Third-generation Parathyroid Hormone Assays Research Articles

Diagnostic Values of Intraoperative (1-84) Parathyroid Hormone Levels are Superior to Intact Parathyroid Hormone for Successful Parathyroidectomy in Patients With Chronic Kidney Disease

ObjectivePersistent secondary hyperparathyroidism (SHPT) may occur because of residual cervicothoracic parathyroids in parathyroidectomy (PTX) patients with chronic kidney disease. We prospectively compared the predictive values of intraoperative plasma (1-84) parathyroid hormone (PTH) and intact PTH (iPTH) levels to improve the safety and efficacy of PTX. MethodsWe included 100 healthy controls, 162 stage 5 chronic kidney disease patients without SHPT, and 214 patients who underwent PTX because of SHPT. Plasma iPTH and (1-84) PTH levels were measured before incision (io-iPTH0 and io-[1-84]PTH0, respectively) and 10 minutes (io-iPTH10 and io-[1-84]PTH10, respectively) and 20 minutes (io-iPTH20 and io-[1-84]PTH20, respectively) after removing all parathyroids. The percentage reduction of iPTH and (1-84) PTH at 10 minutes (io-iPTH10% and io-[1-84]PTH10%, respectively) and 20 minutes (io-iPTH20%, and io-[1-84]PTH20%, respectively) was calculated. iPTH and (1-84) PTH were measured using second- and third-generation PTH assays, respectively. ResultsCompared with the controls and non-PTX patients, the PTX group had more obvious mineral metabolism disorders. There were 187 successful PTXs, 19 patients with persistent SHPT, and 8 patients lost to follow-up. The receiver operating characteristic curves revealed that io-(1-84)PTH10% >86.6% and io-(1-84)PTH20% >87.5% suggested successful PTX. The sensitivity of io-iPTH20% and io-(1-84)PTH20% were higher than those at the timepoint of 10 minutes. Moreover, the specificity and sensitivity of the (1-84) PTH reduction percentage were superior to that of iPTH. ConclusionIntraoperative reduction percentages of plasma (1-84) PTH levels are superior to iPTH for accurately predicting successful PTX, especially at 20 minutes after all cervicothoracic parathyroids had been resected.

Vitamin D, bone alkaline phosphatase and parathyroid hormone in healthy subjects and haemodialysed patients from West Africa: impact of reference ranges and parathyroid hormone generation assays on the KDIGO guidelines.

BackgroundThe Kidney Disease: Improving Global Outcomes (KDIGO) guidelines recommend targets based on multiples of the upper limit of normal (ULN) of parathyroid hormone (PTH) concentration. However, the ULN has not always been correctly established by manufacturers. While it is known that the ULN is supposed to be higher in African Americans than in Caucasians, it is largely unknown in Africans.MethodsWe established the ULN of PTH concentration in a population of 240 healthy Ivorians using second- and third-generation PTH assays before and after supplementation with 100 000 IU of cholecalferol. We measured the levels of PTH, bone alkaline phosphatase, 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D in 100 haemodialysed Ivorian patients.ResultsThe prevalence of vitamin D deficiency in Ivory Coast is low. The ULN obtained using the third-generation PTH assay was similar to that obtained in Caucasians but was higher when PTH was measured using the second-generation PTH assay. According to the KDIGO guidelines, ∼20% of the haemodialysed patients were below twice the ULN and 30% were above nine times the ULN. Approximately 25% of the patients were even >12 times the ULN. We observed a discrepancy in the results between the two PTH assays (14%) that was relatively more important than what we observed from previous studies in Caucasians using the same strategy.ConclusionsWe found a low prevalence of vitamin D deficiency in a tropical country like Ivory Coast. We also established the PTH reference range, which could prove useful for the follow-up of haemodialysed patients, particularly for the large number of patients suffering from secondary hyperparathyroidism who are at high risk of adverse bone events.

Serum PTH reference values established by an automated third-generation assay in vitamin D-replete subjects with normal renal function: consequences of diagnosing primary hyperparathyroidism and the classification of dialysis patients.

To determine parathyroid hormone (PTH) reference values in French healthy adults, taking into account serum 25-hydroxyvitamin D (25OHD), renal function, age, gender, and BMI. We studied 898 healthy subjects (432 women) aged 18-89 years with a normal BMI and estimated glomerular filtration rate (eGFR), 81 patients with surgically proven primary hyperparathyroidism (PHPT), and 264 dialysis patients. 25OHD and third-generation PTH assays were implemented on the LIAISON XL platform. Median PTH and 25OHD values in the 898 healthy subjects were 18.8 ng/l and 23.6 ng/ml respectively. PTH was lower in subjects with 25OHD ≥30 ng/ml than in those with lower values. Among the 183 subjects with 25OHD ≥30 ng/ml, those aged ≥60 years (n=31) had higher PTH values than younger subjects, independent of 25OHD, BMI, and eGFR (P<0.001). Given the small number of subjects aged ≥60 years, we adopted the 95% CI of PTH values for the entire group of 183 vitamin D-replete subjects (9.4-28.9 ng/l) as our reference values. With 28.9 ng/l as the upper limit of normal (ULN) rather than the manufacturer's ULN of 38.4 ng/l, the percentage of PHPT patients with 'high' PTH values rose to 90.1% from 66.6% (P<0.001), and 18.6% of the dialysis patients were classified differently in view of the KDIGO target range (two to nine times the ULN). When only subjects with 25OHD ≥30 ng/ml were included in the reference population, the PTH ULN fell by 22.4%, diagnostic sensitivity for PHPT improved, and the classification of dialysis patients was modified.

