Saturday, August 17, 2013

Should American Journal of Neuroradiology Commentary be Evidence-Based?

Should American Journal of Neuroradiology Commentary be Evidence-Based?
AJNR Blog

Published online before print July 11, 2013, doi: 10.3174/ajnr.A3671
AJNR 2013

A.C. Mamourian
Department of Radiology, Neuroradiology

B.A. Pukenas
Department of Radiology, Neurointervention
Hospital of the University of Pennsylvania
Philadelphia, Pennsylvania

S.R. Satti
Department of Neurointerventional Surgery
Christiana Care Heath System
Wilmington, Delaware

After the editorial alarmingly entitled "Death by Nondiagno­sis: Why Emergent CT Angiography Should Not Be Done for Patients with Subarachnoid Hemorrhage"1 in the American Jour­nal of Neuroradiology (AJNR) in 2007, we were looking forward to an update in Dr Jayaraman's recent commentary, "Cerebral An­giography: Not Yet Ready to Join the Dinosaurs,"2 after 6 years of progress with CTA technology. On the basis of the title of the piece, we expected to read a commonsense plea for neuroradiolo­gists to maintain their competence with catheters now that CTA has effectively become the first imaging test at many hospitals for patients presenting with nontraumatic subarachnoid hemor­rhage. Therefore, we were surprised to read about his suggestion to bypass CTA altogether and go directly to DSA whenever possi­ble, a point of view reminiscent of that 2007 editorial.

His commentary was in response to a scientific article in which Delgado Almandoz et al3 reported that 10%–20% of patients with acute subarachnoid hemorrhage but negative CTA or MRA had positive findings on DSA. This is of interest but not surprising and less so when one considers that only approximately 11 cases a year (18%) had negative CTA findings over the course of 5 years at their institution. In only approximately 3% (15% of 18%) of all the patients presenting to their hospital with subarachnoid hem­orrhage, angiography was required to find the source of the hem­orrhage. If we choose to look at the glass half full, in 97% of their patients CTA alone provided the correct diagnosis. That is better than most other diagnostic tests used routinely. Nevertheless, DSA was necessary to find that 3% in 18% of their patients, so let us say that CTA alone provided the correct diagnosis in approxi­mately 80%.

He then cited another article that reported that even when the CTA findings are positive, the DSA examination changed the treatment plan in 20%–30% of patients.4 While that certainly would support his argument, some of the "changes" listed in that article would be insignificant in the setting of a patient with an acute subarachnoid hemorrhage. For example, a 4-mm anterior communicating artery aneurysm noted on CTA was 1 example of "change" when it was found to be to a 5-mm aneurysm on DSA. Acute subarachnoid hemorrhage was not required for inclusion in the study and, in both articles, MRA was lumped together with CTA in the pre-DSA group. That explains the title of the Delgado Almandoz3 article, "Diagnostic Yield of Catheter Angiography in Patients with Subarachnoid Hemorrhage and Negative Noninva­sive Examinations" (italics ours). Therefore, while neither article directly addresses the question of CTA versus DSA in patients with subarachnoid hemorrhage, let us accept that there is some­thing to what they say and call CTA diagnostic in only 70% of cases.

With these facts in hand, Dr Jayaraman goes on to remind the readers of their obligation as physicians to eliminate unnecessary costs to the health system and concludes: "As part of this cost containment, if we can eliminate a 'good' test (CTA) to go directly to the 'best' test (DSA), I believe that we should take this oppor­tunity…. Doing so may decrease the cost and will also decrease patient radiation dose."2

"May" indeed. One might then ask on what basis? The com­mentary does not offer any numbers to support the advice to skip CTA. At our institution, the charge for DSA is approximately 5 times that of CTA. The difference may be even larger at other institutions, and that differential makes perfect sense considering that DSA is an invasive test (one that requires an hour or more to perform, catheters and the like, and with physicians in atten­dance) and should cost considerably more than CTA to perform. With regard to radiation dose, we rely on the report by Manninen et al,5 in which they used real measurements to show that CTA of the intracranial vessels has only one-fifth the effective dose of a DSA examination.

