[Comparison of the intact PTH test with the total PTH test in hemodialyzed patients].

We measured PTH by intact PTH assays (iPTH) and whole PTH kit. iPTH includes 1-84 PTH (CAP) and the PTH antagonist fragment (CIP). The CAP/CIP ratio more precisely indicates the net relative actions of the agonist PTH (CAP) and the antagonist PTH fragment (CIP). The CAP/CIP ratio > 1 identifies patients with normal or high bone turnover disease, and the CAP/CIP ratio < 1 indicates patients with adynamic low bone turnover disease. Serum samples were obtained from 98 hemodialysis patients. We measured iPTH with intact PTH assay (PTH, intact Elecsys Systeme, Roche), and whole PTH with Duo PTH Assay (Scantibodies Laboratories, Santee, CA, USA), which determine human whole PTH or Cyclase Activating PTH (CAP) as well as total immunoreactive PTH (the sum of 1-84PTH and N truncated PTH fragments). Cyclase inactive PTH (CIP) is an inactive fragment 7-84 PTH and is calculated as total PTH--CAP. For the evaluation of bone turnover, the activity of serum alkaline phosphatase (AP) was determined by the method standardized according to IFCC. The adenosine monophosphate (AMP) buffer, reagents by LEK (Boehringer), and the Technicon RA-XT device were used. Mean intact PTH = 578 +/- 767 pg/ml; CAP = 332 +/- 366 pg/ml; total PTH = 518 +/- 560 pg/ml; mean AP = 1.9 + 2.9 mukat/l; CAP/CIP ratio < 1 was found in 9 patients. Mean CAP in these patients was 71 +/- 42 pg/ml; total PTH = 172.6 +/- 104.8 and intact PTH = 150 +/- 65 pg/ml; AP = 0.8 +/- 0.2 mukat/l. It is known that patients with adynamic bone disease have intact PTH below 200 pg/ml, and our next step will be to evaluate with bone biopsy whether patients with CAP/CIP ratio actually have adynamic bone disease.