Near-Infrared Autofluorescence Boosts Thyroidectomy Outcomes

Marlene Busko, for Medscape

August 10, 2022

The study covered in this summary was published on Research Square as a preprint and has not yet been peer reviewed.

Key Takeaways

  • In a single-center, case-control study, 134 patients who underwent total thyroidectomy (TT) were compared with patients who underwent conventional (naked eye) surgery. For those who underwent surgery that employed near-infrared autofluorescence (NIR-FA) imaging, the following results were reported:

    • Parathyroid hormone (PTH) levels were higher in the first 3 days after surgery (short term), at the first-month routine postoperative follow-up exam (medium term), and 6 months after surgery (long term) — likely because of less damage to parathyroid glands.

    • There was less short-term postoperative hypocalcemia and hypoparathyroidism.

    • There was less postoperative need for calcium supplements.

Why This Matters

  • Postoperative hypocalcemia secondary to hypoparathyroidism accounts for more than half of complications of thyroid surgery.

  • It is challenging to avoid damage to the parathyroid glands during TT. These glands are damaged or are inadvertently removed in a substantial number of TT cases.

  • Conventional means for reducing the risk of postoperative hypocalcemia focus on the surgeons' experience visualizing parathyroid glands during surgical dissection, but this is subjective, is not always accurate, and can result in an accidental excision or devascularization of one or more glands. In studies of other strategies to overcome the limitations of naked-eye inspection of parathyroid glands during thyroidectomy, there has been a lack of direct evidence of benefit, and the sensitivity of the studies has been low. In addition, the approaches are invasive.

  • NIR-FA can provide real-time images of the surgical field on a high-definition screen, highlighting the position of parathyroid glands and allowing their identification and preservation. NIR-AF is safe, noninvasive, and involves no drugs, which eliminates the possibility of adverse drug effects.

  • Previous studies of the use of NIR-FA during thyroidectomy focused on anatomic outcomes. The current study evaluated postoperative function on the basis of PTH and calcium levels. It is one of the first studies in Italy to report 6-month outcomes for hypocalcemia and hypoparathyroidism.

  • Decreased postoperative need for calcium supplements may decrease public healthcare cost and improve patients' quality of life.

Study Design

  • This was a case-control study that involved 134 patients who underwent total thyroidectomy at San Raffaele Hospital in Milan from January 2020 to June 2022.

  • Half of the patients underwent conventional thyroidectomy, and half underwent thyroidectomy that was assisted by NIR-FA and was performed by surgeons with similar training.

  • Study outcomes were between-group differences in short-term (1 to 3 days), medium term (1 month) and long-term (6 months) postoperative serum calcium and PTH levels; surgical times; need for oral calcium supplements during hospital stay; short-, medium-, and long-term hypocalcemia and hypoparathyroidism; preoperative to postoperative change in serum PTH and calcium levels; and safety outcomes, including the surgeon's confidence and ability to identify parathyroid glands.

  • Hypocalcemia was defined as total calcium <2.1 mmol/L or ionized calcium <1.18 mmol/L or both. Hypoparathyroidism was defined as serum PTH <15 pg/mL. The authors considered patients to have hypocalcemia if the total calcium level was <2.1 mmol/L, the ionized calcium level was <1.1 mmol/L, or the PTH level was <15 pg/mL.

Key Results

  • The study enrolled 67 patients who underwent conventional total thyroidectomy and 67 patients who underwent total thyroidectomy with addition of NIR-AF for benign or malignant conditions. The follow-up period was 1–6 months.

  • The average age of the patients was 52 years, and 75% were women.

  • Among the patients who were treated using NIR-FA, the surgeons identified the parathyroid gland in 55% of cases by examination only and then confirmed the finding with NIR-FA. They identified the gland exclusively with NIR-FA in 34% of cases. In the remaining 11%, the surgeons were unable to find the parathyroid gland.

  • During postoperative days 1–3, significantly fewer patients who underwent thyroidectomy with NIR-FA had hypoparathyroidism: 25% had hypoparathyroidism, compared with 57% among those who underwent conventional surgery; 31% experienced hypocalcemia, compared with 57%. There were no significant between-group differences for these outcomes after 1 month and 6 months.

  • Patients who underwent thyroidectomy with NIR-FA had significantly higher PTH levels after short- and medium-term follow-up, and there were significantly lower variations from baseline in PTH levels at short-term, medium-term, and long-term follow-up.

  • Among patients treated with the use of NIR-FA, the need for short-term oral calcium supplements after surgery was significantly reduced: 37% needed a supplement, compared with 70% among the control patients.

  • There was no significant difference in the duration of surgery between the two subgroups.


  • This was a retrospective study with a relatively small number of participants.

  • The study excluded patients who underwent thyroidectomy with intraoperative indocyanine green angiography, because the authors believe that this method requires a longer learning curve, which could bias findings regarding postoperative PTH and calcium levels.

  • Although the thyroidectomies were performed by the same surgical team, they were not all performed by the same surgeon.

  • The authors cited several limitations of NIR-AF itself: adipose tissue can reduce the fluorescence of parathyroid glands; the technology cannot distinguish between vascularized and devascularized glands; false positive findings may occur for patients with thyroiditis; and the surgeon can only see the surgical field through a screen, not directly.


  • The study did not receive commercial funding.

  • The authors have disclosed no relevant financial relationships.

This is a summary of a preprint research study, "The Impact of Near-Infrared Autofluorescence on Postoperative Hypoparathyroidism During Total Thyroidectomy: A Case-Control Study," written by researchers primarily from San Raffaele Hospital in Milan, published on Research Square, and provided to you by Medscape. This study has not yet been peer reviewed. The full text of the study can be found on

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