Utility of Parathyroid Autofluorescence in Differentiating Parathyroid Pathology

Near-infrared autofluorescence (NIRAF) spectroscopy is an emerging adjunct for intraoperative parathyroid identification. However, its ability to differentiate between normocellular, hyperplastic, or adenomatous parathyroids remains unexplored. We hypothesize that parathyroid adenomas have lower NIRAF ratios than normocellular parathyroids since the likely fluorophore is the calcium-sensing receptor (CaSR), which is downregulated in adenomas.

In vivo NIRAF ratios for each identified parathyroid gland were recorded for patients undergoing thyroidectomy or parathyroidectomy from 08/2023 to 12/2023 at a single institution. Parathyroids were categorized as normocellular by visual inspection and hyperplastic or adenomatous by final histology.

Of the 44 patients included (66% underwent parathyroidectomy and 34% underwent thyroidectomy), 137 parathyroids were identified intraoperatively with 66 resected and analyzed histologically. A total of 71 (52%) parathyroids were normocellular, 45 (33%) were hyperplastic, and 21 (15%) were adenomatous. Among the resected parathyroids, there was moderate agreement (81%) between visual categorization and final histology for hyperplasia versus adenoma (κ = 0.6). Parathyroid adenomas had lower median NIRAF ratios than normocellular parathyroids (p = 0.0005). Median NIRAF ratios were not significantly different between normocellular and hyperplastic parathyroids (p = 0.35) nor between hyperplastic parathyroids and adenomas (p = 0.04). The performance of NIRAF spectroscopy in differentiating parathyroid pathology is poor based on receiver operator characteristics analysis.

Parathyroid adenomas have lower NIRAF ratios than normocellular parathyroids. However, the performance of using NIRAF ratios to differentiate between parathyroid pathology is poor. Therefore, the differences in NIRAF ratios are unlikely to be sufficient at point-of-care use to distinguish between various parathyroid pathologies. As NIRAF ratios are highest in normocellular parathyroid glands, NIRAF appears to be most useful in detecting normal parathyroid glands.