Autofluorescence alone is not enough: a combined strategy for accurate identification of parathyroid tissue in thyroidectomy specimens

Importance: Inadvertent excision of parathyroid glands (PTGs) during thyroidectomy remains a common and significant surgical complication, potentially leading to hypoparathyroidism. While near-infrared autofluorescence (NIRAF) imaging enhances intraoperative PTG identification, its specificity and real-world diagnostic accuracy remain uncertain. Objective: To evaluate the diagnostic accuracy of NIRAF imaging in identifying inadvertently excised PTGs in thyroidectomy specimens and to assess the added value of intraoperative tissue parathyroid hormone (PTH) washout testing. Design, Setting, and Participants: This was a prospective diagnostic accuracy study conducted at a university hospital between 28 February 2024, and 28 February 2025. Consecutive adult patients undergoing conventional or endoscopic thyroidectomy were included. NIRAF imaging was performed on all excised thyroid lobes prior to pathological examination. Autofluorescent (AF)-positive areas were assessed using intraoperative tissue PTH washout testing, with histopathology serving as the reference standard. Main Outcomes and Measures: The primary outcome was the diagnostic performance (sensitivity, specificity, positive predictive value [PPV], and negative predictive value [NPV]) of NIRAF imaging for identifying parathyroid tissue. Secondary outcomes included inadvertent parathyroid excision rate and diagnostic accuracy of the tissue PTH washout test. Results: Among 672 patients (mean age, 46.8 years; 82.7% female), 1,144 thyroid lobes were examined, yielding 224 AF-positive areas. Of these, 197 had PTH ≥100 pg/mL and were confirmed as PTGs; 27 had PTH <100 pg/mL, of which 2 were confirmed as PTGs on histopathology. The sensitivity and specificity of NIRAF imaging were 100.0% (95% CI, 98.1%–100.0%) and 97.9% (95% CI, 96.7%–98.7%), respectively; PPV was 88.8% and NPV was 100.0%. The inadvertent parathyroid excision rate was 8.7% (199/2,288). The tissue PTH washout test showed 99.1% overall diagnostic accuracy (95% CI, 97.3%–99.8%), with sensitivity 99.0% (95% CI, 96.2%–99.9%), specificity 100.0% (95% CI, 86.3%–100.0%), PPV 100.0% (95% CI, 98.1%–100.0%), and NPV 92.6% (95% CI, 75.7%–98.9%). Conclusions and Relevance: NIRAF imaging is highly sensitive for detecting inadvertently excised parathyroid glands, but false-positive signals from non-parathyroid tissues limit its specificity. Combining NIRAF with intraoperative tissue PTH measurement can improve diagnostic accuracy and guide timely autotransplantation. Further studies are needed to refine tissue PTH thresholds and validate broader clinical applicability.