Use of a rapid intraoperative parathyroid hormone assay in the surgical management of parathyroid disease

Use of Intraoperative Parathyroid Hormone in Minimally Invasive Parathyroidectomy for Primary Hyperparathyroidism: A Systematic Review and Meta-analysis

Importance

Intraoperative parathyroid hormone (ioPTH) is a surgical adjunct that has been increasingly used during minimally invasive parathyroidectomy (MIP). Despite its growing popularity, to our knowledge a meta-analysis comparing MIP with ioPTH vs MIP without ioPTH has not yet been conducted.

Objective

To evaluate the safety and efficacy of MIP with ioPTH for treatment of primary hyperparathyroidism.

Data Sources

A systematic search of the databases PubMed, Embase, Scopus, Web of Science, and Cochrane Collaboration was performed to identify studies that compared MIP with and without ioPTH. Data were analyzed between August and September 2019.

Study Selection

Inclusion criteria consisted of randomized clinical trials and observational studies with a retrospective/prospective design, comparing MIP using ioPTH vs MIP not using ioPTH for treatment of primary hyperparathyroidism. Eligible studies had to present odds ratio (OR), risk ratio, or hazard ratio estimates (with 95% CI), standard errors, or number of events necessary to calculate these for the outcome of interest rate. Studies involving patients with secondary or tertiary hyperparathyroidism or those with multiple endocrine neoplasia syndrome were excluded.

Data Extraction

Two reviewers independently reviewed the literature according to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guidelines. Dichotomous variables were pooled as ORs while continuous variables were compared using weighted mean differences. Quality assessment was performed using the Newcastle-Ottawa Scale.

Main Outcomes and Measures

The primary outcome was rate of cure. Secondary outcomes included need for reoperation, need for bilateral neck exploration, morbidity, and length of surgery.

Results

A total of 12 studies, involving 2290 patients with primary hyperparathyroidism, were eligible for inclusion. The median (SD) age of participants was 60.1 (11.8) years and 77.3% of participants were women. The median Newcastle-Ottawa score was 7. Patients who underwent MIP with ioPTH had higher cure rates (OR, 3.88; 95% CI, 2.12-7.10; P < .001). There was a greater need for reoperation in the group of patients who had surgery without ioPTH (OR, 0.40; 95% CI, 0.19-0.86; P = .02). There was a trend toward longer operating times/increased duration of surgery in the ioPTH group; however, this did not reach statistical significance (weighted mean difference, 21.62 minutes; 95% CI, -0.93 to 44.17 minutes; P = .06). The use of ioPTH was associated with higher rates of bilateral neck exploration (OR, 3.55; 95% CI, 1.27-9.92; P = .02).

Conclusions and Relevance

Use of ioPTH is associated with higher cure rates for patients with primary hyperparathyroidism undergoing MIP. Minimally invasive parathyroidectomy performed without ioPTH is associated with less conversion to bilateral neck exploration at initial surgery but with lower cure rates and an increased risk for reoperation.

Trial Registration

PROSPERO identifier: CRD42020148588.

SURGERY OUTCOMES IN PATIENTS WITH SECONDARY HYPERPARATHYROIDISM AND IMPACT OF INTRA-OPERATIVE PTH MEASUREMENT

Context

The current therapeutical management of secondary hyperparathyroidism (S-HPTH) is difficult to obtain due to the lack of kidney donors. Surgical intervention on the pathologic parathyroid tissue has been suggested as a method to alleviate symptoms in patients with chronic kidney disease (CKD).

Objective

The aim of our study was to evaluate the outcomes of parathyroid surgery in patients with S-HPTH and the advantages of intraoperative quick PTH (iqPTH) to improve surgical results.

Material and methods

In a real-life study, we compared one group of S-HPTH with iqPTH performed after removing all suspected glands and before wound suture (Group 1) and one group in that iqPTH was not assessed (Group 2). When iqPTH dropped less than 50%, additional exploration followed.

Results

Eight out of the 34 patients from Group 1, who underwent subtotal parathyroidectomy, showed elevated levels of serum PTH and calcium, which remained elevated during follow-up, thus, suggesting disease persistence. From the 21 patients in Group 2, none showed early postoperative disease persistence. Serum calcium, but not PTH was increased in one patient from the iqPTH group but normalized after one month. Overall, iqPTH allowed detection of a supplementary parathyroid gland in one case, thereby increasing early post-surgery remission to 100% in Group 2 compared to 76.47% in Group 1. Late postoperative remission of hyperparathyroidism with no further increase in the rate of hypoparathyroidism was obtained in Group 2.

