Age-Adjusted D-dimer Calculator

Created by Łucja Zaborowska, MD, PhD candidate
Reviewed by Bogna Szyk and Jack Bowater
Last updated: Feb 15, 2022

The age-adjusted D-dimer calculator helps you calculate the D-dimers cutoff level for your age. Lower D-dimers may be helpful in ruling out a Pulmonary Embolism (PE) or Deep Vein Thrombosis (DVT) diagnosis.

This calculator is suitable for people who are at least 51 years old. There are different methods of calculating the D-dimer cutoff level and diagnosing PE if you are younger or pregnant.

What is a D-dimer test?

The D-dimer test is a simple blood test that measures the level of D-dimers present. It is usually performed on patients with mild symptoms to rule out Deep Vein Thrombosis or Pulmonary Embolism. Physicians generally don't use it to confirm one of these conditions, since many other diseases or physiological states may also increase the number of D-dimers circulating in the bloodstream. The D-dimer test is frequently used with many different tools to calculate the probability of Pulmonary Embolism: for example the Revised Geneva Score or the Wells Rule (check the Pulmonary Embolism (PE) diagnosis section below).

How to calculate D-dimer levels?

In order to use the Age-Adjusted D-dimer calculator, you need the following data:

  • Age (>50 years old).
  • D-dimer unit type used in your laboratory.

There are two main types of D-dimer unit:

  • FEU - Fibrinogen Equivalent Units (more common, basic cutoff: 500 µg/L)
  • DDU - D-dimer Units (basic cutoff: 250 µg/L)

They have the following multipliers:

  • FEU : 10
  • DDU : 5

The equation for calculating age-adjusted D-dimer:

D-dimer cutoff = Age * (Unit type multiplier)

If your D-dimer level is below the calculated threshold, your doctor can rule out the diagnosis of Deep Vein Thrombosis or Pulmonary Embolism. If your levels are higher, you may be at risk of developing one of those severe conditions.

Keep in mind that many other diseases or physiological states can elevate the amount of D-dimers.

Why do I have elevated D-dimer levels?

The process of coagulation ends up with the creation of fibrin - that's when the bleeding stops. If the coagulation lasts for too long or is too excessive, the organism tries to break down the fibrin. Those small particles created in the process are called the D-dimers.

That's why measuring D-dimers is so essential - it's the best way to evaluate the presence of pathological forms of clotting, like embolus or thrombus.

If you want to go deeper, here's the CHA2DS2-Vasc calculator to assess the risk of stroke and other thromboembolic complications. You may also check the warfarin dosing to get to know something more about the possible treatment.

What is the Deep Vein Thrombosis?

Deep Vein Thrombosis is a process of forming clots in deep veins of our body. The thrombus usually forms in one of our legs, but it may travel all around the cardiovascular system. If it's big enough, it may clog one of essential arteries. The disease is more common among people who are immobilized, heavily treated or suffer from inherited coagulation defects.

The signs of DVT include:

  • pain, tenderness in affected area
  • oedema
  • reddened skin in affected area
  • fever or elevated temperature

Deep Vein Thrombosis (DVT) diagnosis

Elevated D-dimers might be a sign of a Deep Vein Thrombosis process. A physician may suspect DVT if there's a correlation between laboratory test findings, reported symptoms, and the state of the patient. A diagnosis of DVT can be made only after performing a compression ultrasonography test to confirm the presence of clots in the patient's veins. Lower limbs are the most common location of the thrombus. The leg involved in a pathological process is usually swollen, tender, painful, and reddened.

DVT may progress to a more severe condition such as Pulmonary Embolism. In sporadic cases with unfavorable anatomy, it may even result in a stroke.

Pulmonary Embolism (PE) diagnosis

Elevated D-dimers may indicate a Pulmonary Embolism.
It is a serious life-threatening condition. PE happens when loose clots formed in veins travel to lungs and clog up pulmonary arteries, creating an embolus. The bigger the clogged artery is, the more severe and urgent is the patient's condition. The most common symptoms of PE are shortness of breath, chest pain, coughing up blood, or reddened foamy sputum.

To calculate the probability of PE, we can use many different methods: Revised Geneva Score calculator, or the Wells Rule calculator. Your doctor will need the CT scan to confirm the diagnosis. Low levels of D-dimers may be helpful to rule it out.

PS Have you ever wondered how big is your lung capacity?

Łucja Zaborowska, MD, PhD candidate
Age
years
D-dimer unit type
FEU
D-dimer cutoff value
µg/mL
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