[Preanalytical variability of parathyroid hormone measurement in dialysis patients; application to Elecsys 2010...

The working group PTH-Vitamin D of the SFBC recently underlined the great intertechnic variability of parathormone (PTH) assays. At the same time, the data of the literature showed an impact of the preanalytic stage, significant and variable according to the automat used. We worked on the automat Roche Elecsys. On quickly centrifuged and decanted samples, the small difference in results between serum and plasma EDTA (6%) is compatible with an indifferent use of the two samples for dialysed patients. The reputation of greater stability on plasma EDTA seems primarily based on studies after decantation of plasma. The extension to a non decanted sample, maintained on primary tube for deferred shipping to the laboratory would require verification. Concerning the serum, on tube with serum separator, after early centrifugation, we checked the stability of the PTH measurement for a delay lower than or equal to 4 hours. For an extrahospital structure of dialysis, in the conditions of an early and an on site centrifugation, this delay allows to defer the transport of the primary closed tube to the laboratory. Contrary to plasma EDTA, the serum also allows simultaneous measurements of other parameters used for the care of the dialysed patients.