Conclusions

Assessment of intra-operative PTH levels proved to be a useful tool in augmenting the outcome of S-HPTH surgery. In patients which are eligible for renal transplantation who undergo a subtotal resection, iqPTH can enhance the post-operative quality of life by lowering disease recurrence rates until the kidney transplant procedure.

Validation of selective use of intraoperative PTH monitoring in parathyroidectomy

BACKGROUND

The objective of this study was to validate our approach of treating primary hyperparathyroidism using sestamibi scan directed parathyroidectomy, without routine use of intraoperative parathyroid hormone measurements (ioPTH).

METHODS

We prospectively established a protocol limiting the use of ioPTH to patients with negative or equivocal sestamibi scans, and those who had risk factors for multi-gland disease. We then performed a retrospective review to determine our disease control rate.

RESULTS

128 patients underwent sestamibi-guided parathyroidectomy without (111/128 = 87%) or with (17/128 = 13%) ioPTH. The overall disease control (eucalcemia) rate was 95%. 3/111 (3%) of patients who had surgery without ioPTH measurements required re-exploration.

CONCLUSIONS

Selective use of ioPTH is an effective strategy. ioPTH is best reserved for patients who have non-localizing preoperative imaging, are at risk for multi-gland disease, or require revision surgery.

Postoperative Hypoparathyroidism and the Viability of the Parathyroid Glands During Thyroidectomy

OBJECTIVES

To prevent hypoparathyroidism after thyroidectomy, preservation of the parathyroid glands and their vascularity are essential. The aim of this study was to determine the association between postoperative parathyroid function and the viability of the parathyroid glands during thyroidectomy.

METHODS

We prospectively analyzed 111 patients who underwent total thyroidectomy and in whom all 4 parathyroid glands were preserved in situ during the operation. The surgeons scored the viability of each parathyroid gland from 0 (normal) to 3 (severely compromised viability) based on its gross appearance and vascularity intraoperatively. The index of parathyroid viability score (IPVS) was defined as the sum of the viability scores of the 4 parathyroid glands. We evaluated the relationship between postoperative parathyroid function and IPVS.

RESULTS

Transient hypoparathyroidism occurred in 25 patients (22.5%), and permanent hypoparathyroidism in 4 patients (3.6%). The IPVS were significantly different in the three groups: 2.87±1.46 in the normal group, 3.68±1.41 in the transient hypoparathyroidism group and 7.50±1.00 in the permanent hypoparathyroidism group. The rates of transient hypoparathyroidism were 13.6% in patients with IPVS 0-2, 23.8% in patients with IPVS 3-4, and 42.9% in patients with IPVS 5-6. All the patients with IPVS of 7 or more had permanent hypoparathyroidism.

CONCLUSION

IPVS is correlated with the incidence of hypoparathyroidism. It could be a good quantitative indicator of the probability of hypoparathyroidism after thyroidectomy.

Intra-operative parathyroid hormone kinetics and influencing factors with high baseline PTH: a prospective study

BACKGROUND AND OBJECTIVE

Intra-operative parathyroid hormone (IOPTH) kinetics and therefore the efficacy of IOPTH utilization as a predictor of cure are likely to be affected by baseline IOPTH levels, vitamin D deficiency and parathyroid weight.

PATIENTS AND METHODS

Consecutive subjects with primary hyperparathyroidism (PHPT, n = 51) undergoing parathyroidectomy with IOPTH monitoring were studied prospectively during the period October 2009-November 2011. Samples were collected pre-incision, pre-excision and post-excision (5, 10, 15 min). Iterative analysis of IOPTH kinetics and half-life calculation was carried out in subgroups. Nonparametric testing was used for group statistics.

RESULTS

Hypovitaminosis D (25(OH)D3 < 50 nm) was present in 39 (76%), serum PTH > 1000 ng/l in 23 (45%), and giant parathyroid adenoma (weight > 3000 mg) in 23 (45%). The percentage drop at 10 min was significantly higher in large adenomas (weight > 3000 mg). Miami and 5 min criteria showed the highest negative predictive value and maximum accuracy. The average percentage IOPTH drop observed at 5 min post-excision was 79.8%. Kinetic analysis showed a mean half-life of PTH of 2.57 ± 0.27 min (range: 0.07-11.55).

CONCLUSION

IOPTH monitoring is reliable even in patients with extremely high baseline IOPTH value, with a greater percentage drop at 5 and 10 min post-excision. In patients with high baseline IOPTH, a 50% decay in PTH value at 5 min may be indicative of cure, obviating the need for 10 and 15 min samples. IOPTH kinetics are altered by adenoma weight but not affected by vitamin D status or baseline IOPTH levels.

