Abstract
Background
The intraoperative parathyroid hormone (IOPTH) assay is an important tool that facilitates targeted parathyroidectomy and may increase surgical cure rates. We sought to evaluate the utility of a point-of-care assay to distinguish parathyroid adenomas from nonparathyroid tissues, which can sometimes pose a challenge during parathyroidectomy and is commonly achieved with the use of frozen sections. We hypothesized that point-of-care rapid IOPTH assays of needle aspirates from suspected adenomas would be faster and equal in accuracy to frozen sections.
Methods
Parathyroid and nonparathyroid lesions were excised, and the tissues were needle aspirated, diluted in saline, and submitted to a rapid IOPTH assay located in the operating room. Frozen sections were simultaneously sent for analysis. The time intervals to result availability were tracked and compared using a paired t test.
Results
Point-of-care IOPTH assays of needle aspirates were available in a mean (±SD) of 11.6 ± 1.5 minutes compared to 18.7 ± 4.0 minutes for frozen sections ( P = .005). The findings were concordant 100% of the time for both parathyroid (mean parathyroid hormone [PTH] > 3338.9 pg/mL) and parathyroid tissues (mean PTH = 8.7 pg/mL).
Conclusion
Point-of-care IOPTH assay of needle aspirates is an accurate method of distinguishing parathyroid from nonparathyroid tissues. It is suggested that this would be particularly useful in instances where use of IOPTH is planned for assessment of a drop in serum PTH.
1
Introduction
Primary hyperparathyroidism is a common endocrine problem, with approximately 100 000 new cases diagnosed each year in the United States . It is caused by a single adenoma in 87% to 91% of the cases. Less common causes of primary hyperparathyroidism include 4-gland hyperplasia, double adenomas, and, rarely, parathyroid carcinoma .
Parathyroidectomy is the only curative treatment of primary hyperparathyroidism that resolves metabolic complications as well as improves symptoms and quality of life . Over the last decade, there has been an improvement of localizing studies such as technetium Tc 99m–sestamibi scan and high-resolution ultrasound to identify the enlarged, hyperfunctioning parathyroid glands. These technological advances now allow surgeons to perform a minimally invasive, targeted parathyroidectomy, often obviating the need for a traditional 4-gland neck exploration .
In this study, we sought to prospectively evaluate the benefit of an IOPTH assay of needle aspirates obtained from parathyroid and nonparathyroid tissues and processed inside the operating room (point-of-care) to help identify and confirm parathyroid adenomas. We hypothesized that this assay might shorten the operative time while providing the same accuracy as frozen section in confirming parathyroid tissue.
2
Methods
Patients who underwent parathyroidectomy for hyperparathyroidism by the senior author during the months of May and June 2009 were included in this study. Data were collected prospectively. Permission to access protected health information for this purpose was granted by the institutional review board of the Medical College of Georgia.
The parathyroidectomy technique varied depending on preoperative imaging. When either or both the sestamibi scan or ultrasound localized, a minimally invasive, targeted approach was used with or without endoscopic guidance . If the imaging did not localize a single diseased gland, a 4-gland exploration was undertaken. After excision of parathyroid and nonparathyroid tissues, the lesions were aspirated with a 23- to 25-gauge needle attached to a 3-mL syringe using multiple passes. The aspirates were diluted in 3 mL of normal saline and submitted to a point-of-care rapid IOPTH assay (Future Diagnostics, Wijchen, Netherlands). This assay is maintained in the operating room for use in evaluating serum samples for PTH levels during parathyroidectomy . The threshold for identification as nonparathyroid tissue was a value equal to or less than the baseline serum PTH level. An equivocal finding was a value between the serum level and twice the serum level, and anything higher than that was considered indicative of parathyroid tissue. Simultaneously, frozen sections were sent for analysis by a pathologist. In both the minimally invasive and conventional approaches, intraoperative serum PTH levels were sought to determine the sufficiency of the procedure. Time intervals until the results became available to the surgical team were tracked and compared using a paired, 2-tailed t test. All statistical comparisons were made using SPSS for Windows version 14.0 (SPSS Inc, Chicago, IL).
2
Methods
Patients who underwent parathyroidectomy for hyperparathyroidism by the senior author during the months of May and June 2009 were included in this study. Data were collected prospectively. Permission to access protected health information for this purpose was granted by the institutional review board of the Medical College of Georgia.
The parathyroidectomy technique varied depending on preoperative imaging. When either or both the sestamibi scan or ultrasound localized, a minimally invasive, targeted approach was used with or without endoscopic guidance . If the imaging did not localize a single diseased gland, a 4-gland exploration was undertaken. After excision of parathyroid and nonparathyroid tissues, the lesions were aspirated with a 23- to 25-gauge needle attached to a 3-mL syringe using multiple passes. The aspirates were diluted in 3 mL of normal saline and submitted to a point-of-care rapid IOPTH assay (Future Diagnostics, Wijchen, Netherlands). This assay is maintained in the operating room for use in evaluating serum samples for PTH levels during parathyroidectomy . The threshold for identification as nonparathyroid tissue was a value equal to or less than the baseline serum PTH level. An equivocal finding was a value between the serum level and twice the serum level, and anything higher than that was considered indicative of parathyroid tissue. Simultaneously, frozen sections were sent for analysis by a pathologist. In both the minimally invasive and conventional approaches, intraoperative serum PTH levels were sought to determine the sufficiency of the procedure. Time intervals until the results became available to the surgical team were tracked and compared using a paired, 2-tailed t test. All statistical comparisons were made using SPSS for Windows version 14.0 (SPSS Inc, Chicago, IL).
3
Results
Twenty-two parathyroid and nonparathyroid tissues from 14 patients were tested intraoperatively during the study period. Demographic characteristics are reflected in Table 1 . All patients underwent parathyroidectomy for primary hyperparathyroidism with 2 representing reoperative surgery. All patients underwent preoperative technetium Tc 99m–sestamibi scanning, which was localizing in 12 patients (86%). Neck ultrasound was performed in 13 patients and was localizing in 10 (77%). One hundred percent of patients achieved biochemical cure (>50% drop in PTH with a level in the normal range) by termination of surgery.
| Total no. of patients | 14 | |
| Sex | Male, 3; female, 11 | |
| Age (y) | Range | 38–89 |
| Median | 47 | |
| Average | 54.3 | |
| Adenoma weight (mg) | Range | 197–1910 |
| Median | 448 | |
| Average | 884.6 | |
3.1
Frozen section compared to point-of-care IOPTH
A total of 22 tissue samples were analyzed, with 19/22 being submitted for frozen section analysis and needle-washings PTH assay, and 3/22 undergoing PTH assay only (final pathology on these 3 tissues revealed 2 lymph nodes and 1 parathyroid tissue). On frozen section analysis, 17/19 of the tissue samples were confirmed to be parathyroid tissue, and 2/19 were confirmed as nonparathyroid tissue (lymph node and thyroid tissue, respectively). Two of the 14 patients had double adenomas, and one patient had 4-gland hyperplasia. Tissues that proved to be nonparathyroid on either frozen section or permanent pathology (5 total) had aspirate PTH levels ranging from 7.0 to 10.8 pg/mL, with a mean ± SD of 8.7 ± 1.5 pg/mL. The tissues confirmed to be parathyroid (17 total); all yielded PTH levels exceeding the upper limit of the assay, with a mean of 3338.9 ± 714 pg/dL ( Fig. 1 ). The needle-aspirate PTH levels, therefore, correctly predicted the type of tissue in every case (resulting in 100% concordance, with 100% sensitivity and specificity) ( Fig. 2 ).
