Abstract: Background - Parathyroid hormone (PTH) measurement is sensitive to preanalytical handling. While refrigerated centrifugation (RC) is recommended, its availability is limited in many clinical settings. Hypothesis/Objectives - To assess the stability of canine PTH processed via adapted cooling centrifugation (ACC) and room temperature centrifugation (RTC) compared to RC. Animals - 18 client-owned dogs (9 healthy; 9 with IRIS CKD stages 2, 3 and 4). Methods - Samples were divided and mean temperatures (pre/post-centrifugation) were: RC (reference; 3.8/4.3°C), ACC (frozen water tubes; 12.2/20.7°C), and RTC (22.5/25.4°C). Serum PTH (1-84) was measured by modified immunoassay (DiaSorin S.p.A; sensitivity 4.0 pg/mL). Agreement was evaluated using Bland–Altman and Lin’s concordance correlation coefficient (CCC). Results - CKD dogs had higher phosphorus (p = 0.02), urea (p = 0.0003), creatinine (p = 0.0004), and PTH (p < 0.0001) than controls. No significant differences in PTH concentrations were detected between methods within groups (p = 0.9619). Both alternative methods showed high accuracy (> 0.90) and excellent concordance with RC: ACC (CCC 0.98; bias 0.200 pg/mL) and RTC (CCC 0.96; bias -0.122 pg/mL). Median PTH (pg/mL) for RC, ACC, and RTC were 6.6, 7.8, and 7.5 (healthy) and 26.0, 26.4, and 31.8 (CKD), respectively. Conclusions and Clinical Importance: Despite temperature increases during processing (up to 25.4°C in RTC), both ACC and RTC are effective for canine PTH measurement, provided samples are subsequently frozen. RC is not an absolute requirement for preanalytical stability.
