A feeling in the waters: diagnosis of heart failure using urinary natriuretic peptides

Plasma levels of brain natriuretic peptide (BNP) and N-terminal pro-BNP (N-BNP) are highly sensitive markers of ventricular dysfunction and/or hypertrophy and, in established disease, offer prognostic value and may be useful for guidance of therapy. Ng and co-workers report in this issue of Clinical Science that urinary levels of N-BNP may be as useful as plasma levels for the discrimination of patients with and without heart failure. This raises the potential for a relatively simple urine test that could be used for the diagnosis of heart failure. Roles in prognostication and the guidance of therapy may also be possible but, perhaps of most significance, measurement of urinary N-BNP may be applied to screening of patients at high risk of heart failure. The main limitations of the study were that the sample of heart failure patients comprised only 34 individuals with New York Heart Association functional Class IV and that the observed correlation between levels of urinary N-BNP and plasma creatinine seemed counter-intuitive. The latter issue needs clarification, as renal impairment is a frequent co-morbidity among patients with heart failure and will potentially confound any observed association between ventricular dysfunction and urinary N-BNP levels. Another caveat is that it is unclear if testing for urinary N-BNP can be cheaply and conveniently administered on a large scale. Nevertheless, this first demonstration of elevated N-BNP in the urine of patients with heart failure raises a number of exciting possibilities with regard to the management of patients with established or possible heart failure. Further investigation is required and eagerly awaited.