Rapid intraoperative immunoassay of parathyroid hormone and other hormones: a new paradigm for point-of-care testing

Intraoperative Parathyroid Hormone Monitoring Criteria in Primary Hyperparathyroidism: A Network Meta-Analysis of Diagnostic Test Accuracy

Importance

Intraoperative parathyroid hormone (IOPTH) monitoring is recommended by the American Association of Endocrine Surgeons for use during parathyroidectomy for patients with primary hyperparathyroidism (PHPT), but there is no clinician consensus regarding the IOPTH monitoring criteria that optimize diagnostic accuracy.

Objective

To evaluate and rank the diagnostic properties of IOPTH monitoring criteria used during surgery for patients with PHPT.

Data Sources

A bayesian diagnostic test accuracy network meta-analysis (DTA-NMA) was performed, in which peer-reviewed citations from January 1, 1990, to July 22, 2023, were searched for in MEDLINE, Embase, Web of Science, CENTRAL, and CINAHL.

Study Selection

All full-text study designs that evaluated any IOPTH monitoring criteria as a diagnostic test were included in this meta-analysis. Any studies evaluating adult patients diagnosed with PHPT undergoing parathyroidectomy were also included. The reference standard used in this study was normalization of calcium and/or parathyroid hormone levels within 1 year of surgery.

Data Extraction and Synthesis

This DTA-NMA was reported in accordance with the applicable Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guidelines. Two reviewers evaluated all abstracts and full-text articles using a piloted extraction form. A third author resolved any conflicts. There are no published Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) resources for DTA-NMA. The following conventional monitoring criteria were included: Halle, Miami, Rome, Vienna, and PTH normalization, and the following modified criteria were included: Miami and PTH normalization, modified Miami, and modified Vienna. A bayesian hierarchical DTA-NMA model with corresponding 95% credible intervals (CrIs) was used to describe the pooled diagnostic characteristics of the evaluated IOPTH monitoring criteria.

Main Outcomes and Measures

Main outcomes included pooled diagnostic test properties, including sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio.

Results

A total of 72 studies, which included 19 072 patients, met the inclusion criteria. Sixty-nine studies (95.8%) investigated classic PHPT. In PHPT, the Miami criteria were investigated most often and had the best diagnostic properties (diagnostic odds ratio, 60.00 [95% CrI, 32.00-145.00]) when compared to other conventional criteria. Moreover, the modified Miami criteria, which measures a postexcision IOPTH level 15 minutes or more postexcision of all hyperfunctioning parathyroid tissue, were the overall best criteria (diagnostic odds ratio, 79.71 [95% CrI, 22.46-816.67]). There was a low risk of study bias and no publication bias.

Conclusions and Relevance

The results of this meta-analysis suggest that surgeons should use the modified Miami criteria when performing IOPTH-guided surgery for patients with PHPT because these criteria optimize intraoperative diagnostic accuracy by minimizing unnecessary neck exploration and revision surgery rates.

Association of Implementation of Operating Room-Based Parathyroid Hormone Testing with Operative Time and Cost

BACKGROUND

Intraoperative parathyroid hormone (IOPTH) testing facilitates focused parathyroidectomy to establish biochemical cure but may be time-consuming. A dedicated immunoassay machine was relocated to the operating room for IOPTH. These data seek to determine association of operating room-based IOPTH with operative time, laboratory turnaround time (TAT), and cost.

METHODS

Patients who underwent parathyroidectomy from June 2017 to February 2020 were reviewed. Clinical and demographic data, operative time, and TAT were collected. Patients were compared by operation dates pre- or post-machine acquisition. A cost model was created to evaluate cost of care before and after operating room-based testing.

RESULTS

A total of 285 patients were included. Post-machine, median operative time decreased from 69 minutes (interquartile range [IQR] 60 to 84) to 57 minutes (IQR 50 to 84.5), p 0.03. Additionally, median TAT for IOPTH values (preoperative, 0, 5, 10, and 15 minutes) decreased post-machine: time preoperative, 29 minutes (IQR 23 to 40) vs 18 minutes (IQR 17 to 23.5), p < 0.001; time 0, 33 minutes (IQR 27 to 39) vs 18.5 minutes (17.5 to 21), p < 0.001; time 5 minutes, 31 minutes (IQR 26 to 36) vs 20 minutes (IQR 18.5 to 21), p < 0.001; time 10 minutes, 32 minutes (IQR 27 to 39) vs 20 minutes (IQR 18.5 to 22.5), p < 0.001; and time 15 minutes, 30 minutes (IQR 26 to 36) vs 19 minutes (IQR 17 to 21), p < 0.001. Total costs pre- and post-machine were $4,442 and $4,111, respectively. With $331 cost reduction per operation and 127 operations per year, the IOPTH machine pays for itself in 3 years, or 378 surgeries, and saves $168,589 in the machine's remaining 4-year life span.

CONCLUSIONS

Operating room-based parathyroid hormone testing results in improved operating productivity by decreasing result TAT and operative time and reduces cost.

PTH Spikes During Surgical Treatment for Secondary and Tertiary Hyperparathyroidism: A Prospective Observational Study

BACKGROUND

The aim of the present study was to determine whether PTH spikes in renal hyperparathyroidism can interfere with the interpretation of intraoperative PTH monitoring and to determine its frequency and characteristics.

METHODS

This was a prospective observational study of consecutive patients who underwent surgical treatment in a single tertiary institution. Patients were divided into two groups: spike and no spike. Patients with secondary and tertiary hyperparathyroidism were analyzed separately. Intraoperative PTH monitoring by venous serial samples: two samples were taken before the excision of the parathyroid gland, and two others were taken after resection.

RESULTS

PTH spikes occurred in 23.5% (53 of 226), and their occurrence was similar between secondary and tertiary hyperparathyroidism patients (p = 0.074). The relative PTH spike intensity was higher in transplanted patients than in dialysis patients (55 vs. 20%, p = 0.029). A characteristic of the secondary hyperparathyroidism patients was the highest frequency of surgical failure (23 vs. 7.5%, p = 0.016) and the higher occurrence of supernumerary glands in the spike group (23 vs. 10.3%, p = 0.035). Supernumerary parathyroid was associated with surgical failure [19.1 (6.5-55.7) odds ratio [confidence interval], p < 0.001). In the studies evaluating the diagnostic test validity for patients on dialysis and experiencing spikes, the most significant impacts were in the sensitivity, accuracy, and negative predictive value of the method.

