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A newly developed handheld probe helped distinguish between thyroid and parathyroid tissues during surgical procedures, according to a diagnostic/prognostic study.

Using real-time mass spectroscopy, MasSpec Pen technology was able to achieve an overall accuracy -- defined as agreement with pathology -- of 92.4% (95% CI 87.7-95.4), reported James Suliburk, MD, of the Baylor College of Medicine in Houston, and colleagues.

The MasSpec Pen correctly classified 91% of thyroid tissues and 94% of parathyroid tissues, the researchers noted in .

Using a training set of 185 mass spectra, including 87 thyroid samples (44 laboratory, 22 in vivo operating room, and 21 ex vivo operating room) and 98 parathyroid samples (61 laboratory, 22 in vivo operating room, and 15 ex vivo operating room), thyroid tissue was able to be distinguished from lymph node tissue with 97.5% accuracy, and parathyroid tissue was distinguished from lymph nodes with 96.1% accuracy.

When using an independent test set comprised of data from 184 remaining intraoperative cases (94 thyroid, 90 parathyroid/81 in vivo, 103 ex vivo), the MasSpec Pen achieved 82.6% (95% CI 76.5-87.4) accuracy -- 86% for thyroid tissues and 79% for parathyroid tissues. There was 78% accuracy for the in vivo analyses and 86% accuracy for ex vivo analyses.

"Accurate intraoperative identification of tissues is critical to surgical practice," Suliburk's group wrote. "During thyroid and parathyroid procedures, visual discrimination of tissues prior to excision can be challenging due to anatomic proximity as well as gross similarities in tissue characteristics, including tactile feel, color, and shape."

The MasSpec Pen allowed surgeons to have an alternative method for identifying tissues in vivo in a nondestructive way before excision, enabling them to only remove diseased tissue and preserve healthy tissue, the authors explained.

In an , Michelle B. Mulder, MD, and Quan-Yang Duh, MD, both of the University of California San Francisco, said that while surgeons can typically visually identify parathyroid glands, sometimes "patient-specific limitations, prior operations, ectopic locations, and concomitant pathology can complicate visual identification even for experienced surgeons."

Calling the pen "an innovative and promising device," the commentators did list a few other FDA-approved noninvasive optical technologies that use near-infrared autofluorescence, which can be probe-based like AiBiomed and Medtronic's or Fluoptics' image-based . However, these devices can sometimes return false positives -- like with brown fat or colloid -- or false negatives, as with limited depth of penetration, Mulder and Duh said.

While the MasSpec Pen can't measure parathyroid gland perfusion and vascularity, they noted this can be measured by indocyanine green angiography, laser Doppler flowmetry, and laser speckle contrast imaging.

Developed by Suliburk's group, intraoperative testing of the MasSpec Pen system was performed at Baylor St. Luke's Hospital in Houston from 2018 to 2020 among 102 patients (median age 52, 78% women). Using a droplet of sterile water in order to gently extract metabolites and lipids from tissues on contact, they used a tip reservoir diameter of 2.7 mm, providing the molecular analysis in about 15 seconds.

Because normal parathyroid and lymph node tissues typically span 1 to 3 mm in diameter, the researchers said they plan to use a smaller pen tip in future assessments, so surrounding tissues aren't accidentally sampled.

Mulder and Duh concluded that as they "appreciate these clinical innovations, it is essential to recognize that no amount of technology can replace the fundamental surgical knowledge and judgment of an expert surgeon required for successful surgical outcomes."

Though not yet FDA approved, the MasSpec Pen has also been tested for detecting , most recently with tumor margins.