The value of intraoperative PTH measurements in patients with mild primary hyperparathyroidism

PURPOSE

Intraoperative parathyroid hormone (ioPTH) measurement has facilitated a move to minimally invasive parathyroidectomy. Patients are referred for surgery earlier with milder hypercalcaemia and smaller tumours. Whilst previous research has shown that glands size can affect ioPTH kinetics in patients with multiple gland disease, the dynamics of ioPTH in patients with mild hyperparathyroidism (HPT) has not been studied. We therefore investigated the relationship between biochemical parameters and parathyroid adenoma weight, and determined the dynamics and accuracy of ioPTH assay in patients with milder hypercalcaemia undergoing parathyroidectomy.

METHODS

Patients undergoing parathyroidectomy for single gland disease from January 2004 to March 2011 were divided prospectively into two groups according to preoperative serum calcium: patients with a preoperative calcium ≥ 2.85 mmol/L (11.4 mg/dL) and <2.85 mmol/L were grouped as severe and mild hypercalcaemia, respectively. Correlation coefficients were calculated to assess the relationship between biochemical markers of calcium homeostasis and ioPTH measurements with respect to parathyroid gland weight.

RESULTS

There was a weak correlation of preoperative serum calcium (r = 0.248, r = 0.207), PTH (r = 0.392, r = 0.275), and baseline ioPTH (r = 0.516, r = 0.244) with parathyroid gland weight in severe (n = 113) and mild groups (n = 190), respectively. No correlation between the magnitude in ioPTH drop with parathyroid gland weight at 5 or 10 min post-excision for either group was observed. Success rates (post-operative normocalcaemia) were similar for each group (99.1 % severe, 98.9 % mild).

CONCLUSION

This prospective study provides evidence that ioPTH assay is a valuable tool in predicting adequate tissue removal in patients with milder and more severe hypercalcaemia due to single gland primary HPT.

Directed parathyroid exploration: Evolution and evaluation of this approach in a single-institution review of 346 patients

OBJECTIVES/HYPOTHESIS

Critical evaluation of a directed exploration protocol used by a single surgeon in the management of surgical parathyroid disease.

STUDY DESIGN

Retrospective chart review was made of patients surgically managed for hyperparathyroidism at an academic tertiary care center.

METHODS

Three hundred forty-six patients were evaluated for biochemically proven hyperparathyroidism between March 1995 and February 2002. A directed exploration protocol was implemented in appropriately selected patients with primary hyperparathyroidism and in patients with secondary or tertiary hyperparathyroidism requiring repeat operation. The protocol included preoperative technetium-99m sestamibi imaging for hyperfunctional parathyroid localization, targeted neck exploration, rapid intraoperative parathyroid hormone determination, and limited-stay discharge from the ambulatory surgical recovery unit. Data collection was accomplished by entering patient evaluation, management, and outcome information prospectively into collective case report forms. A retrospective analysis of the data was conducted for the purpose of evaluating the effectiveness of the protocol.

RESULTS

Sustained normocalcemia beyond 6 months postoperatively was achieved in 323 of 327 (99%) patients with primary hyperparathyroidism. Eighty-four percent (84%) of patients with secondary or tertiary hyperparathyroidism achieved normocalcemia or had resolution of symptoms as a measure of therapeutic success. The complication rate for the entire series of patients was 2.8%. Ninety-two percent of positive findings on sestamibi scan correctly predicted the location of an adenoma, whereas a negative finding accurately predicted the absence of an enlarged gland in a "usual" location in 81% of patients. Twenty-six patients (9%) had a false-positive finding on the scan, whereby a solitary adenoma was found contralateral to the side indicated by the scan. Overall, the positive predictive value for sestamibi imaging in the series was 91%. Intraoperative parathyroid hormone determination yielded an overall rate of reduction of 80% from preoperative levels during directed exploration. Sustained normocalcemia was achieved in all patients in whom intraoperative parathyroid hormone determination demonstrated a minimum decline of 50% from preoperative levels following resection of hyperfunctional parathyroid tissue (adenoma[s]). The majority (72%) of patients were managed in an outpatient (ambulatory surgery) setting and were discharged to home within 8 to 12 hours after surgery.

CONCLUSION

The directed exploration protocol for surgical management of hyperparathyroidism generated surgical rates of success that were as good as and, in most cases, improved over that of traditional bilateral exploration. This achievement was associated with low morbidity and reduced time and facility utilization, conveying improved cost-effectiveness. This surgical strategy should serve to enhance the capability of the surgeon to safely and efficiently manage the majority of patients with surgical parathyroid disease.

Long-term outcome of patients with intraoperative parathyroid level remaining above the normal range during parathyroidectomy

BACKGROUND

Criterion requiring intraoperative parathyroid hormone (IOPTH) drops >50% from the highest, preincision or preexcision level, 10 minutes after the abnormal gland's excision predicts operative success with 98% accuracy. The purpose of this study is to correlate IOPTH dynamics with recurrent hyperparathyroidism (RecHPT) and eucalcemia with high PTH (HPTH).

