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LOS ANGELES -- Screening with ¹⁸F-fluorocholine PET/CT imaging had the best detection capability for identifying parathyroid adenoma, according to a new study.

Among 30 patients with primary hyperparathyroidism, PET/CT imaging had over a 73% detection rate of parathyroid adenoma -- detecting the tumor in 22 of these patients, reported Franco Grimaldi, MD, of the University-Hospital of Udine in Italy, and colleagues.

This imaging method outperformed ^99mTc-MIBI SPECT/CT, which had a 40% detection rate (12 of 30 patients), and high-resolution neck ultrasound, which had a 60% detection rate (14 of 30 patients).

The findings were reported at , the annual meeting of the American Association of Clinical Endocrinologists.

When using two different diagnostic techniques, all three combinations of two screening methods yielded less than a 50% concordant positive result:

• PET/CT and MIBI: 23.3% (7/3) concordant positive result
• PET/CT and ultrasound: 46.7% (14/30)
• MIBI and ultrasound: 30% (9/30)

Similarly, when using a combination of two different diagnostic techniques, inclusion of PET/CT imaging lessened the frequency of concordant negative results:

• PET/CT and MIBI: 10% (3/30) concordant negative result
• PET/CT and ultrasound: 13.3% (4/30)
• MIBI and ultrasound: 26.7 (8/30)

The analysis included 26 women and four men, average age 61, all with an enlarged or hyper-functioning parathyroid gland with at least two different imaging techniques. Ten patients elected to undergo surgery, nine of whom recovered (defined as normal calcium and parathyroid hormone blood levels after surgery). One patient did not recover following surgery.

Among the entire cohort of 30 patients, average calcium levels were 11. Average baseline parathyroid hormone levels were 183.4 pg/mL; the normal range is 11.1-79.0 pg/mL.

Among all nine patients recovering after surgery, their parathyroid adenomas were detected by PET/CT. On the other hand, MIBI only detected two of these recovery cases, while ultrasound detected the adenoma in six of these patients.

Bone alkaline phosphatase (bALP) levels were significantly higher among patients who had a parathyroid adenoma detected by PET/CT compared with negative cases (34.2±13.4 vs 21.2±3.7), which Grimaldi referred to as an "interesting" finding. "Bone alkaline phosphatase may represent a marker for choosing PET/CT as a first-line imagine technique in primary hyperparathyroidism," he suggested during an oral presentation of the findings, adding that "the role of bALP in predicting positive PET results should undergo further investigations."

As for MIBI and ultrasound, positive and negative cases using these screening methods did not show significant differences in calcium, phosphate, parathyroid hormone, or bALP levels.

Session moderator David Lieb, MD, of Eastern Virginia Medical School in Norfolk, asked whether PET imaging is as readily accessible as the other imaging techniques. Grimaldi acknowledged that PET imaging is "more expensive" but ultimately worth it because of the higher detection capability.

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