Normal ranges are for populations
Lab reports usually come with a reference range. Your result is either inside it or flagged. For natriuretic peptides in someone who already has heart failure, that approach is close to useless. Almost everyone with established heart failure will be above the population range.
The more useful question is not "am I normal?" It is "am I at my normal?"
That is the concept this paper builds on, and I think it is the single most practical idea in it.
Wet and dry peptide levels
The authors borrow the wet and dry language from the Forrester profiles and apply it to the blood test.
A wet natriuretic peptide level is the one you have when you are overloaded with fluid: breathless, swollen, heading toward a hospital admission.
A dry level, which they also call the optivolaemic level, is the one you reach once you have been stabilised on tailored, optimised treatment. Optivolaemic just means the right amount of fluid in the system, not too much, not too little.
The paper states it plainly: if truly optimised, the dry natriuretic peptide levels are essential for clinical decision-making.
Why everyone's dry number is different
Your dry level is personal. The paper lists what moves it:
- Stage of the disease
- Age
- Weight
- Kidney function
- Whether the left, right or both sides of the heart are overloaded
- Low cardiac output
- Arrhythmias
- Damage to the heart muscle
So one person's stable NT-proBNP might be a few hundred. Another's might be a few thousand. Neither is automatically "bad". What matters is the movement away from that person's own baseline.
How this changes monitoring
Think about how useful that is.
If you know your dry level, then a rising number becomes an early warning. It can signal fluid building up before you feel any different. The paper describes elevated levels in both symptomatic and asymptomatic heart failure as a hallmark of volume expansion with an increased risk of getting worse.
That means a blood test can sometimes pick up trouble before the scales, the ankles or the breathlessness do.
The flow chart at the end of the paper builds this in directly. For patients in every profile, the final instruction is to use dry versus wet natriuretic peptide levels to further fine tune therapy.
A detail from the data
The paper includes a figure comparing median wet and optivolaemic levels of both BNP and NT-proBNP in a group of patients with reduced ejection fraction. The visual message is simple: the drop from wet to dry is large. Effective treatment brings the numbers down a long way.
The paper also states that effective decongestion and proper use of guideline therapy may be accompanied by a fall in natriuretic peptide levels, normalisation of filling pressures and possibly an improvement in cardiac output. The blood test, the scan and the patient all move in the same direction when treatment is working.
Clinical stability is not the full story
One sentence in this section is worth highlighting. The authors write that clinical stability "cannot disregard" the activation of neurohormonal systems reflected by raised BNP and NT-proBNP.
In other words, feeling fine does not mean the underlying fight has stopped. Someone can look and feel stable while their peptide levels quietly say the RAAS and sympathetic systems are still running hot. That is a theme Part 6 picks up in detail.
What to do with this
If you have heart failure, here is the practical version.
Ask what your dry level is. After a period of stability on your current treatment, ask your team what your natriuretic peptide level was at that point. That is your reference number.
Ask how often it is being checked. Some teams track it routinely, some only check it during a crisis. Knowing which approach your team uses is helpful.
Ask which test. BNP or NT-proBNP. Different scales, and if you are on sacubitril/valsartan, NT-proBNP is generally the one to follow, as explained in Part 3.
Keep your own record. Write down the number and the date each time you get a result. Patients who track their own values notice trends that can get lost between appointments, particularly if they see more than one clinician.
A dry number turns a generic lab result into a personal early warning system. It is one of the few places in heart failure management where the patient can hold a genuinely useful piece of the picture.
In Part 5 we move to the scan: how an ultrasound estimates pressures that used to require a catheter.
This series discusses a peer-reviewed clinical review. Nothing here is medical advice. Heart failure treatment should always be guided by your own cardiology team.