Critical issues of PTH assays in CKD

Measurement of bioactive parathyroid hormone (PTH) is essential for the optimal management of secondary hyperparathyroidism and its associated bone disorders in chronic kidney disease (CKD) patients. For this purpose, three generations of increasingly specific PTH assays have been developed over the last 4 decades. To date, however, only second-generation PTH assays are most widely used, although these have been shown to cross-react with large PTH fragments having a partially preserved N-structure, mostly PTH(7-84). The newly developed third-generation PTH assays are believed to be the most specific means of measuring PTH(1-84), but their clinical utility remains debatable. More recently, these latter assays have also been shown to react with a new N-form of PTH, which has been identified in patients with severe hyperparathyroidism and parathyroid carcinoma. Progressive research in this area has advanced our understanding considerably regarding the circulating molecular forms of PTH and their pathophysiological roles in bone abnormalities associated with CKD. However, developing an ideal PTH assay continues to be difficult because of key issues such as the reliability of PTH as a surrogate marker for bone turnover, practicality of employing third-generation PTH assays, and unknown biological implications of N-PTH and other PTH fragments. Further research exploring these issues is mandatory to understand and optimally manage parathyroid disorders and bone abnormalities in CKD patients.

Lessons from second- and third-generation parathyroid hormone assays in primary hyperparathyroidism

Lessons from second- and third-generation parathyroid hormone assays in primary hyperparathyroidism

Lessons from a second- and third-generation parathyroid hormone assays in renal failure patients

Lessons from a second- and third-generation parathyroid hormone assays in renal failure patients

Third-generation parathyroid hormone assays and all-cause mortality in incident dialysis patients: the CHOICE study

There has been controversy about the utility of new third-generation parathyroid hormone (PTH) assays measuring only 1-84 PTH, with few large studies comparing second- and third-generation PTH measurements in patients with ESRD. We measured 1-84 PTH ('biointact' or 'whole' PTH) and total PTH ('intact' PTH) in a national cohort of 515 incident dialysis patients from banked frozen EDTA plasma (median follow-up, 35 months) and examined the accuracy of estimating 1-84 PTH from total PTH and the associations of these levels with patient characteristics and mortality. The 1-84 PTH and total PTH levels were closely correlated. Higher 1-84 PTH was associated with African-American race and higher serum phosphate and lower calcium levels. The percentage of total PTH represented by 1-84 PTH was, on average, 53%, but with a wide range (25-89%). Calculating 1-84 PTH from total PTH using a proposed standard conversion factor (54%) led to misclassification of 8% of the population compared with measured 1-84 PTH. In a multivariate Cox proportional hazards model for all-cause mortality, a 1-84 PTH value >160 pg/ml was associated with increased risk of mortality (HR = 1.62, 95% CI, 1.03-2.54) compared to a level of 80-160 pg/ml. Elevated total PTH, 7-84 PTH and the 1-84 PTH/7-84 PTH ratio were not significantly associated with mortality. The 1-84 PTH and total PTH are highly correlated. Elevated 1-84 PTH was significantly associated with increased mortality, whereas total PTH did not reach statistical significance. Thus, although in other respect they are similar, there may be utility in measuring 1-84 PTH for its associations with mortality.

Whole or Fragmentary Information on Parathyroid Hormone?

More than a decade ago, Brossard et al. (1) drew attention to the fact that the so-called “intact,” second-generation parathyroid hormone (PTH) assays measured not only the PTH-(1-84) molecule but also large PTH fragments in patients with chronic kidney disease (CKD). One of the major problems is that the proportion of PTH-(1-84) and its fragments in the circulation changes in response to the serum level of ionized calcium; therefore, in presence of hypercalcemia, the parathyroid gland releases less PTH-(1-84) but more PTH fragments. The reverse is true in the presence of hypocalcemia, where more active PTH-(1-84) is needed. The difference is particularly striking in patients with CKD. When considering the potential biologic relevance of this finding, it is even more disturbing that at least one of the fragments, namely PTH-(7-84), has been shown to act as a partial antagonist of PTH-(1-84), with opposite biologic activities (2–4). Progressive awareness of these methodologic problems and the underlying biologic complexity went along with the development of third-generation PTH assays that recognize only PTH-(1-84), also called “whole,” “bio-intact,” or “biologically active” PTH (5). Theoretically, the assessment of second- and third-generation PTH assays combined should reflect parathyroid activity more adequately than second-generation assays alone, reflecting the sum of potentially opposing effects of PTH-(1-84) and its fragments. …