CONCLUSIONS

PTH spikes occurred in up to 23.5% of renal hyperparathyroidism surgical treatments and can negatively influence the intraoperative parathyroid hormone monitoring. Regarding the phenomenon of PTH spikes, it is prudent to think about the possibility of a hyperplastic supernumerary gland.

Development, optimization and validation of modified QuEChERS based UPLC-MS/MS for simultaneous determination of nine steroid hormones in milk powder and milk

The simultaneous detection of six estrogens (E1, E2, E3, EE, DES, HEX), two glucocorticoids (DXMS, HC), and 17α-hydoxyprogesterone (OHP).

Multiple Endocrine Neoplasia Type 1 Syndrome: A Case Report and Review of Literature

Multiple endocrine neoplasia type 1 (MEN1) or Wermer’s syndrome is a genetic disease characterized by involvement of multiple endocrine glands, primarily involving parathyroid, pancreas, and pituitary. Other additional features include foregut carcinoids; non-functioning adrenal tumors; and skin lesions such as lipomas, collagenomas, and angiofibromas. Here, we describe our experience in managing a patient who presented to us with spontaneous episodes of hypoglycemia and was diagnosed with insulinoma. Detailed clinical and biochemical evaluation unraveled the diagnosis of MEN1 in the patient and her family members who constituted a large kindred. This case highlights the importance for evaluation of MEN1 in a patient or his/her family members in the setting of clinical and biochemical suspicion. In addition, we have also discussed the utility of the latest diagnostic and therapeutic modalities for management of MEN1.

Data on length of parathyroidectomy surgery and intraoperative parathyroid hormone (PTH) assay turnaround times following a switch in the location for intraoperative PTH testing from near point-of-care to central laboratory

Intraoperative monitoring of parathyroid hormone (PTH) is commonly used during parathyroidectomies. There are a number of practical challenges in achieving rapid turnaround time (TAT) for intraoperative PTH testing, whether the testing is performed point-of-care, near point-of-care, or in a central clinical laboratory. In the related research article, we analyzed a decade of data from 3025 intraoperative PTH tests on 897 unique patients. Of these, 1787 tests on 514 unique patients (375 female, 139 male) occurred while intraoperative PTH measurement was done as near point-of-care testing; the remaining 1238 tests on 383 unique patients (282 female, 101 male) occurred after a switch to intraoperative PTH measurement by the hospital central laboratory. The data in this article provides the patient age, gender, location of surgery (main operating rooms vs. ambulatory surgery center), incision to close time for surgery, and operation start to end times. For the central laboratory testing, additional data are provided for the intraoperative PTH TAT. The analyzed data is provided in the supplementary tables included in this article. Plots of operation start and end times are also included. The dataset reported is related to the research article entitled "Evaluation of Switch from Satellite Laboratory to Central Laboratory for Testing of Intraoperative Parathyroid Hormone" [D. Jacob, G. Lal, D.R. Voss, T. Bebber, S.R. David, J. Kulhavy, S.L. Sugg, A.E. Merrill, M.D. Krasowski, Evaluation of Switch from Satellite Laboratory to Central Laboratory for Testing of Intraoperative Parathyroid Hormone, Pract. Lab. Med. (2020) 22: e00176] [1].

Evaluation of switch from satellite laboratory to central laboratory for testing of intraoperative parathyroid hormone

Objectives

The aim of this study was to evaluate testing turnaround time (TAT) and incision to close time in parathyroid surgeries before and after switching intraoperative parathyroid hormone (PTH) testing from a near point of care location to a central clinical laboratory.

Design and Methods

This retrospective study covered a ten-year period. Both testing locations used the same Roche Diagnostics PTH immunoassay but on different analyzers. The predominant site for surgeries was the main operating rooms (ORs) in an adjacent building, with a limited number of parathyroid surgeries performed at a more distant ambulatory surgery center (ASC). Under ideal conditions, TAT for near point-of-care testing was 20 ​min, although multiple factors could increase TAT. Incision to close time from the electronic health record was used to define time of surgery.

Results

A total of 897 unique patients were identified for which 3031 orders for intraoperative PTH were placed (383 unique patients and 1244 orders after switch in testing site). The average total TAT times for testing (mean ​± ​SD) in the central laboratory were 23.9 ​± ​16.0 ​min (median, 22 ​min) for all specimens, 22.8 ​± ​7.9 ​min (median, 21 ​min) for main OR specimens, and 26.4 ​± ​7.1 ​min (median, 25 ​min) for ASC specimens. Incision to close time for parathyroidectomies showed decreases in mean, median, and standard deviation following testing change.

Conclusions

Surgery time for parathyroidectomies may remain consistent or decrease if intraoperative PTH testing is moved from a near point of care to a central laboratory.

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Turnaround around time for intraoperative parathyroid hormone (PTH) analysis in a central laboratory was evaluated.

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Surgery incision to close times were compared to 514 surgeries with intraoperative PTH performed as near point of care.

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Pre-analytical factors, especially transport time, were the major variable impacting turnaround time.

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The mean, median, and standard deviation for surgery incision to close times decreased in the switch to the central laboratory.

Prediction of post-idroidectomy hypocalcemia through rapid PTH determination

INTRODUCTION

Hypocalcemia is the most frequent complication after thyroidectomy. The aim of this work is to identify biochemical risk factors of hypocalcemia using quick perioperative (pre and post-thyroidectomy) intact parathyroid hormone (PTHi) and postoperative calcemias.

METHODS

In a consecutive series of 310 total thyroidectomies, samples of quick PTHi at the anaesthetic induction and 10 minutes after surgery, together with serum calcemias every 12 hours were obtained. The sensitivity, specificity, positive and negative predictive value are analyzed and related to hypocalcemia. A control group of hemithyroidectomies is also analyzed to compare the effects of surgery on PTH secretion.

RESULTS

Of the 310 patients, 202 (65.1%) remained normocalcemic and asymptomatic (group A), 108 (34.9%) presented hypocalcemia (Group B), requiring oral calcium (79 symptomatic). After analysis of several cut-off points, combining a PTHr drop gradient of 60% or calcemia inferior to 7.4 mg/dl at 24 hours, a sensitivity of 100% is achieved without leaving false negatives. Compared to the control group, there is a significant difference with respect to the post-operative calcemias and PTHr, p < 0.001.

CONCLUSIONS

Total thyroidectomy affects parathyroid function with evident decrease in rPTH and risk of hypocalcemia. The combination of PTHr decrease of 60% or less than 7.4 mg/dl calcemia at 24 hours gives a 100% sensitivity for predicting patients at risk of hypocalcemia.

