Preanalytical mystery: falsely elevated intact parathyroid hormone due to sampling from a grafted forearm

Spurious elevations in intact parathyroid hormone (iPTH) can lead to unnecessary interventions. We describe a dialysis patient who developed unexpectedly high iPTH concentrations months after total parathyroidectomy with forearm autotransplantation (TPTX-AT). Blood samples had been collected from the grafted forearm, resulting in falsely elevated iPTH values. Once the sample was collected from the non-grafted arm, iPTH concentrations normalized. This case highlights the importance of sampling site awareness in laboratory diagnostics and demonstrates how implementing a simple laboratory information system (LIS)-based protocol can prevent misinterpretation.