Optimization of blood sampling strategy to avoid spurious PTH elevation in patients with forearm parathyroid...

Accurate monitoring of parathyroid hormone (PTH) is critical for assessing surgical outcomes in patients with stage 5 chronic kidney disease (CKD), yet preanalytical factors such as sampling location are often neglected. We report a 52-year-old male with CKD5 who underwent total parathyroidectomy with autotransplantation (TPTX+AT) in the right forearm and arteriovenous fistula (AVF) creation in the left forearm. Routine PTH measurement showed an extremely elevated level (>530 pmol/L) that was inconsistent with his stable clinical condition. PTH was measured using a fully automated chemiluminescence analyzer (Roche Cobas e801,a third-generation assay). Multisite comparative sampling revealed that blood drawn within 5 cm of the graft site caused spuriously high PTH levels, whereas samples collected at least 10 cm away (including lower limb veins) returned expected values (10.6-12.9 pmol/L) consistent with systemic PTH concentrations. These results suggest that venipuncture near the autograft may induce artificial PTH elevation via direct tissue injury or local hormone diffusion. In CKD5 patients who have undergone TPTX+AT with concurrent AVF construction, we recommend blood sampling from the lower limbs or at least 10 cm away from the parathyroid autograft site on the ipsilateral arm to ensure reliable PTH measurement. This case underscores the importance of implementing standardized phlebotomy protocols, staff training, and integrated clinical-laboratory collaboration to minimize preanalytical errors in this vulnerable patient population.