METHODS

We followed 383 consecutive patients with parathyroidectomy guided by IOPTH monitoring using the above criterion for >6 months. Calcium and PTH levels were measured for 50 months (range, 6-173). Patients were divided in 2 groups: group 1 comprised 302 participants with IOPTH levels that decrease to the normal range (NR), and group 2, with 81 participants who had >50% IOPTH decrease but remained above the normal range. The incidence of RecHPT and eucalcemia with HPTH was evaluated.

RESULTS

RecHPT was found in 2% (8/383) of patients and eucalcemia with HPTH was present in 19% (74/383). In group 1, 17% (52/302) had eucalcemia with HPTH, whereas in group 2, this incidence was 27% (22/81; P = .04). However, only 2% of those (6/302) in group 1 and 2.5% (2/81) in group 2 developed RecHPT (P = .76). Conversely, 70.5% of those (57/81) in group 2 were eucalcemic with normal PTH.

CONCLUSION

Although postoperative eucalcemia with HPTH was significantly higher among patients with IOPTH above the normal range than in patients in group 1, the incidence of RecHPT was not increased. The majority of patients in whom IOPTH did not drop to the normal range continue to be biochemically normal after the operation.

QuiCk-IntraOperative Bio-Intact PTH assay at parathyroidectomy for secondary hyperparathyroidism

BACKGROUND

In uremic patients, metabolism of 1-84 parathyroid hormone (PTH) and fragments are delayed, and in these patients, the usefulness of intraoperative PTH assay may be problematic. We evaluated the usefulness of the QuiCk-IntraOperative Bio-Intact PTH (QPTH) assay for uremic patients with secondary hyperparathyroidism who required total parathyroidectomy (PTx) with forearm autograft. The purpose of our study was to recognize whether QPTH in uremic patients was useful to determine during operation whether complete PTx had been achieved.

METHODS

Forty-four patients who underwent initial PTx were enrolled in this study. Blood samples were drawn just after induction of general anesthesia (basal samples), immediately after removal of the last gland, and at 5, 10, 15, and 30 minutes, and at the first morning after PTx. The assay was performed immediately after sample collection. Reductions of PTH levels were evaluated and expressed in percentage of basal levels.

RESULTS

The mean PTH levels in 41 patients, excluding 3 in whom the PTH level did not drop significantly (>60 pg/ml), measured by QPTH at anesthesia, 0, 5, 10, 15, and 30 minutes were 734.3, 104.7, 58.8, 37.4, 27.0, 16.3 pg/ml, corresponding to 100%, 17.1%, 9.3%, 5.8%, 4.1%, 2.4% of the preexcision values, respectively. If the cutoff value was defined as 10.8% at 10 minutes, the sensitivity was 100% and specificity 90%. When the QPTH level dropped to under 10.8% at 10 minutes, we could consider that all glands were removed.

CONCLUSIONS

QPTH in uremic patients is very useful to determine whether complete PTx is achieved during operation.

Parathyroidectomy monitored by intra-operative PTH: The relevance of the 20 min end-point

OBJECTIVES

RI-PTH measurements are a prerequisite for minimally invasive parathyroidectomy, providing guidance regarding the removal of hyper-functioning tissue. Different criteria of PTH decrease, concentration and clearance were analyzed in order to predict surgical treatment.

DESIGN AND METHODS

Blood samples at pre-incision, manipulation, 5, 10 and 20 min after resection, were collected from 145 patients presenting unambiguous, pre-surgical "single adenoma" diagnosis.

RESULTS

The meeting of Irvin criterion would have permitted the identification of 28% uncured cases leading to 4% unnecessary neck exploration. On the contrary, we would have identified all of the uncured patients, to the detriment of 7% unnecessarily prolonged procedure by taking into account PTH drop, concentration and clearance shape at 20 min.

CONCLUSIONS

The 20' end-point plays a key role in the correct determination of surgical outcome, strongly improving the possibility of adequate patient treatment. However, since the high success rate of traditional parathyroidectomy, yet not provided by RI-PTH, the utmost improvement to hyper-parathyroidism surgical treatment by RI-PTH could be achieved in pre-operative equivocal glands localization or multiglandular disease selected population to quickly guide and confirm the complete removal of all hyper-secreting tissue.

Interpretation of intraoperative parathyroid hormone monitoring in patients with baseline parathyroid hormone levels of <100 pg/mL

BACKGROUND

Common guidelines for intraoperative parathyroid hormone (IOPTH) interpretation are based on clearly elevated baseline parathyroid hormone (PTH) values. We hypothesize that patients with low-baseline levels (<100 pg/mL) have a higher incidence of multigland disease (MGD) and display differences in PTH kinetics compared with patients with high-baseline levels.

