Real-World Distribution of NT-proBNP and Its Association with Age and Cardiovascular Disease in an Iranian Tertiary Hospital

Heart disease remains the leading cause of death worldwide, a silent threat that often strikes before obvious symptoms appear. To catch these problems early, doctors rely on specific chemical signals in the blood that act as distress flares from the heart. One of the most important of these signals is a substance called NT-proBNP. This molecule is released when the heart muscle is stretched or under too much pressure, much like a rubber band snapping back after being pulled too tight. When the heart struggles to pump blood effectively, as happens in heart failure or other serious conditions, it produces more of this substance. Because of this, measuring NT-proBNP has become a standard way for doctors to diagnose heart trouble and decide on treatment. However, the levels of this chemical in a healthy person are not fixed; they shift based on a person's age, sex, and overall health. This makes interpreting the test results tricky, as a number that looks alarming for a young person might be normal for an elderly one. Without clear guidelines tailored to specific populations, doctors can sometimes misjudge a patient's condition, either missing a serious problem or worrying unnecessarily.

In a recent study conducted at a major hospital in Tehran, Iran, researchers set out to understand exactly how these levels behave in a real-world setting. They looked at 527 consecutive patients who had their blood tested for NT-proBNP as part of their routine medical care between March and August 2025. The team, led by scientists from Shahid Beheshti University of Medical Sciences, wanted to see if the levels of this heart marker were driven more by the patient's age, their sex, or whether they already had a known heart condition. Unlike studies that focus only on perfectly healthy volunteers, this research examined people who were already in the hospital, reflecting the complex mix of patients doctors see every day. The researchers measured the blood samples using a standard, automated machine and then sorted the patients into groups based on whether they had a documented history of heart disease and how old they were.

The results painted a clear picture of what influences these heart markers. The most significant finding was that patients with a confirmed history of cardiovascular disease had much higher levels of the substance than those without. The median level for patients with heart disease was 2,749 pg/mL, compared to 535 pg/mL for those without a known heart condition. This substantial difference confirms that the test is effective at identifying those with underlying heart stress. However, the study also revealed that age plays a massive role, independent of whether a person has a diagnosed heart condition. As patients got older, their levels of the substance rose steadily. The youngest group, those under 50 years old, had the lowest levels. The middle group, aged 50 to 75, showed higher levels, and the oldest group, those over 75, had the highest levels of all. The difference between the youngest and oldest groups was statistically significant, suggesting that the simple act of aging causes the heart to release more of this marker, even in the absence of a specific disease diagnosis.

Surprisingly, the study found no significant difference between men and women. While some previous research in other parts of the world suggested that women might naturally have higher levels of this heart marker, the data from this Iranian hospital showed that men and women had very similar levels. The researchers noted that in their group of patients, the presence of heart disease seemed to overshadow any natural biological differences between the sexes. This suggests that for this specific population, knowing a patient's age and whether they have heart disease is far more useful for interpreting the test than knowing their sex. The overall median level for all patients in the study was 659 pg/mL, a figure that is notably higher than what is seen in healthy community populations in other countries. The researchers attribute this to the fact that their study took place in a tertiary hospital, where patients are generally sicker and older than the average person in the community.

These findings offer a practical guide for doctors working in similar settings. The study reinforces the idea that there is no single "normal" number for NT-proBNP that applies to everyone. Instead, a high reading in an elderly patient might reflect the natural changes of aging, while the same reading in a younger person could signal a serious problem. The research highlights the need for doctors to look at the whole patient—their age, their medical history, and their current symptoms—rather than relying on a universal cutoff value. By providing this local data from an Iranian hospital, the study helps fill a gap in medical knowledge, offering a foundation for creating reference values that are specific to the local population. This ensures that when a doctor sees a test result, they can interpret it with greater accuracy, leading to better care for patients who are already navigating the complexities of hospital treatment.