Indocyanine Green Fluorescence Angiography Can Guide Intraoperative Localization During Parathyroid Surgery

BACKGROUND AND AIMS

Intraoperative localization of pathologic parathyroid glands is of major importance for the hyperparathyroidism treatment. Based on the small size and the anatomic variability, the localization can be very challenging. The current practice is to compare preoperative ultrasonography with Technetium-99m sestamibi scintigraphy (MIBI) and plan the resection accordingly. In this study, we implemented indocyanine green angiography for the intraoperative localization of parathyroid glands.

MATERIALS AND METHODS

This is a retrospective analysis of 37 patients with primary, secondary, or tertiary hyperparathyroidism who were operated using indocyanine green angiography for the intraoperative localization of pathological parathyroid glands. An indocyanine green solution of 2.5 mg was were intravenously administered for parathyroid gland visualization. Different fluorescence scores were correlated with changes in postoperative parathyroid hormone levels.

RESULTS

Patients were divided into two groups depending on the presence of uniglandular or multiglandular disease. Sixty-four lesions were resected, and the final histopathologic analysis confirmed the parathyroid origin in 62 of them (96.8%). None of the patients with uniglandular disease developed postoperative hypoparathyroidism, whereas three patients in the multiglandular group developed temporary hypoparathyroidism symptoms. Indocyanine green imaging had higher sensitivity for the intraoperative detection of parathyroid glands compared with ultrasonography and MIBI (p < 0.001).

CONCLUSION

Indocyanine green angiography indicated high sensitivity for the intraoperative identification of pathologic parathyroid glands leading to a resection rate of 95.16%. The modality was useful, especially in cases of revisional surgery or ectopic parathyroid glands. Randomized trials have already proven the value of indocyanine green imaging in predicting postoperative hypocalcemia. Our results support the regular use of this method during parathyroid surgery.

Focused Parathyroidectomy Using Accurate Preoperative Imaging and Intraoperative PTH: Tertiary Care Experience

INTRODUCTION

The cure rate after focused parathyroidectomy (FP) is dependent upon two critical adjuncts- concordant preoperative imaging and intraoperative parathyroid hormone (PTH), a technique which can reliably determine whether any other hyperfunctioning gland or glands are still present after resection of the lesion shown by imaging. We wanted to see the cure rate of FP by using these two adjuncts. We also sought to discern whether utilizing the central lab rapid PTH assay will lead to wider acceptance of this FP with intraoperative PTH in resource-constrained countries. This analysis was also undertaken to find out cost-effective way of doing intraoperative PTH by minimizing the samples for intraoperative PTH study.

RESULT

Data were collected on 83 patients with sporadic primary hyperparathyroidism (PHPT) who underwent parathyroidectomy in two tertiary centers between '2009 and 2017'. A total of 75 patients had concordant imaging, while seven had discordant imaging. The sensitivity and specificity of intraoperative PTH in FP was 100%. All the 78 patients who had fall in intraoperative PTH (50%) at 10 min also had fall of more than 50% at 5 min except one patient (98.7%).

CONCLUSION

We strongly advocate routine use of intraoperative PTH in all patients undergoing minimally invasive parathyroidectomy, as this adjunct offers maximum safety for the patient and confidence for the surgeon. Cost can be minimized by utilizing the central laboratory and reducing the number of samples.

Rapid electrochemical device for single-drop point-of-use screening of parathyroid hormone

Aim: Novel electrochemical point-of-use biosensing device for rapid assessment of parathyroid hormone (PTH) levels has been developed. Materials & methods: The analytical nanobiosensor was designed by integrating unique high density semiconducting nanostructured arrays on a flexible sensing surface. Surface modification technique was tailored for enhancing the interaction of nanostructure–biological interface to capture the target PTH level. Results & conclusion: We demonstrate a rapid nanobiosensor to detect PTH in human serum, plasma and whole blood with a limit of detection of 1 pg/ml and a clinically relevant dynamic range from 1 to 1000 pg/ml. This is the first demonstration of detecting PTH as a point-of-use device devoid of sample pretreatment suitable in a surgical setting with high specificity to PTH.

Intraoperative Parathyroid Hormone Monitoring in Guiding Adequate Parathyroidectomy

BACKGROUND

Parathyroidectomy has been traditionally performed through bilateral neck exploration (BNE). However, with the use of intraoperative parathyroid hormone (IOPTH) assay along with preoperative localization studies, focused parathyroidectomy can be performed with good surgical success rate, multiglandular disease can be predicted, and hence recurrence and surgical failure can be prevented. Furthermore, it predicts eucalcemia in the postoperative period. The aim of this study was to evaluate the usefulness of IOPTH assay in guiding adequate parathyroidectomy in patients of primary hyperparathyroidism.

MATERIALS AND METHODS

Between year 2015 and 2017, 45 patients of primary hyperparathyroidism underwent parathyroidectomy with IOPTH assay employed as an intraoperative tool to guide the surgical procedure. Blood samples were collected: (1) at preincision time, (2) preexcision of gland, (3) 5-min postexcision of gland, and (4) 10-min postexcision of gland. On the basis of the Irvin criterion, an intraoperative PTH drop >50% from the highest either preincision or preexcision level after parathyroid excision was considered a surgical success. Otherwise, BNE was performed and search for other parathyroid glands done.

RESULTS

Ten-min postexcision PTH levels dropped >50% in 34 (75.6%) patients. True positive among them were 31 (68.8%), true negative 8 (17.7%), false positive 3 (6.6%), and false negative 3 (6.6%). We performed focused exploration at the outset in 40 (88.9%) patients and bilateral exploration for five patients as guided by preoperative localizing studies. Hence, IOPTH was helpful in guiding further exploration in 8 (17.7%) patients and prevented further exploration in 32 (71.1%) patients and also was able to predict eucalcemia in 97.7% patients at 6 months. Thus, IOPTH was able to obviate or to ask for additional procedure in 88.8% of patients. However, in three (6.6%) patients, IOPTH would guide unnecessary exploration and in equally, that is, three (6.6%) patients may require reoperation for unidentified parathyroids.

CONCLUSION

IOPTH in adjunct with other localizing studies is very helpful for carrying out successful parathyroidectomy in uniglandular disease and predicting postoperative eucalcemia. However, more importantly, its role is valuable in equivocal imaging, in such cases, it prevents unnecessary exploration or helps in adequate parathyroidectomy.

