Reference intervals and decision limits for B-type natriuretic peptide (BNP) and its precursor (Nt-proBNP) in the elderly

Background: Elderly patients have the highest prevalence of heart failure (HF). The aims of the study were to establish a reference interval for B-type natriuretic peptide (BNP) and (Nt-proBNP) in elderly people, and to identify clinically relevant decision limits based on long-term outcome. Methods: Plasma concentrations of BNP and Nt-proBNP were measured from two elderly populations: 218 healthy subjects (mean age 73 years, population I), and 474 patients (mean age 73 years, population II) with symptoms associated with HF. Study population II was followed for 6 years with registration of all cardiovascular mortality. Results: An association between both BNP and Nt-proBNP concentrations and age was found. The upper limit for the reference intervals in the healthy elderly (population I) was: BNP <= 28 pmol/L (<= 97 ng/L), and Nt-proBNP <= 64 pmol/L (<= 540 ng/L). Based on cardiovascular mortality, decision limits for BNP (similar to 50 pmol/L, similar to 170 ng/L) and Nt-proBNP (similar to 200 pmol/L, similar to 1700 ng/L) (population II) were determined. Conclusions: Besides establishing reference intervals for BNP and Nt-proBNP in an elderly population, a higher clinically relevant decision limit for BNP and Nt-proBNP was identified, indicating additive prognostic information of the peptides on top of measurements by echocardiography. Therefore, both reference intervals and decision limits should be included in clinical practice. (c) 2007 Published by Elsevier B.V.