Assay-Specific Decision Limits for Two New Automated Parathyroid Hormone and 25-Hydroxyvitamin D Assays

Abstract

Background:The recent development of nonradioactive automated assays for serum parathyroid hormone (PTH) and 25-hydroxyvitamin D (25OHD) has made measurement of these two hormones possible in many laboratories. In this study, we compared two new assays for PTH and 25OHD adapted on an automated analyzer, the LIAISON ® , with two manual immunoassays used worldwide. Methods: We studied 228 osteoporotic patients, 927 healthy individuals, 38 patients with primary hyperparathyroidism, and 167 hemodialyzed patients. Serum PTH was measured with the Allegro ® and the LIAISON assays, and 25OHD was measured with DiaSorin RIA and the LIAISON assay. Regression analysis was used to calculate decision thresholds for the LIAISON assays that were equivalent to those of the Allegro PTH and DiaSorin 25OHD assays. Results: The 25OHD concentrations obtained with the LIAISON assay and the RIA in osteoporotic patients were well correlated (r ‫؍‬ 0.83; P <0.001). Regression and Bland-Altman analyses suggested that the LIAISON 25OHD assay reads lower than the DiaSorin RIA at low concentrations but higher at high concentrations. However, the cutoff (50 nmol/L) used in our laboratories to define vitamin D insufficiency with the DiaSorin RIA is applicable to the LIAISON 25OHD assay. In 927 healthy individuals, the 3rd-97th percentile intervals were 3-80 ng/L and 13-151 nmol/L for the LIAISON PTH and

High Total Protein Impairs Appropriate Gel Barrier Formation in BD Vacutainer Blood Collection Tubes

“…The random tendency observed whatever the concentrations measured did not permit the definition of a clear strategy concerning patient follow-up, particularly for those needing treatment with respect to their vitamin D status. The discrepancy between these 2 methods is consistent with either important negative (4,5 ) or positive (our data) intercepts traducing differences in the assay response to the calibrant matrix.…”

“…1B) suggested that CLIA results tended to be higher than RIA at low and high concentrations, conversely to data previously published (4 ). With a threshold of 25-OHD Ն30 nmol/L but Ͻ50 nmol/L to define vitamin D insufficiency, in 33% of the 54 individuals with 25-OHD concentrations classified as insufficient by RIA, 25-OHD concentrations were normalized by CLIA (range: 53.0 -109.5 nmol/L).…”

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

“…It must be underlined that, as in our previous studies on the same topic (6,9,10,11,12), the blood samples used here were obtained in the morning (0730-0930 h) after an overnight fast. Indeed, the ULN for a second-generation PTH assay obtained in healthy persons sampled in a nonfasting state over a larger time span was higher than in our studies (34) (see discussion in reference (6)).…”

“…Excluding subjects with low 25OHD from a reference population for serum PTH reference values is strongly recommended in the two most recent guidelines on the diagnosis and management of asymptomatic PHPT (7,8). We have demonstrated in several studies that this lowers the serum PTH ULN by 20-35% depending on the assay (6,9,10,11,12).…”

Divergence in Classification of 25-Hydroxyvitamin D Status with Respect to Immunoassays

“…None of the samples was frozen and thawed repeatedly. Samples were assayed either in duplicate for RIA (3 ), or singly for CLIA (4 ), according to manufacturers' instructions. With the RIA method, the intraand interassay CVs were, respectively, Ͻ15.0% and Ͻ17.0% at a mean concentration of 9 nmol/L, Ͻ10.0% and Ͻ11.0% at a mean concentration of 30 nmol/L, and Ͻ7.5% and Ͻ11.0% at a mean concentration of 150 nmol/L.…”