World Journal of Surgery | 2021
Faster than Frozen: Promising Preliminary Data for Rapid Parathyroid Tissue Confirmation Via a Novel Point-of-Care Method
Abstract
Intraoperative methods to confirm the presence of parathyroid tissue can optimize outcomes for patients undergoing surgery for hyperparathyroidism as well as help prevent total thyroidectomy-induced hypoparathyroidism by guiding parathyroid autotransplantation. Several adjuncts for intraoperative confirmation of parathyroid tissue have been described, including frozen section analysis, intraoperative parathyroid aspiration with parathyroid hormone (PTH) assay testing, and radioguided parathyroid surgery. While frozen section analysis by a pathologist can differentiate parathyroid from non-parathyroid tissue and may offer further characterization of the tissue, it may be time-consuming relative to case duration, it relies on the availability of an on-site pathologist, and is not readily available at many surgery centers across the world. Aspiration of a suspected parathyroid gland with subsequent intraoperative PTH assay analysis can reliably identify parathyroid tissue [1] but may delay an operation depending on the rapidity of the institutional assay and is also not readily available worldwide. Radioguided surgery may be helpful in confirming hyperfunctioning parathyroid tissue [2], however would not be used to confirm normocellular parathyroid tissue during thyroidectomy. In this issue of the World Journal of Surgery, Kikumori et al. demonstrate the feasibility of quantifying aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) in tissue suspensions using a point of care testing device (NX500, Fujifilm, Japan), and then using the AST/LDH ratio to distinguish parathyroid tissue from non-parathyroid tissue such as thyroid, adipose tissue and lymph nodes [3]. They are able to confirm parathyroid tissue with 100% sensitivity and specificity during both thyroid and parathyroid operations using a cut-off AST/LDH ratio of 0.48, and report that the device has an estimated turnaround time of 10 minutes. These data build on previous work by Kikumori et al. demonstrating similar outcomes of the AST/LDH ratio to distinguish parathyroid tissue (both normal and hyperfunctioning) from non-parathyroid tissue using a lab-based assay. The authors suggest that the AST/ LDH ratio is likely higher in parathyroid tissue because it is rich in mitochondria and thus harbors high levels of enzymes involved in the Krebs cycle such as AST [4, 5]. Although their case numbers are small and limited to a single institution, their body of work to date is clinically applicable and compelling. Moving forward, this method and device require validation at multiple institutions with a large number of cases. It will also be important to directly compare this method with frozen section analysis in terms of turnaround time and accuracy, acknowledging that this quick biochemical test would be solely confirmatory in nature and would not have the capacity to differentiate normal from hyperfunctional parathyroid tissue or offer further characterization of the histology (i.e. hypercellular, atypical, normocellular, etc.). It will also be helpful to evaluate the costs of this method including the device itself (quoted at less than $20,000 in developing countries), associated device maintenance costs, and processing costs, and then compare the expenditures to that of frozen section analysis. And, it is also important to keep in mind that experienced parathyroid surgeons can usually be confident in identifying parathyroid tissue based on gross appearance without any adjuncts. Although there are ample opportunities for further study, we applaud the authors for introducing a simple, & Richard A. Hodin [email protected]