Niche point-of-care endocrine testing - Reviews of intraoperative parathyroid hormone and cortisol monitoring

Point-of-care (POC) testing, which provides quick test results in near-patient settings with easy-to-use devices, has grown continually in recent decades. Among near-patient and on-site tests, rapid intraoperative and intra-procedural assays are used to quickly deliver critical information and thereby improve patient outcomes. Rapid intraoperative parathyroid hormone (ioPTH) monitoring measures postoperative reduction of parathyroid hormone (PTH) to predict surgical outcome in patients with primary hyperparathyroidism, and therefore contributes to the change of parathyroidectomy to a minimally invasive procedure. In this review, recent progress in applying ioPTH monitoring to patients with secondary and tertiary hyperparathyroidism and other testing areas is discussed. In-suite cortisol monitoring facilitates the use of adrenal vein sampling (AVS) for the differential diagnosis of primary aldosteronism and adrenocorticotropic hormone (ACTH)-independent Cushing syndrome. In clinical and psychological research settings, POC testing is also useful for rapidly assessing cortisol in plasma and saliva samples as a biomarker of stress. Careful resource utilization and coordination among stakeholders help to determine the best approach for implementing cost-effective POC testing. Technical advances in integrating appropriate biosensors with microfluidics-based devices hold promise for future real-time POC cortisol monitoring.

Parathyroid hormone as a marker for hypoperfusion in trauma: A prospective observational study

BACKGROUND

Hyperparathyroidism is common in critical illness. Intact parathyroid hormone has a half-life of 3 minutes to 5 minutes due to rapid clearance by the liver, kidneys, and bone. In hemorrhagic shock, decreased clearance may occur, thus making parathyroid hormone a potential early marker for hypoperfusion. We hypothesized that early hyperparathyroidism predicts mortality and transfusion in trauma patients.

METHODS

A prospective observational study was performed at a Level I trauma center in consecutive adult patients receiving the highest level of trauma team activation. Parathyroid hormone and lactic acid were added to the standard laboratory panel drawn in the trauma bay on arrival, before the administration of any blood products. The primary outcomes assessed were transfusion in 24 hours and mortality.

RESULTS

Forty-six patients were included. Median age was 47 years, 82.6% were men, 15.2% suffered penetrating trauma, and 21.7% died. Patients who were transfused in the first 24 hours (n = 17) had higher parathyroid hormone (182.0 pg/mL vs. 73.5 pg/mL, p < 0.001) and lactic acid (4.6 pg/mL vs. 2.3 pg/mL, p = 0.001). Patients who did not survive to discharge (n = 10) also had higher parathyroid hormone (180.3 pg/mL vs. 79.3 pg/mL, p < 0.001) and lactic acid (5.5 mmol/L vs. 2.5 mmol/L, p = 0.001). For predicting transfusion in the first 24 hours, parathyroid hormone has an area under the receiver operating characteristic curve of 0.876 compared with 0.793 for lactic acid and 0.734 for systolic blood pressure. Parathyroid hormone has an area under the receiver operating characteristic curve of 0.875 for predicting mortality compared with 0.835 for lactic acid and 0.732 for systolic blood pressure.

CONCLUSION

Hyperparathyroidism on hospital arrival in trauma patients predicts mortality and transfusion in the first 24 hours. Further research should investigate the value of parathyroid hormone as an endpoint for resuscitation.

LEVEL OF EVIDENCE

Prognostic, level II.

A sensitive electrochemical sensor for in vitro detection of parathyroid hormone based on a MoS2-graphene composite

This paper reports a biosensor based on a MoS2-graphene (MG) composite that can measure the parathyroid hormone (PTH) concentration in serum samples from patients. The interaction between PTH and MG was analysed via an electrochemical sensing technique. The MG was functionalized using l-cysteine. Following this, PTH could be covalently immobilized on the MG sensing electrode. The properties of MG were evaluated using scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectrometry. Following optimization of immobilized materials-such as MG, PTH, and alkaline phosphatase (ALP)-the performance of the MG sensor was investigated via cyclic voltammetry, to assess its linearity, repeatability, and reproducibility. Electrochemical impedance spectroscopy was performed on graphene oxide (GO) and MG-modified electrodes to confirm the capture of a monoclonal antibody (MAb) targeting PTH. Furthermore, the ALP-PTH-MG sensor exhibits a linear response towards PTH from artificial serum over a range of 1-50 pg mL-1. Moreover, patient sera (n = 30) were evaluated using the ALP-PTH-MG sensor and compared using standard equipment (Roche E 170). The P-value is less than 0.01 when evaluated with a t-test using Welch's correction. This implies that the fabricated sensor can be deployed for medical diagnosis.

Optimisation and validation of a new analytical method for the determination of four natural and synthetic hormones using LC-ESI-MS/MS

A rapid liquid chromatographic-tandem mass spectrometric method was developed for the simultaneous determination of four natural and synthetic hormone residues (progesterone, testosterone, trenbolone acetate and zeranol) in animal tissue samples. Sample preparation was optimised to minimise time and solvent consumption. Meat samples were mechanically homogenised and digested in a procedure that gave similar recoveries to those enzymatically hydrolysed by Helix pomatia. Efficient extraction was achieved using acidified acetonitrile (1% acetic acid). Chromatographic conditions were optimised to minimise matrix effects. Analytes were separated using a C18 column with gradient elution using ammonium formate solution in methanol (MeOH)/water (1:9) and MeOH mobile phases. Finally, residues were qualitatively and quantitatively determined by electrospray ionisation tandem mass spectrometry in multiple reaction monitoring mode. Different parameters for LC-MS/MS (e.g., declustering potential and collision energy) were optimised using API 6500QT; all analytes were measured using positive-mode electrospray ionisation (ESI⁺) except zeranol which was measured in negative mode (ESI^-). Due to LC-MS/MS signal enhancement/suppression, the determination of hormones was based on matrix-matched standard calculations. The method was validated for the four hormones on meat samples at different fortification levels and showed accepted performance criteria according to European Commission Decision 2002/657/EC. Decision limits and detection capabilities were estimated for all analytes.

Does Rapid Intraoperative Parathyroid Hormone Analysis Predict Cure in Patients Undergoing Surgery for Primary Hyperparathyroidism?

