Negative ddimer positive US for DVT

[erin682]

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Anybody run into this? I found out today about a patient I saw a few months ago that had come in for ro DVT. I don't remember her specifically but looking at my note she seemed low risk for DVT with a normal exam. Her only risk factors was one previous DVT a number of years ago and leg pain for 3 weeks. For whatever reason I chose to evaluate her with ddimer and not US. She had some other vague complaints includind chest pain, with normal vitals, so I was probably trying to evaluate low risk PE/DVT in one test. Ddimer came back totally normal so I discharged home with close follow-up with pcp. The patient went to another hospital the following day and had an US that showed a non-occlusive thrombus.

Thoughts?

 

[otacon88]

Doesn't hx of DVT and calf tenderness put you at a 4.5, which is considered intermediate risk for well's

 

[WilcoWorld]

A history of DVT and absence of an alternate diagnosis adds up to a wells of 4.5 (7.5 if you consider unilateral leg pain as "clinical signs and symptoms of a DVT"). This puts the patient in the "PE likely" group of the dichotomized Wells approach, and thus too high risk for a d-dimer.

PERC & d-dimer testing are only meant for people who are unlikely to have a PE/DVT, so I only use the d-dimer in people with a Wells of 4 or less. This approach was well supported by this prospective trial.

 

[erin682]

Good points. I had essentially given her a 1.5 because of lack of any signs of DVT. Totally normal exam without tenderness or leg swelling. She stated she had a knot behind her knee that hurt. I didn't really consider that a symptom of DVT.

 

[southerndoc]

It's quicker for me to get an ultrasound done than it is for the nurse/tech to draw a d-dimer and the lab to run it. I realize not every ED has access to 24/7 ultrasound, so I guess my practice would change if I were in a place such as that. (I love working in a busy ED.)

 

[BADMD]

I had a patient like this as a resident. I ordered the US and it was positive. Turns out he was on dilantin so I called the lab to do it as an add on. They did a D-Dimer instead and it was negative.

I had someone once tell me that after a week or two, a clot may stabilize enough give a negative D-Dimer. I have no idea where he got that I haven't really found much to support it (or negate it).

 

[spyderdoc]

I wonder if it was an old/white clot since it was non-occlusive?

 

[Khaos]

I read a study that stated that a d-dimer is positive from the release of clotting factors and such and this only occurs for the first few days of a clot. If someone comes in with a chronic dvt the d-dimer will be negative.

 

[Hamhock]

Are chronic/non-occlusive/white clots with negative D-dimer important in the ED?

...or, is oupt doc work-up/referral OK?

The data from Wells indicate "not important".

That is: one could argue a negative D-dimer with "semi-positive" ultrasound (old, non-occlusive, inactive DVT) is not emergent/urgent.

However, the OP indicated there was chest pain in the ROS; which, changes my thinking completely.

HH

 

[SLUser11]

I wonder if it was an old/white clot since it was non-occlusive?

Exactly. DVTs don't always completely resolve, and ultrasounds can be positive for a while afterwards. The ultrasound finding may not have represented an acute event.

Patients with a history of DVT can have lots of reasons for leg pain, including recurrent DVT. However, another big one is the resultant chronic venous insufficiency from the initial clot.

However, I have to say that if you are evaluating a patient with chest pain, leg pain, and a personal history of DVT, you should probably be more aggressive than simply ordering the D-Dimer. There's really nothing about your story that fits with "low risk for DVT."

 

[turkeyjerky]

Exactly. DVTs don't always completely resolve, and ultrasounds can be positive for a while afterwards. The ultrasound finding may not have represented an acute event.

Patients with a history of DVT can have lots of reasons for leg pain, including recurrent DVT. However, another big one is the resultant chronic venous insufficiency from the initial clot.

However, I have to say that if you are evaluating a patient with chest pain, leg pain, and a personal history of DVT, you should probably be more aggressive than simply ordering the D-Dimer. There's really nothing about your story that fits with "low risk for DVT."

Well, the personal hx of dvt gives 1 pt for dvt, 1.5 pts for PE according to well's criteria, both of which would qualify the patient as 'low-risk'. This is of course assuming the exam and clinical gestalt were low.

 

[deleted109597]

Well, the personal hx of dvt gives 1 pt for dvt, 1.5 pts for PE according to well's criteria, both of which would qualify the patient as 'low-risk'. This is of course assuming the exam and clinical gestalt were low.

Well's gives 1.5 for any type of clot. And if you're thinking of DVT or PE at all, then they usually aren't low risk. I have personally seen a large number of positive studies for clot and negative D-dimers, sufficient that if I think they have one, I scan, and if I don't, then I don't order a D-dimer because it is nearly useless.

Also, of note, this patient falls out of PERC for same reason, in that they have a history of DVT. With the chest pain, they likely needed some sort of pulmonary imaging, as the followup US really doesn't answer the question of why the chest pain.

 

[xaelia]

Also, of note, this patient falls out of PERC for same reason, in that they have a history of DVT. With the chest pain, they likely needed some sort of pulmonary imaging, as the followup US really doesn't answer the question of why the chest pain.

Falling out of PERC mandates nothing. The negative LR is useful (although, the patient who is PERC negative was already so low-risk they probably didn't need PERC applied to them) but the positive LR does nearly nothing to their pre-test probability.

There are plenty of reasons the patient of note may have needed imaging, but falling out of PERC isn't one.

 

[deleted109597]

There are plenty of reasons the patient of note may have needed imaging, but falling out of PERC isn't one.

I figured if we were talking about useless clinical decision instruments that are less accurate than clinician gestalt then we should include all of them.

I still want to know if the patient had a PE though.

 

[SLUser11]

I have personally seen a large number of positive studies for clot and negative D-dimers, sufficient that if I think they have one, I scan, and if I don't, then I don't order a D-dimer because it is nearly useless.

This confuses me a little bit. Have you really seen a lot of patients with an acute DVT/PE and a negative d-dimer? In my experience, that situation is pretty rare.

I've never felt D-dimer to be useless. In the emergency room setting, I think it would have utility for patients with low to moderate suspicion for DVT, since the negative predictive value is so good (? 90-95%). However, since I don't practice emergency medicine, I'm less familiar with modern protocols for ruling out DVT.

Is there newer literature that questions the utility of D-dimer? I have to admit I've been limiting my reading recently to butt journals and Entertainment Weekly...

 

[pinipig523]

Simple:

The pt was not low risk for a DVT.

Or

The DVT is old.