Introduction: Who Should Undergo Diagnostics

If you suddenly experience shortness of breath, chest pain that worsens with deep breathing, or feel lightheaded or faint, you need medical attention right away. These symptoms could signal a pulmonary embolism, which is a blood clot that blocks an artery in your lungs. This condition is a medical emergency that demands immediate diagnosis and treatment.^[1]

Pulmonary embolism can be difficult to identify because its symptoms often resemble those of other heart or lung conditions. Some people may experience sudden, severe symptoms within seconds or minutes, while others notice milder signs that develop gradually over days or even weeks. Because about 33% of people with pulmonary embolism die before receiving a diagnosis and treatment, seeking medical care at the first sign of trouble is critical.^[2]

You should seek diagnostic testing immediately if you have any combination of the following symptoms: sudden breathlessness (whether you’ve been active or at rest), sharp chest pain that gets worse when you cough or take a deep breath, rapid breathing, fast heartbeat, coughing up blood, pale or bluish skin, excessive sweating, or feelings of anxiety with lightheadedness.^[1][2]

Certain people are at higher risk and should be especially alert to symptoms. If you’ve had surgery recently, especially joint replacement, if you’ve been on bed rest for an extended period, if you have cancer, heart disease, or a broken bone, or if you take hormone-based medications like birth control pills, you face increased risk. Pregnant women and those who have recently given birth also need to be vigilant, as the risk is highest for about six weeks after childbirth. Long periods without movement, such as during lengthy flights or car trips, can also increase your risk.^[5][2]

Diagnostic Methods

Diagnosing pulmonary embolism can be challenging because the condition shares symptoms with many other heart and lung problems. This is why doctors use a combination of medical history, physical examination, and several different tests to confirm whether you have this condition.^[8]

Initial Assessment and Clinical Scoring

When you arrive at the hospital with symptoms that might suggest pulmonary embolism, doctors first assess how likely it is that you actually have this condition. They use standardized tools called clinical scoring systems such as the Wells criteria and Geneva score. These systems consider your symptoms, risk factors, and physical examination findings to calculate the probability that you have a pulmonary embolism. This probability assessment helps determine which diagnostic tests you need next.^[9]

Your doctor will ask about your medical history, including whether you’ve had blood clots before, recent surgeries, long periods of immobility, cancer, or other conditions that increase clotting risk. They’ll also perform a physical examination, checking your breathing, heart rate, blood pressure, and looking for signs like swelling, redness, warmth, or pain in your legs, which could indicate deep vein thrombosis (a blood clot in your leg that can travel to your lungs).^[6][7]

Blood Tests

If your risk level appears low to moderate based on the initial assessment, your doctor will likely order a blood test called a D-dimer test. D-dimer is a substance that your body produces when it breaks down blood clots. If this test shows low levels of D-dimer, it can rule out pulmonary embolism, meaning you probably don’t have this condition and won’t need further testing. However, high D-dimer levels don’t necessarily confirm pulmonary embolism because many other conditions can also raise these levels.^[4][6]

Your healthcare team may also check your blood oxygen and carbon dioxide levels through an arterial blood gas test. A clot in your lung can lower the oxygen in your blood. Additionally, doctors sometimes measure levels of substances called troponin and brain natriuretic peptide, which can indicate whether your heart is under strain from the pulmonary embolism.^[8][9]

Imaging Tests

CT pulmonary angiography (CTPA) is the main test used to diagnose pulmonary embolism. This imaging test takes detailed pictures of the blood vessels in your lungs and can clearly show whether blood clots are blocking any of these vessels. During this procedure, you lie on a table that moves through a CT scanner while X-rays are taken from different angles. A special dye is usually injected into your vein to make the blood vessels show up more clearly on the images. This test is highly accurate and is the standard way to confirm pulmonary embolism.^[6][8]

If CT scanning isn’t available or suitable for you, doctors may use a ventilation-perfusion scan (also called a V-Q scan). This test involves two parts: one measures air flow in your lungs (ventilation) and the other measures blood flow (perfusion). The test uses small amounts of radioactive material to create images. If areas of your lung have good air flow but poor blood flow, this suggests a pulmonary embolism might be blocking blood vessels in those areas.^[8]

Ultrasound of your legs, specifically duplex ultrasonography or compression ultrasonography, uses sound waves to check for blood clots in the deep veins of your legs. A wand-shaped device called a transducer is moved over your skin, creating moving images of your veins. If doctors find clots in your legs, they know these could travel to your lungs and cause pulmonary embolism. This test is noninvasive and painless. Finding clots in your legs doesn’t confirm pulmonary embolism, but their absence makes it less likely.^[8]

Other Diagnostic Tests

A chest X-ray cannot diagnose pulmonary embolism and may even appear normal when you have this condition. However, doctors often order this test to rule out other conditions with similar symptoms, such as pneumonia or a collapsed lung.^[8]

An electrocardiogram (EKG or ECG) measures the electrical activity of your heart. While it cannot directly show pulmonary embolism, it can reveal patterns suggesting that your heart is under strain, which happens when large clots block blood flow to your lungs. This test can also help doctors rule out a heart attack, which can cause similar symptoms.^[9]

In some cases, doctors may perform an echocardiogram, which is an ultrasound of your heart. This test can show whether the right side of your heart is working harder than normal or showing signs of strain, which can occur with pulmonary embolism. This test is particularly useful for patients who are too unstable to be moved to a CT scanner.^[9]

In rare situations where other tests are inconclusive and pulmonary embolism is strongly suspected, doctors may perform pulmonary angiography. This involves threading a thin, flexible tube (catheter) through your blood vessels to your lungs while injecting dye and taking X-ray images. This test is very accurate but is invasive and carries more risks than other imaging methods, so it’s rarely used now that CT technology has improved.^[8]

Diagnostics for Clinical Trial Qualification

Clinical trials studying new treatments for pulmonary embolism use standardized diagnostic criteria to ensure all enrolled patients truly have this condition. These trials typically require confirmation through CT pulmonary angiography, as this is considered the gold standard for diagnosis.^[8]

Many clinical trials use risk stratification systems to categorize patients based on the severity of their pulmonary embolism. These systems combine clinical scoring tools like the Wells criteria or Geneva score with imaging findings and blood test results. Researchers use biomarkers (measurable substances in your blood) such as troponin and brain natriuretic peptide levels to assess how much strain the pulmonary embolism is placing on your heart. This information helps determine whether patients qualify for specific treatment trials.^[9]

Clinical trials often include ultrasound examination of leg veins to document whether deep vein thrombosis is present alongside pulmonary embolism. This information helps researchers understand the complete picture of venous thromboembolism (the medical term that includes both deep vein thrombosis and pulmonary embolism). Some trials also require echocardiography to measure heart function and detect right ventricular strain, which indicates more severe cases.^[9]

Trials may exclude patients whose pulmonary embolism is too mild or too severe. For example, studies testing blood-thinning medications might only include patients with confirmed clots but without severe low blood pressure or shock. Conversely, trials testing aggressive treatments like clot-dissolving drugs might specifically enroll patients with massive pulmonary embolism who have unstable vital signs.^[12]