Background and Aims:

Preoperative 99mTc-sestamibi scintigraphy is used by many surgeons to identify the anatomical location of pathological parathyroid glands in patients undergoing surgical treatment for hyperparathyroidism. However, false negative results do occur. It has been suggested that intraoperative parathyroid hormone (PTH) analysis may enhance the possibility of performing successful focused, unilateral neck surgery in these patients. This study aimed to evaluate whether an adequate fall in intraoperative parathyroid hormone values predicts the removal of all hyperfunctioning parathyroid tissue and postoperative normocalcemia.

Material and Methods:

One hundred consecutive patients undergoing surgery for hyperparathyroidism had preoperative 99mTc-sestamibi scintigraphy and intraoperative parathyroid hormone (PTH) analysis. A fall in intraoperative PTH value by more than 50% of baseline value ended the procedure. This prospective study presents the clinical and biochemical results.

Results:

The overall sensitivity of the 99mTc-sestamib scintigraphy was 88% and for single adenomas 95%. The scintigraphy failed to detect the correct pathology in all cases with multiglandular disease (7 patients). A fall in intraoperative PTH value by more than 50% of baseline value was achieved in all patients. The combination of intraoperative PTH analysis and 99mTc-sestamibi scintigraphy enabled us to limit the operation to a focused, unilateral operation in 87 of the 100 patients. All patients were normocalcemic postoperatively.

Conclusions:

A fall in intraoperative PTH value more than 50 % of baseline value seems to predict postoperative normocalcemia and the removal of all hyperfunctioning parathyroid tissue. Bilateral neck exploration is avoided in the majority of patients.

Point-of-care diagnostics for niche applications

Point-of-care or point-of-use diagnostics are analytical devices that provide clinically relevant information without the need for a core clinical laboratory. In this review we define point-of-care diagnostics as portable versions of assays performed in a traditional clinical chemistry laboratory. This review discusses five areas relevant to human and animal health where increased attention could produce significant impact: veterinary medicine, space travel, sports medicine, emergency medicine, and operating room efficiency. For each of these areas, clinical need, available commercial products, and ongoing research into new devices are highlighted.

Intra-operative parathyroid hormone monitoring through central laboratory is accurate in renal secondary hyperparathyroidism

OBJECTIVE

The usefulness, the methods and the criteria of intra-operative monitoring of the parathyroid hormone (ioPTH) during parathyroidectomy (PTX) for renal secondary hyperparathyroidism (rSHPT) in patients on chronic hemodialysis remain still matter of debate. The present study aimed to evaluate the ability of a low cost central-laboratory second generation PTH assay to predict an incomplete resection of parathyroid glands (PTG).

METHODS

The ioPTH decay was determined In 42 consecutive patients undergoing PTX (15 subtotal and 27 total without auto-transplant of PTG) for rSHPT. The ioPTH monitoring included five samples: pre-intubation, post-manipulation of PTG and at 10, 20 and 30min post-PTG excision. The patients with PTH exceeding the normal value (65pg/ml) at the first postoperative week, 6 and 12months were classified as persistent rSHPT.

RESULTS

The concentrations of ioPTH declined significantly over time in patients who received total or subtotal PTX; however, no difference was found between the two types of PTX. Irrespective of the type of PTX and the number of PTG removed, combining the absolute and percentage of ioPTH decay at 30min after PTG excision, we found high sensitivity (100%), specificity (92%), negative predictive value (100%) and accuracy (93%) in predicting the persistence of rSHPT.

CONCLUSIONS

The monitoring of the ioPTH decline by a low cost central-laboratory second generation assay is extremely accurate in predicting the persistence of disease in patients on maintenance hemodialysis undergoing surgery for rSHPT.

Imaging of the parathyroid glands in primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) is one of the most frequent endocrine diseases worldwide. Surgery is the only potentially curable option for patients with this disorder, even though in asymptomatic patients 50 years of age or older without end organ complications, a conservative treatment may be a possible alternative. Bilateral neck exploration under general anaesthesia has been the standard for the definitive treatment. However, significant improvements in preoperative imaging, together with the implementation of rapid parathyroid hormone determination, have determined an increased implementation of focused, minimally invasive surgical approach. Surgeons prefer to have a localization study before an operation (both in the classical scenario and in the minimally invasive procedure). They are not satisfied by having been referred a patient with just a biochemical diagnosis of PHPT. Imaging studies must not be utilized to make the diagnosis of PHPT. They should be obtained to both assist in determining disease etiology and to guide operative procedures together with the nuclear medicine doctor and, most importantly, with the surgeon. On the contrary, apart from minimally invasive procedures in which localization procedures are an obligate choice, some surgeons believe that literature on parathyroidectomy over the past two decades reveals a bias towards localization. Therefore, surgical expertise is more important than the search for abnormal parathyroid glands.

Role of intraoperative PTH monitoring and surgical approach in primary hyperparathyroidism

AIMS

The use of intraoperative PTH monitoring (IOPTH) in combination with preoperative imaging has been useful to surgeons performing minimally invasive parathyroidectomy principally for adequacy of excision. However, its role within patients with equivocal imaging remains less clear particularly regarding the reduction of bilateral neck explorations. This study investigated the influence of IOPTH monitoring on the type of surgical approach adopted for patients with primary hyperparathyroidism (PHPT). Specifically, determining its impact amongst patients with equivocal imaging results.

METHODS

165 patients undergoing parathyroidectomy for PHPT at a single institution by a single surgeon, between 2008 and 2012, were included. Patients were divided into 2 groups, IOPTH monitoring and non-IOPTH monitoring. They were sub-classified according to their imaging strengths: strongly positive, equivocal and negative imaging. The percentages of patients undergoing focused, unilateral and bilateral operations were determined.

RESULTS

108 patients had IOPTH monitoring and 57 patients did not based on the availability of IOPTH monitoring. Patients with strongly positive imaging had a higher frequency of focused operation in both groups; IOPTH 73.4% and non-IOPTH 71.4%. Patients with negative imaging results had a higher frequency of bilateral operations; IOPTH 77.8% and non-IOPTH 72.7%. In patients with equivocal imaging results more focused/unilateral operations were performed with IOPTH monitoring 66.6% versus non-IOPTH 25%. The use of intraoperative PTH increased the likelihood of a unilateral procedure with equivocal imaging compared to those with negative imaging p = 0.04.

CONCLUSION

IOPTH monitoring is most useful as an adjunct to preoperative imaging when imaging results are equivocal allowing for more focused/unilateral operations to be performed.

