Here’s why you shouldn’t panic if you learn an elderly loved-one’s D-dimer test came back positive and indicates a blood clot.
The D-dimer blood test is to screen for a blood clot, and doctors routinely order this test when a patient presents to an ER with symptoms that a blood clot in the lung can cause. I learned this firsthand with my mother’s ER visits.
A D-dimer result is more likely to be a false-positive in a person over age 50.
That’s potentially a lot of CT scans (the standard follow-up to a positive D-dimer) and hence, a lot of unneeded radiation, for all those false-positive results.
What is a pulmonary embolism?
“A pulmonary embolism occurs when an artery in the lungs becomes blocked by something that travels through the circulatory system and lodges in the lung,” explains Christopher J. Hanifin, PA-C, who was previously a physician assistant in open heart surgery with Cardiothoracic Surgery of South Bend in South Bend, IN.
“The most common culprit is a blood clot that forms in a large vein in the leg – a deep vein thrombosis – and then breaks loose and is carried to the lungs,” continues Hanifin.
“Depending upon the amount of lung involved, this is usually associated with some degree of shortness of breath.
“PE is also commonly associated with chest pain, which can be vague and difficult to distinguish from other causes of chest pain.”
Even if you go to the ER with ONLY chest pain, you’ll get a D-dimer test — which is done from a blood sample.
It makes sense that older age is included in the screening, as was in a study that appears in the March 19, 2014 issue of JAMA.
Age of the Patient
The report in JAMA says that using a person’s age to raise up the threshold for an abnormal D-dimer result appeared to be safe, and it led to fewer healthy people getting a diagnosis of a pulmonary embolus.
A blood clot causes a breakdown product called D-dimer.
A negative blood result means you don’t have a pulmonary embolism. But with increasing age comes an increased likelihood of a positive result, even if there are no blood clots.
This makes the test less reliable for elderly patients when compared to younger.
Dr. Marc Righini’s study redefined the test value by multiplying the participant’s age by 10 if the patient was at least 50, and using this numerical result with the blood test result.
The team was able to safely exclude a pulmonary embolus diagnosis in elderly patients who were suspected of having a PE.
Over 3,300 participants with suspected PE were involved.
When a patient’s age with a multiplication by 10 was factored into the blood test result, the PE diagnosis was safely excluded.
Some years ago while at the health club, minutes before I was scheduled to train my next client, I called my father to see how my mother was doing, as he had taken her to the emergency room because she was having shooting pains in her upper abdomen.
He told me that the doctor suspected a blood clot in her lung.
This scared the willies out of me and I had difficulty pretending everything was alright while I trained my bubbly client.
“A laboratory test – the D-dimer – can also suggest the presence of a clot in the body, but this test becomes less reliable in older patients,” says Hanifin.
Too bad I hadn’t known, at the time, that being over age 65, in and of itself, can yield a positive D-dimer result in the absence of a blood clot.
Turned out my mother’s lungs were just fine.
Several years later, my mother would end up having at least three more emergency room D-dimer tests, all coming back positive! (Again, lungs just fine each time.)
The second time my mother’s D-dimer was positive, I didn’t have the fear that I’d had several years prior at the gym.
That’s because I knew that it would probably be another false-positive (and it was).
The third time the D-dimer was positive? I thought, “Here we go again, another CT scan and unnecessary radiation.”
Hanifin explains, “A patient presenting with chest pain or shortness of breath with risk factors for PE should generally have a CT scan performed.
“A CT scan can usually identify the presence and extent of any clots fairly reliably.
“A further benefit of the CT scan is that it can often identify other pathology in the event a PE is not the cause of the symptoms.”
The fourth time the D-dimer was positive, my mother was deemed unsuitable for the CT scan due to mild kidney dysfunction, so she was advised to have a “VQ” scan of her lungs.
Chest pain and difficulty breathing can have many causes.
My mother’s fourth D-dimer test was ordered because she complained of trouble breathing (which later was determined by a pulmonologist to be from panic attacks).