For keeping score, let us assign to CTA a relative cost value of 1 and the same for its dose. Using their relative values for a single brain DSA, we will assign a value of 5 for cost and 5 as well for dose. If we were to then choose to examine the next 100 patients who arrive at the emergency department with a subarachnoid hemorrhage with a DSA study as their only examination instead of a CTA, doing the "best" test first, as suggested in the commen­tary, the total cost in terms of our relative values would be 500 (5 x 100) for cost and 500 (5 x 100) for dose—that is, of course, assuming that there were no complications from the DSA, be­cause they would certainly increase both the cost and dose of this approach. Now let us reset the counter and offer each patient a CTA at the time of presentation. The total cost for the CTA part of their work-up would then be 100, and their total dose, 100. Now then if we assume that 30% of the 100 had normal or less-than­definitive CTA findings followed by DSA, if we used our relative-value scale, that would require an additional cost of 150 (30 x 5) and dose of 150 (30 x 5). The total then for the approach of using CTA followed by DSA in our group of 100 in total would add up to 250 for cost and 250 for dose compared with 500 and 500, respec­tively, for the DSA-only model. In short, using the DSA-first ap­proach suggested by Dr Jayaraman would incur twice the cost and dose. While there may be flaws with this simple calculation, we believe, in broad strokes, that it is sound, and at least we offer an analysis to support the CTA-first approach.

What should be acknowledged at the outset is that in clinical practice, DSA is usually performed as part of the patient's endo­vascular procedure and not as a stand-alone diagnostic test. That is why this question of cost and dose is really quite complex. At most centers, CTA is used as a decision point on the way to sur­gical or, more frequently, endovascular treatment of an aneu­rysm. The benefit of endovascular treatment in this circumstance was recently reaffirmed by the Barrow Ruptured Aneurysm Trial from the Barrow Institute.6 Using CTA as the first examination is helpful in many ways: For example, it can determine whether the patient requires emergent surgery, it allows the family to under­stand the magnitude of the risks before any treatment, and it allows the interventionalist to limit the diagnostic portion of the endovascular procedure and decide how to best address the spe­cifics of the aneurysm configuration before the procedure. Be­cause diagnostic angiography is commonly performed without anesthesia but interventional procedures are not, one would have to consider the implications, in terms of cost, of performing a diagnostic DSA examination without anesthesia and then bring­ing in anesthesia, compared with the cost of doing all DSA exam­inations with anesthesia in anticipation of some going on to in­tervention. It is for these reasons that the impact of bypassing CTA goes well beyond any simple measure of sensitivity, because even a negative CTA finding in the middle of the night has a significant impact on patient care regardless of the results of the DSA that follows the next day.

We can all agree that CTA alone cannot address all the diag­nostic questions for these patients with subarachnoid hemor­rhage. Moreover, for those patients who need DSA for diagnosis, we wholeheartedly agree with Dr Jayaraman that neuroradiolo­gists need to be well-trained and prepared to offer optimal DSA imaging with minimal risk whenever necessary. However, until real evidence is provided to the contrary, we believe that CTA remains the logical first examination for patients presenting with subarachnoid hemorrhage.

References

  1. Kallmes DF, Layton K, Marx WF, et al. Death by nondiagnosis: why emergent CT angiography should not be done for patients with subarachnoid hemorrhage. AJNR Am J Neuroradiol 2007;28:1837–38
  2. Jayaraman MV. Cerebral angiography: not yet ready to join the di¬nosaurs. AJNR Am J Neuroradiol 2013;34:840
  3. Delgado Almandoz JE, Crandall BM, Fease JL, et al. Diagnostic yield ofcatheter angiographyinpatientswith subarachnoidhemorrhage and negative initial noninvasive neurovascular examinations. AJNR Am J Neuroradiol 2013;34:833–39
  4. Tomycz L, Bansal NK, Hawley CR, et al. Real-world comparison of non-invasive imaging to conventional catheter angiography in the diagnosis of cerebral aneurysms. Surg Neurol Int 2011;2:134–40
  5. Manninen AL, Isokangas JM, Karttunen A, et al. A comparison of radiation exposure between diagnostic CTA and DSA examina¬tions of cerebral and cervicocerebral vessels. AJNR Am J Neuroradiol 2012;33:2038–42
  6. McDougall CG, Spetzler RF, Zabramski JM, et al. The Barrow Rup¬tured Aneurysm Trial. J Neurosurg 2012;116:135–44

Reply

Published online before print July 11, 2013, doi: 10.3174/ajnr.A3703
AJNR 2013

M.V. Jayaraman
Departments of Diagnostic Imaging and Neurosurgery
Warren Alpert School of Medicine at Brown University
Providence, Rhode Island

I would like to thank Drs Mamourian, Pukenas, and Satti for their letter, "Should American Journal of Neuroradiology Com­mentary Be Evidence-Based?" I agree that commentary should indeed be evidence-based. However, with many studies, there can be more than one way to interpret the data.

