Systematic review and meta-analysis of strategies for the diagnosis of suspected pulmonary embolism
BMJ 2005; 331 doi: https://doi.org/10.1136/bmj.331.7511.259 (Published 28 July 2005) Cite this as: BMJ 2005;331:259
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Dear Sir
We would like to comment on the proposed imaging strategies for
excluding pulmonary embolism derived by Roy et al consequent on their meta
-analysis of the strategies for diagnosis of suspected pulmonary embolism
(PE) (1).
A recent systematic review of the clinical validity of a negative
computed tomography pulmonary angiography (CTPA) in patients with
suspected PE showed an overall negative likelihood ratio (NLR) after a
negative CTPA of 0.07 (95% confidence interval [CI], 0.05-0.11) and an
overall negative predictive value (NPV) of 99.4% (95% CI, 98.7%-99.9%)
(2). Recent advances in multidetector CT technology have improved
visualization of sub-segmental pulmonary vessels and multislice CTPA now
has comparable sensitivity to conventional pulmonary angiography (3).
Several outcome studies have demonstrated low morbidity and mortality in
patients not anti-coagulated following a negative CTPA (subsequent PE in
1.1% of patients at 3 months) (4, 5). The 3-month recurrence risk is
comparable to that following negative conventional pulmonary angiography
(0.9%) (6) or normal lung scintigraphy (0.5%) (7). Since the clinical
validity of using CTPA to rule out PE is similar to that of conventional
angiography and both techniques have comparable sensitivities there seems
no logic in subjecting patients with a diagnostic lung perfusion scan or
CTPA (normal or positive) to an additional invasive procedure because of a
disparity between the clinical probability and the imaging findings as the
authors advise.
Furthermore, pulmonary angiography is now infrequently performed and
few radiologists maintain expertise in the technique. For all these
reasons we believe the technique should have only a very limited role in
the evaluation of patients with suspected PE. Readers of this article may
be misled that their patients may still need conventional pulmonary
angiography for definite diagnosis despite evidence to the contrary.
Dr Andrew Scarsbrook (Specialist Registrar in Radiology)
Dr Fergus Gleeson (Consultant Thoracic Radiologist)
Department of Radiology, Churchill Hospital, Oxford, UK
References:
1: Roy PM, Colombet I, Durieux P, Chatellier G, Sors H, Meyer G.
Systematic review and meta-analysis of strategies for the diagnosis of
suspected pulmonary embolism. BMJ. 2005 Jul 30; 331: 259
2: Quiroz R, Kucher N, Zou KH, Kipfmueller F, Costello P, Goldhaber
SZ, Schoepf
UJ. Clinical validity of a negative computed tomography scan in patients
with
suspected pulmonary embolism: a systematic review. JAMA 2005 Apr 27;
293(16): 2012-2017
3: Baile EM, King GG, Muller NL, D'Yachkova Y, Coche EE, Pare PD,
Mayo JR. Spiral computed tomography is comparable to angiography for the
diagnosis of
pulmonary embolism. Am J Respir Crit Care Med 2000; 161: 1010-1015
4: Goodman LR, Lipchik RJ, Kuzo RS, Liu Y, McAuliffe TL, O'Brien DJ.
Subsequent pulmonary embolism: risk after a negative helical CT pulmonary
angiogram - prospective comparison with scintigraphy. Radiology 2000; 215:
535-542
5: Gottsater A, Berg A, Centergard J, Frennby B, Nirhov N, Nyman U.
Clinically suspected pulmonary embolism: is it safe to withhold
anticoagulation after a negative spiral CT? Eur Radiol 2001; 11: 65-72
6: Henry JW, Relyea B, Stein PD. Continuing risk of thromboemboli
among patients with normal pulmonary angiograms. Chest 1995; 107: 1375-
1378
7: Meyerovitz MF, Mannting F, Polak JF, Goldhaber SZ. Frequency of
pulmonary embolism in patients with low-probability lung scan and negative
lower extremity venous ultrasound. Chest 1999; 115: 980-982
Competing interests:
None declared
Competing interests: No competing interests
As an ex-angiographer and a chest radiologist I am simply amazed at
what is claimed by this review. We all now have to bow reverently to
evidence-based medicine but many things that are obviously huge advances
are not assessed in papers suitable for reviews like this. Pulmonary
angiography is not risky in trained hands, and it has never deserved its
reputation either as a dangerous procedure or as the gold standard in the
diagnosis of embolism. It is nothing like as good as state-of-the-art
multi-detector CT. No meta-analysis will change the reality of the
overwhelming conversion of the investigation of pulmonary embolism to CT
all over the world. UK departments with inadequate CT access and excess
capacity on their gamma cameras may take comfort from this analysis but
almost everyone else will continue to expand their use of CT for this
problem. Any radiologist with a decent CT scanner will show you numerous
unequivocal emboli in segmental vessels that don't occlude the vessel and
would not be seen on angiography, even if selective.
