DNA Yield From Tissue Samples in Surgical Pathology and Minimum Tissue Requirements for Molecular Testing.

CONTEXT: Complex molecular assays are increasingly used to direct therapy and provide diagnostic and prognostic information but can require relatively large amounts of DNA. OBJECTIVES: To provide data to pathologists to help them assess tissue adequacy and provide prospective guidance on the amount of tissue that should be procured. DESIGN: We used slide-based measurements to establish a relationship between processed tissue volume and DNA yield by A260 from 366 formalin-fixed, paraffin-embedded tissue samples submitted for the 3 most common molecular assays performed in our laboratory (EGFR, KRAS, and BRAF). We determined the average DNA yield per unit of tissue volume, and we used the distribution of DNA yields to calculate the minimum volume of tissue that should yield sufficient DNA 99% of the time. RESULTS: All samples with a volume greater than 8 mm(3) yielded at least 1 µg of DNA, and more than 80% of samples producing less than 1 µg were extracted from less than 4 mm(3) of tissue. Nine square millimeters of tissue should produce more than 1 µg of DNA 99% of the time. CONCLUSIONS: We conclude that 2 tissue cores, each 1 cm long and obtained with an 18-gauge needle, will almost always provide enough DNA for complex multigene assays, and our methodology may be readily extrapolated to individual institutional practice.

Rhodococcus fascians infection after haematopoietic cell transplantation: not just a plant pathogen?

INTRODUCTION: Rhodococcus spp. have been implicated in a variety of infections in immunocompromised and immunocompetent hosts. Rhodococcus equi is responsible for the majority of reported cases, but Rhodococcus erythropolis, Rhodococcusgordoniae and Rhodococcusruber infections have been described. There are no prior reports of human infection with Rhodococcus fascians. CASE PRESENTATION: We describe the unexpected finding of R. fascians in liver lesions incidentally noted at autopsy in an immunosuppressed patient status after bone-marrow transplant for acute lymphoblastic leukaemia who died of unrelated causes (septic shock due to Clostridium difficile colitis). At autopsy, an otherwise unremarkable liver contained several dozen well-demarcated sclerotic-appearing lesions measuring 0.1-0.3 cm in size. The absence of other bacterial or fungal DNA in the setting of histologically visible organisms argues against its presence as a contaminant and raises the consideration that R. fascians represents a human pathogen for the immunocompromised. CONCLUSION: Whether it represents the sole infectious agent responsible for the miliary lesions or a partially treated co-infection is impossible to determine, but our finding continues to reinforce the importance of molecular techniques in associating organisms with sites of infection and optimizing treatment of infectious diseases.

Progressive Independence in Clinical Training: Perspectives of a National, Multispecialty Panel of Residents and Fellows.

BACKGROUND: Progressive independence in patient care activities is imperative for residents' readiness for practice and patient safety of those cared for by graduates of residency programs. However, establishing a standardized system of progressive independence is an ongoing challenge in graduate medical education. OBJECTIVE: We aggregated trainees' perspectives on progressive independence, developed a model of the ideal state, and suggested actionable improvements. METHODS: A multispecialty, nationally representative group of trainees conducted a structured exercise that (1) described the attributes of an ideal system of graduated responsibility; (2) compared the current system to that ideal; (3) developed benchmarks to reinforce best practices; and (4) identified approaches to motivate programs to adopt best practices. RESULTS: At the core of an ideal model of graduated responsibility is a well-structured curriculum and assessment of individual learners using educational milestones and patient outcomes. The ideal model also includes robust faculty development and emphasizes faculty mentorship. To address legal and financial restrictions that pose barriers to progressive independent, objective outcome criteria like the milestones could be used to ask payers to alter payment restrictions for work performed by senior trainees, providing financial incentives for programs to encourage appropriate independent practice. Recognition of high-performing programs at the national level could motivate others to adopt best practices. CONCLUSIONS: A multifaceted approach, incorporating robust 2-way feedback about skill level and autonomy between residents and faculty, along with improved faculty development in this area, is needed to optimize residents' attainment of progressive independence. There are incentives to move programs and institutions toward this optimal model.