Diagnosis of venous thromboembolism
BMJ 2009; 339 doi: https://doi.org/10.1136/bmj.b2799 (Published 19 August 2009) Cite this as: BMJ 2009;339:b2799
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Dear Editor
It is very heartening to note Professor Pierre-Marie Roy`s editorial
comment about “assessing clinical probability first, then performing D-
dimer tests” in the diagnostic strategy for venous thromboembolism.
Over a hundred D-dimers requests are received in an average size
hospital laboratory every week, where very often the results are positive.
In most of these cases, it is not clear whether a clinical probability
score was assessed before the test has been requested and as such whether
the test was actually necessary in the first place. On the contrary, a
normal D-dimer is often used as a stand-alone test without enough
consideration given to the well-known clinical probability scores. This is
despite reports where even major pulmonary emboli were detected despite
normal D-dimer results, although clinical probability was moderate to high
[1]. Venous thromboembolism can also occur despite normal D-dimer if the
symptoms have been present for several days and if thrombi are small.
Different laboratories use different assays and different cut-off points
for the upper limit of normal, which can also cause difficulties with
interpreting normal D-dimer results [2]. Hence, it is of utmost importance
to examine the patient and assess the chances of thromboembolism using one
of the several established scoring systems (e.g.; Well`s score for deep
vein thrombosis or the revised Geneva score for pulmonary embolism),
before taking into account the results of the D-dimer tests.
1. Gibson NS, Sohne M, Gerdes VE, Nijkeuter M, Buller HR. The
importance of clinical probability assessment in interpreting a normal d-
dimer in patients with suspected pulmonary embolism. Chest. 2008; 134: 789
-93.
2. Jennings I, Woods TA, Kitchen DP, Kitchen S, Walker ID. Laboratory D-
dimer measurement: improved agreement between methods through calibration.
Thromb Haemost. 2007; 98: 1127-35.
Competing interests:
None declared
Competing interests: No competing interests
Running up Snowdon with venous thromboemboli
As someone who was admitted to hospital (quite by accident) with
multiple bilateral pulmonary emboli earlier this year, with emboli
demonstrated on CTPA in all the major pulmonary arteries, I would be in
favour of careful use of d-dimer tests at an earlier stage, even for
people who do not have classic symptoms of venous thromboembolism. My d-
dimer level on admission in April was 2628 mcgFEU/l and it was this
result, a five-month history of not being able to run quite as fast as
usual, a new onset right bundle branch block and prominent pulmonary
vasculature on x-ray that led to a CTPA being ordered to provide a
definitive diagnosis. I had presented to my GP about three months earlier
saying my half marathon times were down slightly and that I had found it
hard work doing the university running club's annual Christmas run up
Snowdon. I had been worried I might have become anaemic for some reason
and so was interested in having my haemoglobin level checked. I'd
certainly had no classic symptoms of pulmonary emboli and could not recall
at that time having anything that could be construed as a deep vein
thrombosis in the previous months. My Hb came back at 15.5g/dl, instantly
ruling out anaemia, and an ECG, peak flow and chest x-ray were all normal.
I presumed exhaustion from final-year exam preparation was to blame. I had
spoken to a number of doctors during my clinical attachments and all were
intrigued as to what might have been going on. Although improving
gradually, after a couple of months I returned to my GP and it was then
that I was referred to the hospital for some lung function tests. I was
admitted by chance before the appointment had come through following a
fortuitous meeting with one of the A&E consultants. Had it been routine to
measure d-dimer levels at the slightest hint of reduced exercise tolerance
I'm sure the results would have been so suggestive of clot involvement
that further investigation would have been warranted. Exercise tolerance
was improving at the time of admission (I had completed another half
marathon the month before), so I can only presume my d-dimer levels would
have been higher in the preceding months. After diagnosis, and whilst
trying to establish the cause in my own mind, I remembered that in October
2008 I had strained a calf muscle whilst running and awoken with cramp one
morning a day or two later. I believe a small muscle knot, present for a
few days, may have clamped a vein causing an asymptomatic calf vein
thrombosis, which was the source of the emboli. I had forgotten all about
this when I visited the GP a few months later. Had there been laboratory
proof to hand that there were circulating breakdown products of blood
clots I might have remembered what had happened 2-3 months earlier. The
clinical picture, aided by a d-dimer result, would then have been more
complete and further appropriate investigations then considered. Of
course, mine may be a unique presentation, but I can't help feeling that
my treatment may have begun several months earlier if
d-dimer levels were assessed more routinely. As with many diagnostic tests
in medicine they can be a useful tool if used appropriately.
Competing interests:
None declared
Competing interests: No competing interests