Development of a scintillation proximity assay for high-throughput measurement of intact parathyroid hormone

A simple, high-throughput scintillation proximity assay (SPA) for parathyro id hormone (1-84) (PTH) has been developed. Fifteen commercially available N-terminal and six C-terminal anti-PTH antibodies were evaluated for detect ion of human PTH(1-84). Two C-terminal antibodies (CR10731M and 10-P55) gav e the most consistent results. Using one of these antibodies (10-P55), an a ssay was developed with a sensitivity of 4 pg/ml for human and rat PTH(1-84 ). Porcine PTH(1-84) was not detectable. The intra-assay and inter-assay co efficients of variation for a 467 pg/ml sample were 6.1 and 6.5%, respectiv ely, and for a 21 pg/ml sample, 6.2 and 4.4%. Human PTH(1-34), while not de tected in the assay, interfered with the detection of PTH(1-84), Smaller fr agments [for example, human PTH(3-34)] and a C-terminal PTH fragment [PTH(5 3-84)] did not interfere in the assay. The procedure gave 106-110% recovery of human PTH(1-84) spiked into samples. Immunoreactive PTH concentrations in serum of rats administered EGTA were determined by SPA and by a commerci ally available PTH immunoassay. There was a good correlation between the tw o assays with significant increases in serum immunoreactive PTH concentrati ons at 15 and 30 min after EGTA injection and a rapid decrease to baseline values by 60 min. The SPA gives a high-throughput method for simply and acc urately determining PTH(1-84) concentrations in serum. (C) 1998 Academic Pr ess.