METHODS

We retrospectively reviewed the cases of 1151 patients with primary hyperparathyroidism who underwent parathyroidectomy with IOPTH monitoring. Of these, 141 patients had low-baseline values. Multiple comparisons were made between the low-baseline and high-baseline groups.

RESULTS

Twenty-six percent of the low-baseline patients had MGD versus 15% of the high-baseline patients (P = .002). The PTH kinetics differed between groups after gland excision at both 5 and 10 minutes. Adherence solely to the "50% rule" during minimally invasive parathyroidectomy potentially would have missed 25% of patients with MGD in the low-baseline group versus 10% in the high-baseline group; 5.7% of the low-baseline patients had persistent or recurrent hypercalcemia versus 2.9% of the high-baseline patients.

CONCLUSION

MGD is significantly more prevalent among low-baseline patients, and PTH kinetics are somewhat different between groups. The current guidelines that are used for IOPTH monitoring may not be ideal for use in this low-baseline group and will likely need to be revised after further study of this group of patients.

The use of rapid parathyroid hormone assay in predicting postoperative hypocalcemia after total or completion thyroidectomy

PURPOSE

To evaluate the rapid parathyroid hormone assay (rPTH) as a perioperative tool in predicting postoperative symptomatic hypocalcemia following thyroidectomy.

METHODS

We conducted a prospective study of 69 patients undergoing total or completion thyroidectomy. Rapid PTH levels were obtained preoperatively, intraoperatively, and postoperatively upon arrival in the postanesthesia care unit (PACU). All patients were closely monitored postoperatively for the development of symptomatic or asymptomatic hypocalcemia.

RESULTS

Of 60 patients (25%) undergoing thyroidectomy, 15 developed hypocalcemia, 7 (11.7%) were symptomatic, and 8 (13.3%) asymptomatic. An intraoperative rPTH level less than 12 pg/mL was 71% sensitive and 95% specific for predicting postoperative symptomatic hypocalcemia, whereas a PACU rPTH level less than 12 pg/mL was 100% sensitive and 92% specific. A greater than 75% decline in preoperative rPTH level when measured intraoperatively was 71% sensitive and 86% specific, whereas a greater than 75% decline in rPTH level in the PACU was 100% sensitive and 88% specific for predicting symptomatic hypocalcemia.

CONCLUSIONS

The rPTH assay is a highly accurate and effective tool for predicting symptomatic hypocalcemia immediately after thyroidectomy. Routine utilization of this assay is recommended, because it will allow safe and timely discharge of normocalcemic patients and the early identification of patients requiring treatment of postthyroidectomy hypocalcemia.

The role of intraoperative parathyroid hormone testing in patients with tertiary hyperparathyroidism after renal transplantation

BACKGROUND

Intraoperative parathyroid hormone (PTH) testing has been shown to accurately define adequacy of parathyroid resection in patients with primary hyperparathyroidism (HPT) and alters the operative management in 10% to 15% of cases. However, the benefit of this technique in patients with tertiary HPT after renal transplantation undergoing parathyroidectomy is unclear.

METHODS

Intraoperative PTH was measured in 32 consecutive patients undergoing parathyroidectomy for tertiary HPT after renal transplantation between March 2001 and November 2004 by using the Elecsys assay at baseline and, subsequently, 5, 10, and 15 minutes after curative resection. The outcomes of these patients were evaluated.

RESULTS

All patients were cured after surgery. Of the 32 patients, 29 were found to have parathyroid hyperplasia, while 1 had a single adenoma and 2 had double adenomas. The average drop in intraoperative PTH levels after curative resection was 69 +/- 3.5% at 5 min., 77 +/- 2.3% at 10 minutes, and 83 +/- 3.4% at 15 minutes. PTH testing changed the intraoperative management in 5 (16%) patients. One patient with a single adenoma and 2 patients with double adenomas had a >50% drop at 10 minutes. after excision; therefore, the operation was terminated without further resection. Two patients did not have a >50% drop at 10 minutes after 3.5 gland resection. These patients were explored further, and additional supernumerary parathyroid glands were identified and resected. After resection of these additional glands, the PTH fell by >50%, indicating cure.

CONCLUSIONS

In patients undergoing parathyroidectomy for tertiary HPT after renal transplantation, a decrease in intraoperative PTH levels >50% at 10 minutes after completion of the operation indicated adequate resection. Furthermore, intraoperative PTH testing altered the operative management in 16% of patients. Therefore, similar to its role in patients with primary HPT, intraoperative PTH testing appears to play an equally important role in the management of patients with tertiary HPT undergoing parathyroidectomy.