Competing interests:
None declared
Competing interests: No competing interests
The authors make the following statement-: "Pulmonary angiography is
a reference method and is supposed to rule in or rule out pulmonary
embolism for all values of clinical probability." This statement surely
cannot be evidence-based if it is merely a self-referential statement that
implies, without supportive scientific evidence, that pulmonary
angiography can rule-out pulmonary embolism for all values of clinical
probability. There is now substantial evidence that suggests that high-
resolution, multidetector CT scans are probably more accurate than
pulmonary angiograms, and it is presumptious to assert that a negative
high-resolution CT scan is a FN result if a subsequent pulmonary angiogram
is read as positive. How does one definitively establish whether the high-
resolution CT scan is a FN result or whether the pulmonary angiogram is a
FP result -- considering that there is a large interobserver variability
in many PA readings? I simply cannot understand the logic of the authors'
recommendation that a low probability PE-patient who has a positive CT
scan result should have a pulmonary angiogram. I also think that it is
rational to presume that pulmonary embolism has been reasonably excluded
if a high probability PE-patient has a negative high-resolution
multidetector CT scan if the scan is technically acceptable. There are a
number of clinical outcome studies that demonstrate a very low 3 month
likelihood of a subsequent thromboembolic event (<5%) if a high-
resolution multidetector CT scan is negative -- irrespective of the
pretest probability of PE. I think that many chest physicians and chest
radiologists now believe that pulmonary angiography is no longer required
if the PE diagnostic workup utilises a high-resolution multidetector CT
scan of acceptable technical quality.
Jeff Mann, MD.
Competing interests:
None declared
Competing interests: No competing interests
Systematic review and meta-analysis of strategies for the diagnosis pf suspected pulmonary embolism. BMJ 2005; 331:259 July
We welcome the efforts of Roy et al to evaluate and clarify
diagnostic strategies for pulmonary embolism, a problem that places a
heavy burden on acute imaging departments. We do not share their
conclusions and suggest that more recent evidence is changing current
clinical practice.
The recommendation that pulmonary angiography is warranted for patients
with PE identified on imaging with a low clinical probability and also for
those with negative imaging and high clinical probability is a situation
the majority of departments are not able to offer availability of
pulmonary angiography is scarce, even in the US. Decisions are generally
taken on a balance of imaging and clinical probability without recourse to
further complex imaging.
There is also a growing body of evidence that a negative CTPA,
particularly with multislice CT (1,2,3) is grounds for withholding
anticoagulation.
The lack of comment on CT venography (4) was disappointing. This has
become increasingly popular as a method of increasing the diagnostic yield
from a single test. This has become increasingly used particularly in the
US but also in the UK.
1. Perrier A, Roy PM, Sanchez O, Le Gal G, Meyer G, Gourdier AL,
Furber A, Revel MP, Howarth N, Davido A, Bounameaux H. Multidetector-row
computed tomography in suspected pulmonary embolism. N Engl J Med. 2005
Apr 28;352(17):1760-8.
2. Musset D, Parent F, Meyer G, Maitre S, Girard P, Leroyer C, Revel
MP, Carette MF, Laurent M, Charbonnier B, Laurent F, Mal H, Nonent M,
Lancar R, Grenier P, Simonneau G; Evaluation du Scanner Spirale dans
l'Embolie Pulmonaire study group.Diagnostic strategy for patients with
suspected pulmonary embolism: a prospective multicentre outcome study.
Lancet. 2002 Dec 14;360(9349):1914-20.
3. Donato AA, Scheirer JJ, Atwell MS, Gramp J, Duszak R Jr. Clinical
outcomes in patients with suspected acute pulmonary embolism and negative
helical computed tomographic results in whom anticoagulation was withheld.
Arch Intern Med. 2003 Sep 22;163(17):2033-8.
4. Swensen SJ, Sheedy PF 2nd, Ryu JH, Pickett DD, Schleck CD, Ilstrup
DM, Heit JA. Outcomes after withholding anticoagulation from patients with
suspected acute pulmonary embolism and negative computed tomographic
findings: a cohort study. Mayo Clin Proc. 2002 Feb;77(2):130-8.
4. Cham MD, Yankelevitz DF, Shaham D, Shah AA, Sherman L, Lewis A,
Rademaker J, Pearson G, Choi J, Wolff W, Prabhu PM, Galanski M, Clark RA,
Sostman HD, Henschke CI. Deep venous thrombosis: detection by using
indirect CT venography. The Pulmonary Angiography-Indirect CT Venography
Cooperative Group. Radiology. 2000 Sep;216(3):744-51
Tom Meagher MRCP FRCR
Richard Graham MA
Dept of Radiology
Buckinghamshire Hospitals Trust
Competing interests:
None declared
Competing interests: No competing interests