Pain in the legs could be a sign of a dangerous blood clot. But it's often not diagnosed and treated in time, U.S. health officials say. They have started a campaign to spread the word about this problem. A blood clot in the leg is called deep vein (or venous) thrombosis, or DVT. A clot can kill if it moves into the lungs. This is called a pulmonary embolism. Such clots kill about 100,000 Americans each year. The new campaign includes a report from the surgeon general and booklets aimed at both patients and doctors. The Associated Press wrote about it September 15.

What is the doctor's reaction?

Diagnosing blood clots has always been a challenge. The symptoms related to a blood clot in the leg (deep vein thrombosis, or DVT) are often not typical. This also occurs with blood clots that break off and travel to the lung (pulmonary emboli, or PE). Most patients with DVT or PE don't describe the classic symptoms that doctors learn in medical school.

Here's why it can be so hard to diagnose these problems. Let's start with DVT. The most common symptom is leg pain. However, most people with leg pain don't have a DVT. When there's pain in the back of the calf or in the thigh and new swelling of the leg, then it is time to consider the possibility. To complicate matters, many people with a DVT don't have a swollen leg.

It's the same story for PE. The classic symptoms are sudden shortness of breath and chest pain that hurts more when you take a deep breath. But more people with PE have shortness of breath that comes and goes.

The doctor may find some clues in a physical examination. But more often than not, the exam doesn't nail it down.

So you might ask: Why a big public campaign to heighten awareness of DVT and PE if this is such a diagnostic problem? Despite the challenge, there are proven strategies that greatly increase the chances of making a correct diagnosis without testing everybody who has new leg pain or shortness of breath. There's another important reason as well. Taking steps to prevent blood clots in certain high-risk settings substantially decreases the risk of DVT and PE.

What changes can I make now?

Be aware of what factors put you at higher risk of DVT and PE. I put these factors into two groups. The first group has a higher risk than the second group. This includes:

  • A history of ever having a DVT or PE in the past

  • An inherited blood problem that puts you at risk for DVT and PE

  • Recent surgery

  • Cancer (other than skin cancers) that may not be completely cured

  • Recent significant leg injury, especially if it prevents you from getting out of bed

  • A hospital stay of more than two days

  • Poorly controlled heart failure

  • Family history of DVT or PE

  • Pregnancy and the few months after delivery

The second group of factors increases your risk, but not as much as the first group:

  • Current use of female hormonal therapy, such as birth control pills, hormone patches and hormones used to treat menopause symptoms

  • Obesity

  • A very long plane ride or car trip

  • A past episode of unexplained leg pain and swelling that you never had evaluated

If you develop a leg ache that doesn't have an obvious explanation and also have one of the above risk factors, call your doctor for advice. If your leg is also swollen, your doctor will want to examine you. You may need further testing, such as an ultrasound of the legs, a blood test called a D-dimer or both.

Even if you don't have the above risk factors, new pain and swelling in one leg should always prompt a call to your doctor for advice.

Whenever you have new chest pain or shortness of breath, always call your doctor's office. Most often, your doctor will want you to be examined. Your doctor will then decide if the diagnosis of PE is highly unlikely.

A person with no risk factors, no leg pain or swelling, a normal physical exam and another explanation for the chest pain will seldom have a PE. If your doctor is still unsure, you may get more tests. They might include a measurement of your blood oxygen level, a D-dimer blood test, a chest X-ray, an electrocardiogram (ECG) and perhaps a CT scan of the chest.

What can I expect looking to the future?

This campaign will increase awareness of the symptoms of DVT and PE, and also the need for DVT prevention in hospitals. If you are ever admitted to a hospital, ask your nurse what is being done to prevent blood clots. Most patients will get a daily shot of a blood thinner. People who should not receive blood thinners can wear compression devices on their legs to prevent clots from forming.