A systematic review of the diagnosis and treatment of primary hyperparathyroidism from 1995 to 2003

OBJECTIVE

To systematically review the current preoperative diagnostic modalities, surgical treatments, and glandular pathologies associated with primary hyperparathyroidism.

STUDY DESIGN

A systematic literature review.

RESULTS

Of the 20,225 cases of primary hyperparathyroidism reported, solitary adenomas (SA), multiple gland hyperplasia disease (MGHD), double adenomas (DA), and parathyroid carcinomas (CAR) occurred in 88.90%, 5.74%, 4.14%, and 0.74% of cases respectively. Tc 99m -sestamibi and ultrasound were 88.44% and 78.55% sensitive, respectively, for SA, 44.46% and 34.86% for MGHD, and 29.95% and 16.20% for DA, respectively. Postoperative normocalcemia was achieved in 96.66%, 95.25%, and 97.69% of patients offered minimally invasive radio-guided parathyroidectomy (MIRP), unilateral, and bilateral neck exploration (BNE). Intraoperative PTH assays (IOPTH) were helpful in approximately 60% of bilateral neck exploration conversion (BNEC) surgeries.

CONCLUSION

The overall prevalence of multiple gland disease (MGD and DA) was lower than often suggested by conventional wisdom. Furthermore, preoperative imaging was less accurate than it is often perceived for accurately imaging MGD. MIRP and UNE were more successful in achieving normocalcemia than is typically quoted. IOPTH was a helpful but not "fool-proof" adjunct in parathyroid exploration surgery.

SIGNIFICANCE

These results support a greater role for the treatment of primary hyperparathyroidism using less invasive approaches. EMB rating: B-3.

Intraoperative rapid parathyroid hormone monitoring in parathyroid surgery

The approach to parathyroid surgery has changed from bilateral exploration to focused, minimally invasive surgery. The intraoperative rapid parathyroid hormone assay has become an important tool in modern parathyroid surgery. This article outlines the technique and interpretation of the assay. Results of studies that evaluate the validity of the technique are summarized. The limitations and pitfalls of this technique are also discussed.

Intraoperative testing for parathyroid hormone: a comprehensive review of the use of the assay and the relevant literature

OBJECTIVE

The rapid intraoperative parathyroid hormone assay is transforming the parathyroidectomy procedure. We present a review of the literature on the use of the assay as an adjunct to surgery. To our knowledge, this is the first review of the literature to encompass and compare all known primary studies of this assay in parathyroidectomy patients.

DATA SOURCES

Articles were collected by searching MEDLINE databases using relevant terminology. The references of these articles were reviewed for additional studies. Supplementary articles pertinent to the parathyroidectomy procedure, preoperative parathyroid localization studies, and intraoperative parathyroid hormone assay development also were examined.

STUDY SELECTION AND DATA EXTRACTION

One hundred sixty-five references were analyzed and categorized separately into groups.

DATA SYNTHESIS

The primary studies of intraoperative data on patients undergoing parathyroidectomy were compared when possible. Studies were analyzed by type of assay used, where performed, turnaround time, and efficiency of use. Reviews of the types of parathyroid surgery and preoperative localization were included for educational purposes.Conclusions.-The intraoperative parathyroid hormone assay is a useful adjunct to preoperative imaging and parathyroid surgery because of its unique ability to detect an occult residuum of hyperfunctioning parathyroid tissue. Use of this assay will obviate the need for frozen section in most routine cases. The test facilitates minimally invasive parathyroidectomy for single parathyroid adenomas, which, in turn, improves cost-effectiveness and cosmetic outcome. Its use in patients with known preoperative multiglandular disease is promising but requires further study.

Surgical considerations and controversies in thyroid and parathyroid surgery

The techniques of thyroid surgery have been fully elucidated in several surgical texts and atlases. This article discuss surgical pearls of thyroid and parathyroid surgery. We discuss preoperative, intraoperative, and postoperative considerations and controversies for both procedures.

Surgical management of the parathyroids

The recent advance of intraoperative PTH monitoring combined with preoperative localization techniques allow for minimally invasive parathyroid surgery in 75% to 85% of cases. In cases where a single adenoma is identified, minimally invasive techniques should result in a need for repeat surgery in only 2% of cases. The cost of intraoperative PTH assays of localization and gamma probes limits their availability. Complications of parathyroidectomy are uncommon, but appropriate management is important, particularly for patients with hypocalcemia.

Kinetic Analyses of Parathyroid Hormone Clearance as Measured by Three Rapid Immunoassays during Parathyroidectomy

Background: Rapid intraoperative parathyroid hormone (PTH) measurements are an important prerequisite for minimally invasive parathyroidectomy, serving as a feasible marker for “cure” because of the short half-life of PTH. Because automated analysis may facilitate monitoring, two automated PTH assays were compared with an established manual method.

