Importance: Intrinsic near-infrared (NIR) autofluorescence of the parathyroid gland enables intraoperative gland identification without the need for contrast agent injection. However, whether real-time autofluorescence imaging is useful in patients with multiple endocrine neoplasia type 1 (MEN1) and primary hyperparathyroidism is unknown.
Objective: To compare quantified intraoperative parathyroid autofluorescence imaging results for patients with MEN1-associated vs those with non-MEN1 sporadic primary hyperparathyroidism.
Design, setting, and participants: A retrospective analysis of prospectively collected data on a cohort of 71 consecutive patients undergoing surgery for primary hyperparathyroidism by 2 experienced endocrine surgeons between June 1, 2017, and July 31, 2018, was conducted. Intraoperative imaging was performed with a handheld NIR autofluorescence device and images were captured for analysis. Post hoc blinded imaging analysis was conducted with Image J software to quantify representative areas of greatest autofluorescence from the parathyroid, thyroid, and adjacent soft tissue.
Main outcomes and measures: Primary end points were parathyroid autofluorescence and background thyroid and soft tissue autofluorescence, reported as median values with interquartile ranges. Rates of false-negative (lack of significant parathyroid gland autofluorescence compared with background autofluorescence, defined as parathyroid autofluorescence-background autofluorescence ratio <1.10) and false-positive autofluorescence (aberrant autofluorescence of nonparathyroid tissue confirmed by pathologic testing) were analyzed.
Results: Of the 71 consecutive patients with primary hyperparathyroidism who underwent parathyroidectomy during the study period, 6 patients had genetically or clinically diagnosed MEN1 and 65 had sporadic non-MEN1 hyperparathyroidism. Most patients were women (MEN1: 4 [67%]; non-MEN1: 51 [78%]). Median (interquartile range) age was 49.0 (38.0-53.8) years in the MEN1 cohort and 61.0 (54.0-67.0) years in the non-MEN1 cohort. No clinically significant differences in serum preoperative parathyroid hormone level or parathyroid gland size or weight on pathologic examination were observed between the 2 cohorts. The median absolute value of in situ parathyroid autofluorescence was significantly lower in the MEN1 cohort than the non-MEN1 cohort (54.4 vs 74.3; Hedges g = -1.03; 95% CI, -1.89 to -0.17), as was the ratio of parathyroid to background autofluorescence (1.08 vs 1.59; g = -1.59; 95% CI, -2.23 to -0.96). Three patients (50%) with MEN1 had false-negative nonfluorescent parathyroid adenomas vs 6 patients (9%) without MEN1. Nonparathyroid fibroadipose tissue of patients with MEN1 exhibited greater background autofluorescence, leading to high false-positive rates (5 of 6 patients [83%]) vs only 3 of 65 (5%) false-positive autofluorescence nonparathyroid specimens among patients without MEN1.
Conclusions and relevance: Intraoperative identification of parathyroid glands using their autofluorescence by real-time NIR imaging appears to have utility in patients with primary hyperparathyroidism. In this initial cohort of patients with MEN1, decreased parathyroid autofluorescence and increased background autofluorescence of nonparathyroid tissue may be associated with high rates of false-negative and false-positive fluorescence, potentially limiting the utility of this adjunct in this specific subset of patients.