If you are older, or perhaps have a blood clotting disorder or know someone who has, you likely have heard of DVT or deep vein thrombosis. Failing to diagnose DVT can have devastating consequences.

In most of us, most of the time, our blood flows freely through our arterial and venous systems, delivering oxygenated blood to organs and tissues, and taking back deoxygenated blood to the heart and lungs to be reoxygenated.

However, for a variety of reasons, sometimes blood can form clots. In the venous system, these can include clots in superficial veins (those closer to the skin) and the deep veins. When a clot forms in a deep vein (often in the leg), that can spell serious trouble for the patient. If it breaks off, it can flow up the deep vein to the lung and block blood from getting to the lung. This is called a pulmonary embolism, or PE.

A PE can kill you quickly.

Even if a DVT doesn’t cause a PE and kill you, it can cause other lung problems, and it can also cause post-thrombotic syndrome: chronic pain, swelling, and other symptoms in your leg. This condition can be permanent.

So, DVTs are a big deal. Fortunately, when they are properly diagnosed and treated, patients most often recover fully and are able to return to their previously normal lifestyle.

Unfortunately, failing to diagnose DVT happen too often, leading to otherwise preventable pain, suffering, and death.

How failing to diagnose DVT can happen

Medical providers working in emergency departments, urgent care clinics, and primary care offices must have a high index of suspicion for DVT, and particularly if a clot has already travelled up to the lungs and is causing breathing problems.

Symptoms of a DVT alone include pain in the leg, like cramping or soreness. The patient may also have red or discolored skin, swelling, or a feeling of warmth in the leg. However, it is also not uncommon for a DVT to cause no symptoms.

Often, however, the reason a patient goes to the ER is because they aren’t feeling well, and that can often mean a clot is causing more serious symptoms by blocking off blood flow to the lungs. Such symptoms can include shortness of breath, pleuritic pain (pain in the chest when inhaling or exhaling), and a cough, among other things.

Often there a risk factors doctors and other diagnosing providers (such as Physicians Assistants and ARNPs) know, such as age, a prior history of DVT, certain cancers, blood clotting disorders, or a recent event that may have caused the DVT, like a surgery or prolonged period of immobility (that’s why on flights you are encouraged to drink water and get up every hour to stretch your legs!).

When a patient’s signs, symptoms and history are suggestive of DVT or PE, doctors have many tools at their disposal to lead them to the correct diagnosis. Unfortunately, failing to diagnose DVT can occur when a doctor does not consider DVT in spite of the information available to him or her.

Failing to diagnose DVT can also occur when a doctor doesn’t use the tool available to him or her, or fails to use them accurately.

One such tool is a very simple rule called PERC (Pulmonary Embolism Rule-out Criteria). There are 8 questions in the PERC rule, including things like age, heart rate, and prior DVT history. Answer all 8 questions “NO”, and the doctor is done and can move on to other possible diagnoses. Simple calculators are available to anyone with an internet connection, and often doctors keep such tools available to them right on their smartphones.

However, answer any one of the PERC questions “YES”, and the doctor can order a very simple blood test called a d-dimer. The d-dimer test is really good for telling you that you don’t have a PE. If the d dimer test is negative, the doctor can feel confident that it is very unlikely you have a deadly PE.

But the d-dimer test isn’t very good at telling you if you have a PE. Actually, it’s right about 50% of the time. For that reason, the next step is ordering an imaging study (typically a CT angiogram), which is very good at diagnosing a PE. However, failing to diagnose DVT causing PE can also occur if the radiologist interpreting the images misses the clots on imaging.

Once the diagnosis is made, treatment has become so good that some patients are safe to be treated with medications (typically blood thinners) on an outpatient basis. Other patients get medicine or other treatments while admitted to the hospital.

Failing to diagnose DVT can have serious consequences, which is why doctors must be careful to not miss it.