Methods: We collected 109 plasma samples during minimally invasive surgery on 20 patients with primary hyperparathyroidism and single-gland disease. PTH was analyzed manually with a test from Nichols and by two automated assays from Diagnostic Product Corporation (DPC) and Roche, respectively. PTH half-life and residual concentrations were calculated by two kinetic models.

Results: Despite good overall correlations between methods [DPC = 1.07(Nichols) − 12 ng/L; r = 0.95, Sy|x = 26 ng/L and Roche = 1.16(Nichols) − 2.82 ng/L; r = 0.98; Sy|x = 16 ng/L], marked interindividual differences were observed. The iterative kinetic model failed with a nonuniform PTH decrease, but the interpolative model produced valid results. The mean (SD) half-life of 3.7 ± 1.4 min with DPC differed significantly (P &lt;0.05) from the 4.3 ± 1.6 min with Roche (Nichols, 4.0 ± 1.6 min). DPC produced significantly lower mean residual PTH (15 ng/L) vs Roche (27 ng/L); Nichols results were between them (20 ng/L). However, these differences were clinically irrelevant.

Conclusions: Automated methods are as suitable as the manual test. The preoperative baseline PTH is necessary but is insufficient for kinetic calculations.

Intraoperative parathyroid hormone testing: survey of testing program characteristics

OBJECTIVE

To examine the number and testing characteristics of laboratories that offer intraoperative testing of intact parathyroid hormone (PTH).

DESIGN

Laboratories (n = 355) that participated in 2001 in PTH proficiency testing with the College of American Pathologists Special Ligand Survey were surveyed about intraoperative PTH testing.

RESULTS

Of the 320 laboratories that responded to the survey, 92 performed intraoperative PTH testing. Testing practices were divided nearly equally among laboratories that performed intraoperative PTH testing for all parathyroidectomies (40%), most but not all cases (31%), and less than half of cases (30%). Testing frequency usually was low, with about two thirds of laboratories reporting 5 or fewer cases per month. A surprising finding was that, although intraoperative PTH testing originally became widely practiced as a point-of-care test, 71% of laboratories performed testing in a central laboratory, 6% in satellite laboratories, and only 23% in operating suites. A survey of methods showed that 33% used the manual QuiCk-Intraoperative test, 47% used the automated Immulite Turbo intact PTH assay, and 20% used other methods.

CONCLUSIONS

Intraoperative testing of intact PTH, although relatively new, has come into widespread practice during parathyroid surgery. Service delivery has evolved from a point-of-care model toward a central laboratory model, with this test serving as an illustrative example of factors that affect the balance between point-of-care and laboratory testing.

Evaluation of the Performance and Clinical Impact of a Rapid Intraoperative Parathyroid Hormone Assay in Conjunction with Preoperative Imaging and Concise Parathyroidectomy

Background: 99mTc-sestamibi scans and rapid, intraoperative intact parathyroid hormone (PTH) assays allow preoperative identification of diseased glands and intraoperative confirmation of diseased gland removal, respectively. Use of these two new technologies may facilitate simpler, more concise surgery, shorter hospital stays, and decreased costs for frozen-section analysis. One major drawback to this new strategy has been the high cost of rapid point-of-care PTH assays.

Methods: We performed rapid PTH assays with the DPC Turbo PTH assay on the DPC IMMULITE automated analyzer. The number of intraoperative frozen sections, type of anesthesia, surgical approach, length of hospital stay, and pre- and postoperative calcium values were compared between a group of 49 patients undergoing parathyroidectomy where the intraoperative PTH assay was used in conjunction with preoperative imaging, and a historical control group of 55 patients before the use of these two technologies in our institution.

Results: Comparison of the Turbo PTH assay to the standard IMMULITE PTH assay gave the following: y = 1.08x − 4.36 (r = 0.97; n = 48). For the 49 patients, the median turnaround time for each intraoperative PTH determination was 19 min (range, 14–40 min). The median decrease in PTH values from baseline was 88% (range, 33–99%). Thirty-seven patients required two PTH determinations, 7 required three, 4 had four, and 1 required five determinations. The average laboratory cost for the rapid intraoperative PTH assays was &lt;$100 per patient (range, $55 to $113). Compared with the control group, the experimental group had significantly fewer frozen sections (1.4 vs 2.5; P &lt;0.0001), shorter hospital stays (17 discharged on the day of surgery vs none discharged on the day of surgery; P &lt;0.0001), greater use of local anesthesia (33% vs 0%; P &lt;0.001), and more unilateral, rather than bilateral neck explorations (65% vs 0%; P &lt;0.001).

