If you were experiencing feelings of dread, lightheadedness and sweating, would you think you were suffering from a blood clot in your lungs? Probably not, and as it turns out, plenty of doctors might not make the connection either. According to one study, pulmonary emboli is one the most commonly misdiagnosed conditions, and when left untreated, about 30 percent of those suffering from it will die.

While we hear a lot of news about drug errors and nightmarish incidents of surgery performed on the wrong body part, incorrect diagnoses are even more prevalent in the medical world. Missed, incorrect or delayed diagnoses are estimated to affect 10 to 20 percent of medical cases, oftentimes with serious consequences. One study found that of 583 diagnostic mistakes reported, 28 percent of them were life-threatening or resulted in permanent disability. By some accounts, there are at least 12 million misdiagnoses a year in the United States.

A 2008 meta-analysis of autopsy and malpractice data published in the Internet Journal of Family Practice looked at the outcomes of malpractice and autopsy findings to compare relative rates of misdiagnoses. The authors discovered that these diseases were the most commonly misdiagnosed:

1. Infections

The data showed that acute infections were the number one most commonly misdiagnosed condition, but that was based on the sheer number of cases. Since there are millions more infections than the other illnesses considered, that skews the numbers; if relative incidence is calculated, infections do not make the top five. That said, there are a lot of infections that are misdiagnosed, and they are often fatal.

2. Pulmonary emboli (blood clot in the lungs)

The symptoms of having a blood clot in the lungs — from unexplained shortness of breath and chest pain to anxiety and sweating — are often missed by health care professionals. And sometimes there are no signs or symptoms at all. The high rate of misdiagnosis for pulmonary emboli, the study suggested, could be an important factor in why the condition kills so many people each year. There are more deaths from pulmonary emboli each year (60,000-200,000) than from AIDS, lung cancer and car accidents combined.

3. Myocardial infarctions (heart attack)

Misdiagnosis of heart attack often happens when the patient is unable to accurately report symptoms or if the patient does not have common risk factors. In addition, heart attacks don’t always present as we might expect; the typical clutching, heaving, and collapsing we see on TV doesn’t always happen. (In fact, only 30 percent of women report having any chest pain at all during a heart attack.) To complicate matters, myocardial infarction symptoms can be easily confused with heartburn, pulmonary embolism, gallstones, bronchitis, gastritis or nervousness.

4. Cardiovascular disease

According to the Centers for Disease Control and Prevention, around 600,000 people die of heart disease in the United States every year; that’s one of every four deaths. A diagnosis of heart disease can be overlooked due to lack of symptoms, or because signs mimic those of other conditions. Symptoms like weakness, cough, fatigue, dizziness, backache, indigestion, sweating, shortness of breath, nausea and vomiting are often attributed to less serious conditions like anxiety, GERD, gallstones, muscle aches or influenza.

5. Neoplasms (cancer)

The study found that based on relative incidence, the five most commonly misdiagnosed diseases were breast cancer, melanoma, gynecological cancer, colorectal cancer and hematological cancer. The authors note that 12 percent of cancers are initially misdiagnosed.

In addition, the following conditions are also commonly missed or given the wrong diagnosis:

Misdiagnosed illnesses

Do you now the signs of stroke? (Photo: Lightspring/Shutterstock)

6. Stroke
Some stroke symptoms are obvious, but others are so slippery to catch that emergency room doctors often get the diagnosis wrong. A study from Johns Hopkins looked at 200,000 stroke patients and found that nearly 13 percent of them had visited the emergency room up to a month earlier with complaints of headaches and dizziness – indicating a stroke or a precursor – but were diagnosed with benign conditions like inner ear infection or migraine, or received no diagnosis at all. Further, doctors were up to 30 percent more likely to misdiagnose signs of stroke in women and minorities; the odds were even worse for those under the age of 45. The authors estimate that between 15,000 and 165,000 stroke cases each year are misdiagnosed.

7. Celiac disease

Although we seem to be a nation of people who love to shun wheat, those who suffer from celiac disease have an autoimmune disorder that makes them unable to digest gluten. The vomiting, abdominal pain and bloating, diarrhea, weight loss, anemia and leg cramps that can come with celiac disease are often attributed to other conditions, especially irritable bowel syndrome. While there are blood tests to measure for signature antibodies, some 10 percent of people with the disease nonetheless test negative. The National Institute of Diabetes and Digestive and Kidney Diseases says that many people with celiac go for more than a decade before a proper diagnosis is made.

8. Lupus

Listed by the AARP as one of the illnesses that doctors often have trouble identifying, the symptoms of this chronic inflammatory disease include fatigue, rash and joint pain; it can be misdiagnosed as chronic fatigue syndrome, fibromyalgia or rheumatoid arthritis.

9. Sacroiliac joint dysfunction (chronic lower back pain)

Studies show that 20 to 25 percent of chronic lower back pain comes from the sacroiliac joint — the joint that connects the spine and the pelvis — not the spine itself. Yet most spine specialists don't learn about this area during their residency or fellowships, and as a result, says CNN, “many people progress through the usual stages of back pain treatment, from physical therapy and chiropractic treatment to injections, laser procedures and finally to surgery, without ever addressing the true source of the pain.” One study found that for spinal fusion patients who still had chronic pain after surgery, the sacroiliac joint was to blame in more than half the cases.  

10. Parkinson's disease

There are no lab tests to diagnose this degenerative disorder of the central nervous system, but the tremors, stiff muscles, and balance problems are sometimes attributed to Alzheimer's, stroke, stress, traumatic head injury or essential tremor.

11. Lyme disease

Without evidence of having been bitten by a tick or the telltale bull’s-eye rash, many cases of this systemic infection are not diagnosed quickly. Symptoms that come with Lyme disease – such as shortness of breath, abdominal cramping, nausea, vomiting, and a stiff neck – may be diagnosed as mononucleosis, influenza, chronic fatigue syndrome, fibromyalgia or depression.

12. Depression

And speaking of depression, a 2009 meta-analysis of more than 50,000 patients found that general practitioners have a tough time distinguishing between those with and those without depression, and in fact, they made more misidentifications (false positives of depression) than the number of depressions they accurately diagnosed during initial consultations.

While the statistics may seem grim, the point is that as patients we need to be a bit proactive – and doing so can make a difference. Listen to your body and press on if you feel like your physician isn't getting something. Be clear about your symptoms and make sure your doctor knows your medical history. Ask your doctor for a differential diagnosis (a list of other diagnoses that are possible) and know that it's fine to second guess. Feel comfortable asking for tests and if you don't hear back with the results, follow up. And don't be afraid to ask for a second opinion. As Charles Cutler, MD, an internist and chair of the American College of Physicians' Board of Governors tells WebMD, "I'm not perfect, and to go to another doctor and get another opinion doesn't threaten me in any way." Nature, science, and biology are unpredictable, he says. "Good doctors are not threatened by a second opinion. In fact, they're strengthened by it."

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