Early predictors of hypocalcemia after total thyroidectomy: an analysis of 304 patients using a short-stay monitoring protocol

IMPORTANCE

Postoperative hypocalcemia is common after total thyroidectomy, and perioperative monitoring of serum calcium levels is arguably the primary reason for overnight hospitalization. Confidently predicting which patients will not develop significant hypocalcemia may allow for a safe earlier discharge.

OBJECTIVE

To examine associations of patient characteristics with hypocalcemia, duration of hospitalization, and postoperative intact parathyroid hormone (IPTH) level after total thyroidectomy.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective study of consecutive patients who underwent total thyroidectomy by a single high-volume surgeon between February 1, 2010, and November 30, 2012. Postoperative serum 25-hydroxyvitamin D (vitamin D), calcium, and IPTH levels were tested within 6 to 8 hours after surgery. Mild hypocalcemia was defined as any postoperative serum calcium level of less than 8.4 to 8.0 mg/dL. Significant hypocalcemia was defined as any postoperative serum calcium level of less than 8.0 mg/dL or the development of hypocalcemia-related symptoms.

INTERVENTIONS

Total thyroidectomy.

MAIN OUTCOMES AND MEASURES

Associations of patient demographic and clinical characteristics and laboratory values with postoperative mild and significant hypocalcemia were examined using univariate analysis, and independent predictors of hypocalcemia, duration of hospitalization, and IPTH level were determined using multivariate analysis.

RESULTS

Overall, 304 total thyroidectomies were performed. Mild and significant hypocalcemia occurred in 68 (22.4%) and 91 (29.9%) patients, respectively, of which the majority were female (P = .003). The development of significant hypocalcemia was associated with postoperative IPTH level (P < .001). On multivariate analysis, males had a decreased risk of developing mild (odds ratio, 0.37 [95% CI, 0.16-0.85]) and significant (odds ratio, 0.57 [95% CI, 0.09-0.78]) hypocalcemia. Every 10-pg/mL increase in postoperative IPTH level predicted a 43% decreased risk of significant hypocalcemia (P < .001) and an 18% decreased risk of hospitalization beyond 24 hours (P = .03). Presence of malignant neoplasm carried a 27% risk of mild hypocalcemia (P = .02). There was a progressively increasing risk of lower IPTH levels for each parathyroid gland inadvertently resected or autotransplanted. Male sex and African American race were independently predictive of higher IPTH levels.

CONCLUSIONS AND RELEVANCE

Low postoperative IPTH level, female sex, and presence of malignant neoplasm are all significant, independent predictors of hypocalcemia after total thyroidectomy. Clinicians should consider these variables when deciding how to best manage or prevent postoperative hypocalcemia.

Perioperative androstenedione kinetics in women undergoing laparoscopic ovarian drilling: a prospective study

We evaluated perioperative androstenedione levels in laparoscopic ovarian drilling (LOD) for polycystic ovary syndrome (PCOS) and whether an intraoperative androstenedione change was predictive for spontaneous ovulation. In a prospective study, 21 anovulatory women with clomiphene citrate-resistant PCOS who underwent LOD and eight female controls who underwent diagnostic laparoscopy for infertility were included. Perioperatively, blood was drawn one day before surgery, directly before skin incision, ten minutes after surgery, and after two days. Within three months, spontaneous ovulation occurred in 15 women (71.4 %). For both the PCOS and the control group, an androstenedione increase was found from one day before surgery to skin incision (p < 0.05). In PCOS women, there was an intraoperative androstenedione decrease (median 3.5, IQR 2.2-4.8 vs. median 2.6, IQR 1.4-2.6 ng/ml, p = 0.002). In multivariate analysis, only higher preoperative androstenedione (odds ratio, OR 6.53) and luteinizing hormone levels (OR 7.31), as well as secondary infertility (OR 5.40), were associated with higher rates of postoperative spontaneous ovulation (p < 0.001). Androstendione declines significantly during LOD. However, intraoperative kinetics are not useful for the prediction of spontaneous ovulation after LOD, in contrast to preoperative androstenedione and LH levels, as well as a history of previous pregnancies.

Fast intraoperative testosterone assay confirms the location of an ovarian virilizing tumor in a young girl

The detection of testosterone-producing ovarian tumors in childhood and adolescence by imaging techniques only can be difficult because of the tumors' radiological structure and sometimes diminutive size. We describe an 11.5-year-old girl with a 9-month history of voice deepening, mild hirsutism, minor acne, increased growth velocity, weight gain, and clitoromegaly. Laboratory investigation revealed an extremely elevated serum testosterone level without any additional endocrine abnormalities. Abdominal ultrasound and MRI showed a sparsely noticeable solid mass in the center of the right ovary. At laparotomy, blood was selectively drawn from the right and the left ovarian veins. Rapid testosterone measurement revealed a 70-fold higher testosterone concentration in the right ovarian vein within 45 min. Based on this finding, a right salpingo-oophorectomy was performed. The patient's postoperative testosterone level declined within 24 h. The histopathological diagnosis was Leydig cell tumor. In conclusion, the implementation of a fast intraoperative testosterone assay enabled the localization and curative therapy of a Leydig cell tumor. This technique seems to be a good alternative to preoperative selective venous blood sampling when body imaging does not unveil the tumor's site.

Gastroenteropancreatic neuroendocrine tumors in multiple endocrine neoplasia type 1

We reviewed the literature about entero-pancreatic neuroendocrine tumors in Multiple Endocrine Neoplasia type 1 syndrome (MEN1) to clarify their demographic features, localization imaging, practice, and appropriate therapeutical strategies, analyzing the current approach to entero-pancreatic neuroendocrine tumors in MEN1. Despite the fact that hyperparathyroidism is usually the first manifestation of MEN1, the penetrance of these tumors is similar. They are characterized by multiplicity of lesions, variable expression of the tumors, and propensity for malignant degeneration. Both the histological type and the size of MEN1 neuroendocrine tumors correlate with malignancy. Monitoring of pancreatic peptides and use of imaging exams allow early diagnosis and prompt surgical treatment, resulting in prevention of metastatic disease and improvement of long-term survival. Surgery is often the treatment of choice for MEN1-neuroendocrine tumors. The rationale for surgical approach is to curtail malignant progression of the disease, and to cure the associated biochemical syndrome, should it be present.

