Parathyroid hormone using second and third generation assays in patients with various stages of chronic kidney disease.

Mineral metabolism disturbances are common in chronic kidney disease (CKD) and parathyroid hormone (PTH) plays an important role in patient monitoring. Levels of PTH may vary with different biochemical assays, especially with kidney dysfunction, and more evidence is needed to substantiate the differences between second generation (2. gen) and third generation (3. gen) PTH immunoassays in this patient group. A cross-sectional study of 350 CKD patients (61% males) in the North Denmark Region. From April to September 2023, blood samples drawn for measurement of PTH as part of routine care in the Department of Nephrology, Aalborg University Hospital, were consecutively collected for measurement of PTH using different assays (2. gen., Atellica, Siemens Healthineers and 3. gen, Cobas 8000, Roche Diagnostics). Results were reported as the mean relative difference (RD): (2. gen PTH-3. gen PTH)/3. gen PTH. Overall, the 2. gen assay provided higher values of PTH as reflected by the median PTH (2. gen: 26.4 pmol/L; 3. gen 14.5 pmol/L) and the mean RD (82%). When stratified by CKD subgroup, the difference between the assays increased with decreasing kidney function (CKD1-3 (n = 19): mean RD 41%; CKD4 (n = 25): 66%; CKD5 (n = 93): 81%; dialysis (n = 186): 90%). PTH measured with 2. and 3. gen assays differed markedly among CKD patients, and the assay difference was dependent on the degree of kidney failure. Results inform clinical guidance on the monitoring and management based on PTH among patients with CKD.