First off, BNP (beta natriuretic peptide) is simply a marker of mycardial tissue stretch (from something like heart
failure). A BNP level of 500 for one
patient may mean that they are in florid, decompensated heart failure, while a BNP level of 2000 may mean another patient is doing quite well from their chronic heart failure. We don't use the isolated number for much of anything, other than the initial diagnosis/workup of heart failure. The overall trend of the BNP is more important.