The necessity and reliability of intraoperative parathyroid hormone (PTH) testing in patients with mild hyperparathyroidism and PTH levels in the normal range

BACKGROUND

Intraoperative parathyroid hormone (IoPTH) testing is useful in the management of hyperparathyroidism. The successful removal of hypersecreting parathyroids is indicated by a decrease in PTH levels >50% within 15 min. A subset of patients with mild hyperparathyroidism will actually have starting PTH levels in the normal range. We sought to determine if IoPTH testing is necessary in these patients and if the 50% rule delineating surgical cure is reliable.

METHODS

A retrospective review was performed on all patients who underwent parathyroidectomy for hyperparathyroidism at a single institution from 3/2001 to 8/2008.

RESULTS

Of the 1,001 patients, 142 (14%) had mild hyperparathyroidism and normal baseline PTH levels (<65 pg/ml). Their mean PTH was 59 ± 1 pg/ml. During surgery, 105 (74%) had a >50% decline in PTH levels after resection of hyperfunctioning parathyroid glands, and their operations were terminated. In contrast, 37 (26%) patients did not have a >50% decline in PTH levels leading to further surgical exploration. In these 37 patients, the PTH levels fell by >50% after the removal of the additional glands in 25 patients (17.6%) and dropped after 20 min in 7 patients (4.9%). In 5 patients (3.5%) the IoPTH did not drop. Of the 142 total patients, 91 had single adenomas and 51 patients had multi-gland disease. All patients (100%) were cured (normal serum calcium after 6 months).

CONCLUSIONS

Intraoperative PTH testing plays an important role in the operative management in 14% of patients with mild hyperparathyroidism. Importantly, a 50% decline in IoPTH level within 15 min of parathyroidectomy is 96.5% reliable in predicting cure in these patients with PTH starting in the normal range.

Challenges for the endocrine laboratory in critical illness

The endocrine laboratory must provide accurate and timely results for the critically ill patient. A number of pathophysiological factors affect assay systems for adrenal, thyroid and gonadal function tests. The effects are primarily on estimates of 'free hormone' concentration through abnormal binding protein concentrations and the effects of drugs and metabolites on hormone-protein binding. The limitations of the principal analytical techniques (immunoassay and chromatography-mass spectrometry) include drug effects, endogenous antibody interference and ion suppression. These effects are not always easily identified. Analytical specificity and standardisation result in differences in bias between assays and thus a requirement for assay specific decision limits and reference ranges. Good communication between clinician and laboratory is needed to minimise these effects. Developments in mass spectrometry should lead to greater sensitivity and wider applicability of the technique. International efforts to develop higher order reference materials and reference method procedures should lead to greater comparability of results.

Rapid intraoperative parathyroid hormone assay in the surgical management of hyperparathyroidism

CONTEXT

Historically, successful surgical management of primary hyperparathyroidism has required bilateral exploration of the neck. By confirming complete removal of hypersecreting tissue, an intraoperative parathyroid hormone (IO-PTH) assay allows use of a more limited procedure.

OBJECTIVE

Our objective was to evaluate the utility of IO-PTH assay used in 32 parathyroid explorations versus conventional bilateral exploration used before the advent of IO-PTH assays.

METHODS

Minimally invasive parathyroidectomy (MIP) was used. Plasma samples were obtained at several intervals and were analyzed for IO-PTH by use of a rapid immunochemiluminescent assay (ICMA). Outcomes were assessed by univariate inferential testing, yielding one-tailed t-test results.

RESULTS

The study group had a mean plasma IO-PTH level decrease of 87% at ten minutes after excision. All 32 patients who underwent MIP using IO-PTH monitoring had successful surgery. At last postoperative follow-up examination, all 32 patients were normocalcemic. There were statistically significant decreases in duration of surgery, length of hospital stay, and surgery cost.

CONCLUSIONS

IO-PTH levels predicted the postoperative outcome for all patients studied, can provide valuable information to surgeons, and can decrease the duration of surgery and hospital stay.

Reliable early prediction for different types of post-thyroidectomy hypocalcemia

Objectives

High incidence of hypocalcemia after thyroidectomy is a major determinant in delay of discharge. Even though many studies have focused on the search for reliable early predictors of postoperative hypocalcemia, definitions of hypocalcemia are diverse; therefore, interpretation and application of previously reported findings may not be easy. We aimed to elucidate diverse patterns of post-thyroidectomy hypocalcemia and to provide reliable early predictors for these different types of hypocalcemia.

Methods

Retrospective chart review was performed and eligible 112 patients of thyroidectomy were categorized into four groups according to symptomatic and/or biochemical hypocalcemic criteria. A mismatch of occurrence and the timing of symptomatic or biochemical abnormalities were evaluated. Predictive values of commonly used biomarkers were compared in each group; levels of serum total calcium and ionized calcium, and intact parathyroid hormone (PTH).

Results

Among 62 hypocalcemic patients, 45 patients (72.5%) experienced both symptomatic and biochemical abnormalities during hospitalization. A mismatch on the timing of initial detection of symptomatic and biochemical hypocalcemia was observed in 21 patients (46.6%). Intact PTH level measured at 1 hour was a useful indicator in prediction of symptomatic hypocalcemia with 79.7-87.4% of diagnostic accuracy. Serum ionized calcium measured next morning after surgery was a reliable predictor of biochemical hypocalcemia with 77.9-94.8% of diagnostic accuracy.

Conclusion

For the safety of patients, the possibility of both symptomatic and biochemical hypocalcemia should be considered together before deciding early discharge. Using intact PTH for symptomatic hypocalcemia and day-1 ionized serum calcium level for biochemical hypocalcemia will be helpful for the reliable prediction of heterogeneous nature of postoperative hypocalcemia.

Intraoperative adjuncts for parathyroid surgery

In recent years, parathyroid surgery has evolved from traditional bilateral neck exploration to minimal invasive parathyroidectomy. This trend became possible due to preoperative localization imaging that guides the surgeon in the search for a parathyroid adenoma. Intraoperative adjuncts are complementary to preoperative localization and assist in localizing parathyroid glands, confirming parathyroid tissue and establishing a cure. Institutions and surgeons utilize different intraoperative adjuncts in different protocols with varying results. The purpose of this article is to review the available intraoperative adjuncts to parathyroid surgery and critically evaluate their utility, accuracy and their added value to the surgeon.

A fast intraoperative PTH point-of-care assay on the Philips handheld magnotech system

Background

Intraoperative parathyroid hormone (ioPTH) is used during minimally invasive parathyroidectomy (MIP) to predict the success of surgery and should be accurate with a short turnaround time.

