test results. Depending on practice environment, the potential need for molecular testing may also impact sample collection and preparation. The first requirement of a proper pre-analytic evaluation is an understanding of the particular platforms used for testing and their analytic requirements. Immunoperoxidase stains and FISH studies are well established. PCR/NGS may be less familiar to the practicing pathologist and the input requirements less understood and more variable. These tests are characterized by two analytic thresholds – input DNA (minimum amount of DNA to obtain a signal) and tumor fraction (minimum percentage of tumor to ensure an observable tumor signal against a wild-type background). A careful pre-analytic evaluation scrutinizes the sample to ensure adequacy for testing and may require tumor mapping to enhance the tumor fraction. Although not intellectually challenging work, this does require great attention to detail, thoroughness, and some self-training. Communication with the clinical team is especially important with marginally adequate samples at risk for a false-negative result and when triaging of multi-test requests is needed because of limited sample.