Conclusions: The combination of intraoperative Turbo PTH assay and preoperative 99mTc-sestamibi scans can lead to significant decreases in laboratory and surgical pathology costs, hospital stays, and exposure to general anesthesia by facilitating concise parathyroidectomy surgery.

Intraoperative Parathyroid Hormone Analysis: A Study of 200 Consecutive Cases

Background: Immunoassays for parathyroid hormone (PTH), with short incubation times and results available in &lt;15 min, have allowed intraoperative monitoring of the success of parathyroid surgery. The purpose of this study was to evaluate the analytical performance of a rapid PTH assay and its clinical performance in a series of 200 patients.

Methods: PTH was measured with a modified immunochemiluminometric assay with a 7-min incubation time (QuiCk-IntraOperative™ Intact PTH assay). The rapid assay was compared with results in a central laboratory (immunoradiometric assay) in 44 EDTA-plasma specimens. The rapid assay was used intraoperatively in 200 consecutive cases with specimens analyzed before and 5–10 min after resection of the hypersecreting parathyroid gland(s).

Results: Intraassay imprecision was 12% at 28 ng/L and 11% at 278 ng/L. Regression analysis of results of the rapid PTH assay and the IRMA PTH assay in 44 parathyroidectomy patients yielded y = 1.26x − 12 ng/L, Sy|x = 26.3 ng/L, r = 0.984, and in 40 of 44 patients with values &lt;200 ng/L, y = 1.02x + 1.9, Sy|x = 13.9, r = 0.947. In the 195 cases using intraoperative PTH testing with complete results and defined clinical outcomes, the overall accuracy of the assay in predicting surgical success was 88% using the criterion of a 50% decrease at 5–10 min and 97% including the subset of patients with delayed decreases of PTH.

Conclusions: The rapid PTH assay had excellent analytical performance and excellent agreement with the PTH immunoradiometric assay and predicted the success of parathyroid surgery in this large series of consecutive patients.

Initial experience with intraoperative PTH determinations in the surgical management of 130 consecutive cases of primary hyperparathyroidism

BACKGROUND

Successful surgical management of primary hyperparathyroidism (1 degree HPT) historically has required bilateral neck exploration. The intraoperative parathyroid hormone (IO-PTH) assay allows a more limited procedure by confirming complete removal of hypersecreting tissue.

METHODS

Plasma samples were obtained from 130 consecutive patients both before (preincision and preexcision baselines) and at approximately 5 and 10 minutes (and additional times) after removal of abnormal parathyroid tissue. Samples were assayed for IO-PTH by a rapid, two-site immunochemiluminescent assay (ICMA) with a 7-minute incubation at 45 degrees C.

RESULTS

Plasma IO-PTH decreased by at least 50% in 126 of 130 cases; however, three of these cases were false positives. The four cases in which IO-PTH fell < 50% were classified as two true negatives and two false negatives. A single adenoma was removed in 125 cases, and two or three hyperplastic glands were removed in five cases.

CONCLUSIONS

IO-PTH predicted the postoperative outcome in 125 of 130 cases (96.2%), including two of five cases in which multiple hyperplastic glands were removed, and 1 degree HPT was successfully treated in 97.7% (127/130) of the cases. The IO-PTH procedure can provide valuable confirmation to the endocrine surgeon; however, other sources of information must also be used to ensure that all hyperplastic glands are identified.

Kinetic analysis of the rapid intraoperative parathyroid hormone assay in patients during operation for hyperparathyroidism

BACKGROUND

Rapid intraoperative parathyroid hormone (RI-PTH) assay is used to guide adequacy of resection during operation for hyperparathyroidism. We compared the RI-PTH assay (15 minutes) with a standard PTH assay, determined whether the PTH half-life varied between patients, and constructed a kinetic analysis of the RI-PTH data.

METHODS

Forty-five patients with hyperparathyroidism had blood sampled at baseline and at times after parathyroid resection. Intact PTH was determined using RI-PTH and a standard assay. Values were fitted to an exponential decay curve using the baseline and the follow-up time points. PTH half-life and the new postexcision baseline value were calculated from the decay curve.

RESULTS

The RI-PTH assay and the standard PTH assay correlated well. Average PTH half-life was 1.68 +/- 0.94 minutes (0.42 to 3.81 minutes). A kinetic analysis yielded a formula for the generation of a PTH decay curve. Using a 50% reduction in RI-PTH at 5 minutes as the criterion for adequate resection, 2 patients were incorrectly classified as not being cured. These patients were correctly classified using the kinetic analysis.

CONCLUSIONS

PTH half-life can vary substantially. A kinetic analysis may be more accurate in assessing adequacy of resection. This method allows the surgeon to interpret RI-PTH data independent of the timing of samples.