Material and method

We developed an ioPTH point-of-care (POC) assay on Philips handheld magnotech system. Magnotech technology is based on magnetically controlled movement of superparamagnetic nanoparticles in stationary sample fluid. During first phase, intact-PTH is captured by magnetic particles coated with anti-N-terminal-PTH antibodies. Subsequently, magnetic particles are collected by magnetic forces at sensor surface coated with anti-C-terminal-PTH antibodies. Unbound/nonspecifically bound particles are pulled away from detection surface, using a second magnetic force. Amount of specifically bound particles is measured using a surface-sensitive optical imaging technique.

Results

ioPTH test could be performed with a turnaround time of less than 10 min and could detect low intact-PTH concentrations (picomolar). Integrated cartridge contains a blood separation filter and dry reagents for the assay.

Conclusion

The next magnotech ioPTH assay will be the only POC test able to give accurate results in less than 10 min, using 25 μL of whole blood. Thanks to the ease-of-use, magnotech ioPTH could be performed in the operating theater by any member of surgical staff.

Prediction of hypocalcemia after using 1- to 6-hour postoperative parathyroid hormone and calcium levels: an analysis of pooled individual patient data from 3 observational studies

BACKGROUND

Parathyroid hormone (PTH) levels up to 6 hours postthyroidectomy have been shown to have excellent predictive power in determining hypocalcemia. In this study, we investigate the usefulness of combining calcium and PTH to increase the predictive power.

METHODS

Individual patient data were obtained from 3 studies (152 patients) that fulfilled our criteria (using PTH assay within hours postthyroidectomy to predict symptomatic hypocalcemia).

RESULTS

Changes in combined PTH and calcium threshold levels checked 1 to 6 hours after thyroidectomy were excellent in predicting postoperative hypocalcemia. A decrease in PTH of 60%, coupled with a simultaneous decrease in calcium of 10%, 5 to 6 hours postoperatively resulted in a sensitivity and specificity of 100%. However, combined PTH and calcium threshold changes were not significantly better than using PTH threshold changes alone.

CONCLUSIONS

Threshold changes in serum calcium and PTH, checked hours after surgery, can be used together to accurately predict whether a patient will become hypocalcemic after thyroidectomy.

Monitoring endocrine function

This article reviews current knowledge concerning the monitoring of endocrine function in patients in the clinical setting. Monitoring techniques are discussed and literature is reviewed regarding diabetes mellitus, thyroid, and parathyroid disorders, pheochromocytoma, adrenal insufficiency, and carcinoid tumors.

Implantable diagnostic device for cancer monitoring

Biopsies provide required information to diagnose cancer but, because of their invasiveness, they are difficult to use for managing cancer therapy. The ability to repeatedly sample the local environment for tumor biomarker, chemotherapeutic agent, and tumor metabolite concentrations could improve early detection of metastasis and personalized therapy. Here we describe an implantable diagnostic device that senses the local in vivo environment. This device, which could be left behind during biopsy, uses a semi-permeable membrane to contain nanoparticle magnetic relaxation switches. A cell line secreting a model cancer biomarker produced ectopic tumors in mice. The transverse relaxation time (T(2)) of devices in tumor-bearing mice was 20+/-10% lower than devices in control mice after 1 day by magnetic resonance imaging (p<0.01). Short term applications for this device are numerous, including verification of successful tumor resection. This may represent the first continuous monitoring device for soluble cancer biomarkers in vivo.

Predictors of intra-operative parathyroid hormone decline in subjects operated for primary hyperparathyroidism by minimally invasive parathyroidectomy

BACKGROUND

The predictors of intra-operative PTH (IOPTH) decline during minimally invasive parathyroidectomy (MIP) for primary hyperparathyroidism have been but poorly studied.

MATERIALS AND METHODS

This retrospective study included 108 patients who underwent MIP for a single adenoma. Serum calcium and phosphorus were measured before surgery and 1 day post-operatively. IOPTH was measured before (intra-operative preincision or PTHt0) and 10 min after removal of the adenoma (PTHt10). The Modification of Diet in Renal Disease (MDRD) equation was used to estimate the glomerular filtration rate. The weight of the adenoma was assessed in all the subjects.

RESULTS

The sex ratio female/male was 5.37 with a mean age of 57.3 yr. The mean pre- and postoperative values were for calcium 2.80 and 2.19 mmol/l, respectively (p<0.0001) and for phosphorus 0.90 and 1.16 mmol/l, respectively (p<0.0001). The PTH dropped from a mean value of 184.8 to 50.8 pg/ml 10 min after adenoma resection with a mean drop of 69.7%. Thirteen patients (12%) did not achieve a PTH fall of more than 50%. In a bivariate analysis, age, an MDRD<60 ml/min and weight of adenoma were inversely associated with IOPTH fall (p=0.009, p=0.004, and p<0.001, respectively) while gender, body mass index, hypertension, diabetes, pre-operative phosphorus and calcium had no significant effects. In the multivariate analysis, age, weight of adenoma, and MDRD were still independent negative predictors of the IOPTH fall (p=0.01, p=0.018, and p<0.001, respectively).

CONCLUSION

Our results suggest that during MIP the presence of a parathyroid adenoma with a high weight, in an elderly subject or in a subject with altered renal function, will result in a lesser degree of IOPTH fall.

Optical scanner for immunoassays with up-converting phosphorescent labels

A 2-D optical scanner was developed for the imaging and quantification of up-converting phosphor (UCP) labels in immunoassays. With resolution better than 500 microm, a scan rate of 0.4 mm/s, and a 1-2% coefficient of variation for repeatability, this scanner achieved a detection limit of fewer than 100 UCP particles in an 8.8. x 10(4) microm(2) area and a dynamic range that covered more than three orders of magnitude. Utilizing this scanner, a microfluidic chip immunoassay for the cytokine interferon-gamma (IFN-gamma) was developed: concentrations as low as 3 pM (50 pg/mL) were detected from 100 microL samples with a total assay time of under an hour, including the 8 min readout. For this UCP-based assay, 2-D images of the capture antibody lines were scanned, image processing techniques were employed to extract the UCP emission signals, a response curve that spanned 3-600 pM IFN-gamma was generated, and a five-parameter logistic mathematical model was fitted to the data for determination of unknown IFN-gamma concentrations. Relative to common single-point or 1-D scanning optical measurements, our results suggest that a simple 2-D imaging system can speed assay development, reduce errors, and improve accuracy by characterizing the spatial distribution and uniformity of surface-captured optical labels as a function of assay conditions and device parameters.