Week-to-Week Biological Variation in the N-terminal Prohormone of Brain Natriuretic Peptide in Hemodialysis Patients and Healthy Individuals

To the Editor: The concentration of the N-terminal prohormone of brain natriuretic peptide (NT-proBNP)1 is often increased in patients with a reduced renal function. The suggested diagnostic cutoffs in acute or subacute heart failure [e.g., 300 pg/mL (66 pmol/L) and 125 pg/mL (27 pmol/L), respectively] are therefore probably not applicable for hemodialysis (HD) patients. A better approach may be to diagnose patients according to changes from their baseline NT-proBNP concentrations. The changes in patients who experience a clinical event can be compared with the reference change value (RCV), which is based on the analytical CV (CVa) and the within-person biological variation (CVi). The within-person variation describes the natural fluctuations in the concentrations of constituents in a stable situation. This study reports the CVa, CVi, between-person biological variation (CVb), RCV, and index of individuality (II) in HD patients and healthy individuals. The Regional Committee for Medical and Health Research Ethics approved the study. Informed written consent was obtained from 17 clinically stable patients who had been treated with HD at least twice weekly for ≥2 months. The patients …