Parathyroid hormone reference intervals in adults using second- and third-generation assays

Area of Science:

• Clinical Biochemistry
• Analytical Chemistry
• Endocrinology

Background:

• Parathyroid hormone (PTH) assays are routine biochemical tests.
• Different generations of PTH assays (second- and third-generation) exist.
• Understanding assay-specific performance is vital for clinical practice.

Purpose of the Study:

• To compare PTH levels between second- and third-generation assays.
• To establish method-specific reference intervals for PTH assays.
• To inform clinical practice regarding PTH assay transitions.

Main Methods:

• Method comparison using Passing-Bablok regression analysis.
• Establishment of reference intervals using adult blood donor samples.
• Utilized third-generation (Cobas 8000, Roche Diagnostics) and second-generation (Atellica, Siemens; Alinity, Abbott) PTH assays.

Main Results:

• Third-generation assay showed lower PTH levels compared to second-generation assays, with varying differences based on concentration.
• Method-specific reference intervals were established: 1.8-8.5 pmol/L (Siemens), 2.4-10.9 pmol/L (Abbott), and 1.8-7.0 pmol/L (Roche).
• Samples with low 25-hydroxy-vitamin D (<50 nmol/L) were excluded from reference interval calculations.

Conclusions:

• Second- and third-generation PTH assays are not interchangeable.
• Laboratories must inform clinicians about assay changes.
• Method-specific reference ranges are essential for accurate PTH testing and patient care.