I stated in my original letter that "we as radiologists should do our part to optimize patient care by eliminating redundant test­ing…."1 Recently, McDonald et al2 published an analysis of the relative use of CTA and DSA in patients with ruptured cerebral aneurysms. They showed that in a retrospective analysis of 4972 patients (3950 of whom were treated with endovascular coiling) spanning 2006–2011, the use of CTA increased from 20% in 2006 to 44% in 2011. Meanwhile, during the same time, the use of angiography remained unchanged at 94%–96%. This evidence seems to support the assertion that in patients with ruptured an­eurysms, increasing use of CTA did not decrease the use of DSA. Certainly, this retrospective study has limitations, the most signif­icant of which is that patients with nonaneurysmal subarachnoid hemorrhage were not included.

Mamourian et al also suggest that pretreatment CTA "is very helpful to determine whether the patient requires emergent sur­gery, it allows the family to understand the magnitude of the risks before any treatment, and it allows the interventionalist to limit the diagnostic portion of the endovascular procedure and plan before the procedure how to best address the specifics of the an­eurysm configuration." However, there is no evidence that they can reference to support that claim. Where is the evidence show­ing that pretreatment CTA improves outcomes or patient safety among those who subsequently undergo endovascular therapy? Where is the evidence that a pretreatment CTA reduces proce­dural time or radiation exposure during diagnostic angiography?

Because they also state that CTA "remains the logical first ex­amination for patients presenting with subarachnoid hemor­rhage," I would suggest that they provide the evidence that sup­ports this claim. Perhaps they should randomize all patients with SAH to either CTA first or DSA first. Then, when they can show that the CTA-first group had better outcomes and lower costs, they can support their logic. It may also have been logical to be­lieve that endovascular therapy is better than the best medical therapy for intracranial atherosclerotic disease3 or that logically, endovascular therapy improves outcomes over IV thrombolysis alone in patients with acute ischemic stroke.4

I certainly believe that CTA has an important role in the emer­gent setting. Patients who are too unstable to undergo angiogra­phy or need emergent resection of an intracranial hematoma are excellent candidates for a CTA. In addition, those with low suspi­cion for aneurysmal hemorrhage can also often be managed with CTA alone. Indeed, the original article that started this discussion showed that in patients with isolated perimesencephalic hemor­rhage, negative findings on noninvasive imaging would have been adequate.5 However, at the present time, there is inadequate evi­dence to imply that CTA as a first imaging technique on all pa­tients with subarachnoid hemorrhage should be the standard of care.

References

  1. Jayaraman MV. Cerebral angiography: not yet ready to join the di­nosaurs.AJNR Am J Neuroradiol 2013;34:840
  2. McDonald JS, Kallmes DF, Lanzino G, et al. Use of CT angiography and digital subtraction angiography in patients with ruptured ce­rebral aneurysm: evaluation of a large multihospital data base. AJNR Am J Neuroradiol 2013 Apr 11. [Epub ahead of print]
  3. Chimowitz MI, Lynn MJ, Derdeyn CP, et al., for the SAMMPRIS Trial Investigators. Stenting versus aggressive medical therapy for intra­cranial arterial stenosis. N Engl J Med 2011;365:993–1003
  4. Broderick JP, Palesch YY, Demchuk AM, et al. Endovascular therapy after intravenous t-PA versus t-PA alone for stroke. N Engl J Med 2013;368:893–903
  5. Delgado Almandoz JE, Crandall BM, Fease JL, et al. Diagnostic yield of catheter angiography in patients with subarachnoid hemorrhage and negative initial noninvasive neurovascular examinations. AJNR Am J Neuroradiol 2013;34:833–39

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