Thursday, March 30, 2006

False positive?

34 Y/O F who presented to the ER with a week long history of progressive dyspnea. She complained of DOE with moderate activities and intermittent SOB at rest. No other associated Sx. She is otherwise healthy.

Mild asthma

No allergies or medications

SH: No exposures, no drugs, non-smoker, no recent travel, immobility

FH: sister with asthma o/w (-)

Her vitals were normal, sat 97% on RA. Physical exam, ECG and CXR were normal. She has no risk factors for PE, and her Wells score was 0.

A V/Q scan was done in the ER with preliminary report of intermediate probability. She was started on heparin, admitted, and LE dopplers and CT-angiogram were ordered. D-dimer was not obtained.

The following day the final report on the V/Q scan was changed to low probability, LE dopplers were (-), and the CT-angiogram showed a filling defect in a LUL sub-segmental artery suspicious for PE.

Her inpatient team started her on Advair and discussed the options of angiogram and anticoagulation with her. The feeling was that she is low risk for a PE and that the CT-angio is likely a false (+) and she decided not to have an angiogram or start coumadin, and she was discharged home.

She now presents to clinic with continued symptoms of dyspnea, no new symptoms, and a normal exam.
Spiro shows a very mild obstructive defect with normal FEV1.

How would you proceed from here?

How long after a PE would you expect to find an abnormality on angiogram?

5 comments - CLICK HERE to read & add your own!:

Jennings said...

Because her symptoms of dyspnea are not changed and she has obstructive physiology on PFT's, I think the dyspnea is more likely related to the underlying asthma. I would obtain an exercise test (with post-exercise spirometry)to more definitively identify asthma as the cause of the DOE. I would then be more satisfied about the previous CT being a false positive.

Mike L said...

Do you have a DLCO?
Where was the matched defect in the V/Q Scan?

I think I agree with Jennings... CPET with pre and post spirometry.

If the V/Q is matched in the LUL, I would probably push more for the angiogram.

Can anyone tell me the contrast difference between a CT angio and a PA-gram?

DKeena said...

On the V/Q scan there was a small matched defect in the LUL which corresponded to the abnormality on the PE-CT.

She has not had a DLCO yet.

What do you think her overall risk for having a PE is?

Without the CT- according to PIOPED it's 4%-- but CT angio is reported to have a specificity around 90%. The specificity probably lower for subsegmental PE's...

Baleeiro said...

An additional option is to repeat the V/Q and the dopplers. Serial scanning does increase your negative predictive value and may help settle the PE issue (Arch Intern Med 1994 Feb 14;154(3):289-97) without a PAgram.

Jennings said...

"What do you think her overall risk for having a PE is?"

There is no concensus on the "best" clinical prediciton rules, but as you cited, her Wells score for PE (Ann Emerg Med 2003, 42:266) was 0. Importantly (and part of the wells score actually) is that she has anotehr more likely disease to account for the symptoms (exercise-induced asthma). Additionally, her V/q was read as low prob. Therefore, the filling defect on the CT was likely a false positive related to the contrast bolus.
Again, I would do the CPET with spiro to confirm exercise-induced asthma and be satisfied with that diagnosis.