NT-proBNP

Where it comes from

Made in

Ventricular heart muscle, one for every BNP

Sent out by

With BNP, on stretch of the ventricle

Acts on

• None

What it does

• No action in the body: it is the off-cut, kept because it is easy to measure
• Lasts an hour or two in blood where BNP lasts twenty minutes
• Leaves through the kidney, so it climbs in kidney failure

In medicine

• The most used heart failure test: below 125 pg/mL at rest, or 300 pg/mL in an emergency, heart failure is unlikely ¹
• Age and kidney function raise it; obesity lowers it ⁴
• Unaffected by sacubitril, so it is the test for patients on sacubitril/valsartan ³
• Used to time treatment in asymptomatic aortic stenosis and to screen for heart damage during cancer treatment

Beyond the body’s own use

• The thresholds move with the patient. Below 300 pg/mL acute heart failure is effectively excluded, with a negative predictive value of 98%, while the rule-in cut-off climbs with age: 450 pg/mL under 50, 900 to 75, and 1,800 above that ¹
• Kidney failure raises it because the kidney clears it, and obesity lowers it: in 2,707 people a higher body mass index went with lower NT-proBNP as well as lower BNP ⁴
• Neprilysin does not break it down, so sacubitril/valsartan leaves it usable while BNP rises; that is the single practical reason the two tests are not interchangeable ³
• Treating the number rather than the patient has been tried and failed: 894 patients with heart failure were randomised to titrate therapy towards an NT-proBNP under 1,000 pg/mL, and the trial was stopped for futility ²