Inter-method variability in PTH measurement: Implication for the care of CKD patients

The National Kidney Foundation/Kidney-Dialysis Outcome Quality Initiative guidelines recommend to maintain the serum intact parathyroid hormone (PTH) concentration between 150 and 300 ng/l in chronic kidney disease (CKD) stage 5 patients. As these limits were derived from studies that used the Allegro intact PTH assay, we aimed to evaluate whether they were applicable to other PTH assays. We compared the PTH concentrations measured with 15 commercial immunoassays in 47 serum pools from dialysis patients, using the Allegro intact PTH assay as the reference. We also evaluated the recovery of graded amounts of synthetic 1-84 and 7-84 PTH added separately to a serum pool. Although the assays were highly correlated, the concentrations differed from one assay to another. The median bias between the tested assays and the Allegro intact PTH assay ranged from -44.9 to 123.0%. When the PTH concentrations were 150 or 300 ng/l with the Allegro intact PTH assay, they ranged with other assays from 83 to 323 ng/l and from 160 to 638 ng/l, respectively. The tested assays recognized 7-84 PTH with various cross-reactivities, whereas a given amount of 1-84 PTH was recovered differently by these assays. We found important inter-method variability in PTH results owing to both antibody specificity and standardization reasons. The unacceptable consequence is that opposite therapeutic attitudes may be reached in a single patient depending on the PTH assay used. We propose to use assay-specific decision limits for CKD patients, or to apply a correcting factor to the PTH results obtained with a given assay.

Overproduction and Secretion of a Novel Amino-Terminal Form of Parathyroid Hormone from a Severe Type of Parathyroid Hyperplasia in Uremia

Measurement of bioactive parathyroid hormone (PTH) is essential for optimal management of bone abnormalities in dialysis patients. This can be accomplished by PTH measurements using third-generation PTH assays, which detect more or less of the first six amino acids of the PTH structure. Such assays do not detect non-(1-84) PTH fragments, such as human PTH (7-84), which are recognized by the second-generation PTH assays that use a detection antibody that recognizes an epitope within the 13-34 region of the PTH structure. Therefore, third-generation PTH results are expected to be lower than those that are obtained with second-generation PTH assays. Rare exceptions to this rule have been reported for patients with severe primary hyperparathyroidism or parathyroid cancer. Sera and gland extracts were analyzed from a dialysis patient with high bone turnover disease and with surprising higher PTH levels by a third-generation assay than by a second-generation assay. This finding normalized after the surgical removal of an enlarged gland with a single nodule, an advanced type of nodular hyperplasia. HPLC fractionation of sera and gland extracts revealed the overproduction and secretion of a PTH molecule with an intact amino-terminus structure distinct from (1-84) PTH. This form of PTH was readily detectable by third-generation PTH assays but was poorly reactive in second-generation PTH assays. Therefore, parathyroid glands with advanced uremic nodular hyperplasia may overproduce and secrete a novel, biologically active form of PTH with an intact 1-6 region but a presumably modified 12-18 region required for the detection in second-generation PTH assays.

Unexpected Serum Parathyroid Hormone Profiles in Some Patients with Primary Hyperparathyroidism

Third-generation parathyroid hormone (PTH) assays have been reported to measure only intact PTH(1-84), in contrast to second-generation assays, which also detect PTH(7-84) fragments. Higher PTH measurements were observed with third- than with second-generation PTH assays in a few patients with either severe primary hyperparathyroidism or parathyroid carcinoma. We analyzed biological data [second- and third-generation PTH assays, 25-hydroxyvitamin D (25-OHD), calcium, and phosphate concentrations] obtained before and after surgery for 2 groups of patients selected from a large series of consecutive patients with primary hyperparathyroidism (PHPT): 7 female patients with surgically and histologically confirmed PHPT (group 1) and a matched group (group 2). For group 1 but not group 2, PTH concentrations measured by third-generation PTH assays before surgery were higher than those measured by the second-generation assays. Circulating 25-OHD, calcium, and phosphate concentrations were similar in both groups. In addition, PTH values measured with the third-generation PTH assays in group 1 decreased after surgery. Our results confirm that third-generation PTH assays do not measure only PTH(1-84). The frequency of this unexpected finding of markedly lower PTH concentrations than previously reported was approximately 5% in patients with PHPT without malignancy. We do not know whether the presence of this unexpected profile is predictive of malignancy.