Comparison between Whole and Intact Parathyroid Hormone Assays

Abstract

The standard measurement of parathyroid hormone (PTH) is the intact PTH (iPTH) assay, which is used for approximately 90% of Japanese dialysis patients. The iPTH assay reacts not only with 1-84 PTH, but also with large truncated fragments of non-1-84 PTH, including 7-84 PTH. On the other hand, the whole PTH assay is specific for 1-84 PTH. The aim of the current study was to define the validity of both whole and intact PTH assays. A total of 738 hemodialysis patients were enrolled from twelve dialysis services. The serum PTH level was evaluated by both intact and whole PTH assays simultaneously. Non-1-84 PTH was determined by subtracting the whole PTH value from that of the intact PTH assay. The median level of whole PTH was 121 pg/mL, and that of iPTH was 210 pg/mL. The whole PTH assay had a very high correlation with the iPTH assay (r = 0.870, P < 0.001). For 43 out of 738 patients (5.8%) the value for intact PTH-whole PTH was <0. Both assays significantly correlated with non-1-84 PTH (P < 0.001), while the iPTH assay, particularly, had a very high correlation with non-1-84 PTH (r = 0.791). As a whole, 18% of the total population was misclassified into a different Japanese guideline category. Stratified by Japanese guideline classifications, 28% of patients within an iPTH target range were misclassified. Using Bland-Altman plot analysis, as the serum PTH level increased, there was a large difference between two assays. Both PTH assays correlate strongly, although the whole PTH assay may be more useful for precise evaluation of PTH function than the iPTH assay.

A 20-Year Study on 190 Patients With Primary Hyperparathyroidism in a Developing Country: Turkey Experience

“…4 This operation was followed by the discovery of parathormone and the development of many measurement methods of PTH. 5 In the last 30 years, the wide use of the multichannel autoanalyzer; use of USG, MIBI, computed tomography (CT), and MRI for the diagnosis of PHPT; and new surgical methods and techniques for the surgical treatment of PHPT have resulted in easier diagnosis of the disease, correct localization of pathologic lesions, and different surgical approaches. 1,[5][6][7][8][9][10][11][12][13][14][15][16][17] The aim of this study was to present our 20-yearexperience with 190 patients diagnosed with PHPT, their clinical features, diagnostic methods, surgical treatment and pathology, and review of the literature.…”

“…These new imaging and diagnostic methods include USG, MIBI scintigraphy, MRI, MIBI scintigraphy with the use of CT, and intraoperative adjuncts, such as a gamma probe with radioisotope sestamibi, intraoperative rapid PTH measurements, and the use of methylene blue or frozen section. [5][6][7][8][9][10][11][12][13][14][15][16][17] USG is a cheap, adequate, and noninvasive modality. Sensitivity of USG is associated with the user, the size and localization of the adenoma and concomitant thyroid disorder.…”

Quick parathyroid hormone assays: a comprehensive review of their utility in clinical practice

“…The whole PTH or third generation assay, on the other hand, exclusively reacts with the whole PTH molecule (1-84 fragment). 61 In comparison to the bioactive fragments, the non-1-84 fragments were reported to have a longer half-life. 62 Given the fact that the latter fragments are known to accumulate in renal failure patients, 63 false results would be likely if second generation assays were used for IPM in such patients.…”

LC-MS candidate reference methods for the harmonisation of parathyroid hormone (PTH) measurement: a review of recent developments and future considerations

“…Despite the improved performance of these assays in some patient groups [35], some anomalous results were still reported [36][37][38].…”

“…D'Amour and co-workers explored the exact structure of non-1-84 PTH fragments, using the array of second-and third-generation immunoassays that were then available, plus Edman degradation radio-sequencing with PTH with 35 S-labelled methionine residues. Samples from healthy controls were compared with individual clinical samples and sample pools from patients with confirmed parathyroid pathology and/or renal failure.…”