Evaluation of Reference Intervals for Serum Parathyroid Hormone in Korean Adults

Establishing assay-specific reference intervals for parathyroid hormone (PTH) is essential for appropriate clinical interpretation. However, data on PTH reference intervals in Korean adults using the Roche Elecsys assay are limited.

We retrospectively analyzed data from Korean adults who underwent simultaneous measurement of PTH and related biochemical markers between January 2020 and December 2023. Reference intervals were estimated using CLSI EP28 non-parametric methods in the total cohort and in subgroups with normal biochemical parameters, with additional assessment of 25-hydroxyvitamin D [25(OH)D] status.

During the four-year study period, we analyzed results from 509 individuals (101 men and 408 women; median age, 44.4 years [IQR, 35.5 - 54.9]). The central 95% reference interval for serum PTH in all subjects was 16.7 - 64.2 pg/mL. Among 461 individuals with normal biochemical parameters, the interval was 17.3 - 61.8 pg/mL, and after exclusion of outliers (449 subjects), the final reference interval was 17.3 - 53.6 pg/mL (90% CI: lower limit, 16.3 - 18.0; upper limit, 51.8 - 57.7). No significant differences were observed by gender or age; therefore, partitioning was not required. PTH concentrations varied significantly by vitamin D status, with higher values in individuals with 25(OH)D < 20 ng/mL compared with those with sufficient levels (≥ 30 ng/mL, p < 0.001). The derived intervals were broadly consistent with the manufacturer-provided reference intervals, although the upper limit tended to be higher in vitamin D-deficient subjects.

This study verified Roche Elecsys PTH reference intervals in Korean adults using an indirect approach and confirmed the importance of considering vitamin D status for interpretation, providing practical guidance for clinical laboratories.