Preop Detection of Abnormal Parathyroid Glands Improved With Combination of Ultrasonography and Sestamibi Scintigraphy

Deborah Brauser

October 01, 2009

October 1, 2009 (Palm Beach, Florida) — Performing both high-frequency ultrasonography and technetium 99m-sestamibi scintigraphy (MIBI) scans preoperatively in patients with primary hyperparathyroidism can lead to the finding of more abnormal parathyroid glands than either modality alone, according to a Turkish study presented here at the American Thyroid Association 80th Annual Meeting.

In addition, the investigators found that although sensitivity was much higher with ultrasonography than with MIBI, specificity was less.

The results were reported in a poster presentation by Serhat Işik, MD, from the Endocrinology and Metabolism Clinic at the Ankara Numune Research and Training Hospital in Turkey.

"Parathyroid ultrasonography and technetium 99m-sestamibi scintigraphy are the dominant imaging techniques for preoperative location of parathyroid adenomas," reported Dr. Işik.

In this study, the investigators sought to evaluate the effect of thyroid nodules on the sensitivity of MIBI in patients with parathyroid adenoma.

Dr. Işik and his team evaluated 245 patients (80.8% female; mean age, 55 years) with primary hyperparathyroidism who underwent parathyroidectomy at the Ankara clinic.

All patients received both high-frequency ultrasonography and MIBI scans. The volumes of thyroid lobes and nodules and the number of nodules were assessed.

Combination of Modalities Best for Detecting Abnormal Glands

Results showed that "abnormal parathyroid glands could be localized preoperatively in 224 of the patients by ultrasonography, while MIBI localized these glands in only 144 of the patients," reported Dr. Işik.

The MIBI scan detected 5 cases that were not found by ultrasonography. A total of 85 cases were found by ultrasonography and not by MIBI, 54 of which had thyroid nodules.

When both procedures were used together, only 16 cases of abnormal parathyroid glands went undetected.

In addition, the presence and number of thyroid nodules were significantly higher in patients who did not undergo MIBI scan than in those who did (= .037).

No differences were found in ipsilateral thyroid lobe involvement or nodule volume.

However, the volume of the parathyroid adenoma was significantly less in patients who did not undergo MIBI scan (< .001).

Finally, sensitivity for all cases was much higher for ultrasonography than for MIBI (93.6% vs 60.17%), and specificity was higher for MIBI than for ultrasonography (77.7% vs 66.7%).

"Our results suggest that ultrasonography has high sensitivity in the detection of parathyroid adenomas, but low specificity. And we found that the sensitivity of MIBI scans decreases in low volume adenomas and in the presence of thyroid nodules," concluded Dr. Işik.

Findings Support Change in Preop Evaluation

"I think this is a very good study that demonstrates the changes in surgical technique as we apply them to parathyroid operations," Gerard M. Doherty, MD, professor of surgery and chief of the Endocrine Surgery Division at the University of Michigan Health Systems in Ann Arbor, and secretary-treasurer of the International Association of Endocrine Surgeons, told Medscape Endocrinology. Dr. Doherty was not involved with this study.

"The technique has now changed to a preoperative exploration, where we identify the abnormal thyroid glands with preoperative tests and then plan a focused operation to remove only the affected part," explained Dr. Doherty.

He added that "this study demonstrates the strengths and weaknesses of the 2 main tests that we use to locate parathyroid gland beforehand. The sestamibi scan finds bigger glands better than smaller glands and the ultrasound finds glands that are close to the thyroid gland better than glands that have fallen away. So the combination of both tests seems to be the best, as the investigators show."

"I'd say the number 1 takeaway is that the most sensitive preoperative exploration for a patient with hyperparathyroidism is some combination of ultrasound scan and sestamibi scan," concluded Dr. Doherty.

Dr. Işik and Dr. Doherty have disclosed no relevant financial relationships.

American Thyroid Association (ATA) 80th Annual Meeting: Abstract 186. Presented September 26, 2009.

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