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ALiEM-Annals of EM Journal Club: Clinical Decision Rule for Subarachnoid Hemorrhage


We are very excited this month to bring you our second Global Journal Club, co-hosted by the team here at ALiEM and the editorial board at the Annals of Emergency Medicine. This month, we are changing things up! We will be providing you, our readers, with a clinical vignette and related journal club questions today at the beginning of the week.The discussion will be held asynchronously starting today through Thursday (for 4 days). Respond by blog comment below or tweet (#ALiEMJC).

On Wednesday, January 22, 2014 at 11 am PST (2 pm EST), we will be hosting a 30-minute live Google Hangout with Drs. Jeff Perry and Ian Stiell. The video will be embedded on this page. During this period, you will be able to tweet by using the #ALiEMJC hashtag and post comment in the blog comment section below.

Clinical Vignette

It is 8 pm on a Wednesday night. Your shift ends in two hours, and you are just beginning the latter half of your shift in the quick-care area.

Your next patient is a 24-year-old female with a headache.

She discloses that she has had the worst headache of her life occur about 3 hours ago. Her husband explains that she is not a ‘complainer’ and that he is quite worried because the headache occurred quite quickly, peaking within a hour of its onset. She doesn’t usually get headaches. In the ED, she has vomited once. She is afebrile, non-toxic in appearance, and although she complains of mild neck pain, you do not note any frank nuchal rigidity. She has mild photophobia and phonophobia, but there are no focal neurologic deficits when you examine her.

She is very relieved to see that you are empathetic to her concerns, and you quickly arrange a CT scan to rule out a subarachnoid hemorrhage (SAH). In the meantime, you also provide her with analgesics and an antiemetic.

The 64-slice CT scan is read by the second-year radiology resident on call as negative for SAH. Just as you are about to consent the patient for a lumbar puncture (LP), a senior resident in the department asks you: “Wasn’t there a study by Perry et al. that suggested you don’t need to do an LP anymore? Can’t you just rule out SAH with the clinical decision rule that they proposed?”

Featured Journal Club paper

Perry JJ, Stiell IG, Sivilotti ML, Bullard MJ, Hohl CM, Sutherland J, Émond M, Worster A, Lee JS, Mackey D, Pauls M, Lesiuk H, Symington C, Wells GA. Clinical decision rules to rule out subarachnoid hemorrhage for acute headache. JAMA. 2013 Sep 25;310(12):1248-55. PubMed PMID: 24065011

Live Google Hangout with Authors Dr. Perry and Stiell

Edited Podcast Version of Google Hangout


IMPORTANCE: Three clinical decision rules were previously derived to identify patients with headache requiring investigations to rule out subarachnoid hemorrhage.

OBJECTIVE: To assess the accuracy, reliability, acceptability, and potential refinement (ie, to improve sensitivity or specificity) of these rules in a new cohort of patients with headache.

DESIGN, SETTING, AND PATIENTS:Multicenter cohort study conducted at 10 university-affiliated Canadian tertiary care emergency departments from April 2006 to July 2010. Enrolled patients were 2131 adults with a headache peaking within 1 hour and no neurologic deficits. Physicians completed data forms after assessing eligible patients prior to investigations.

Subarachnoid hemorrhage, defined as (1) subarachnoid blood on computed tomography scan; (2) xanthochromia in cerebrospinal fluid; or (3) red blood cells in the final tube of cerebrospinal fluid, with positive angiography findings.

RESULTS: Of the 2131 enrolled patients, 132 (6.2%) had subarachnoid hemorrhage. The decision rule including any of age 40 years or older, neck pain or stiffness, witnessed loss of consciousness, or onset during exertion had 98.5% (95% CI, 94.6%-99.6%) sensitivity and 27.5% (95% CI, 25.6%-29.5%) specificity for subarachnoid hemorrhage. Adding “thunderclap headache” (ie, instantly peaking pain) and “limited neck flexion on examination” resulted in the Ottawa SAH Rule, with 100% (95% CI, 97.2%-100.0%) sensitivity and 15.3% (95% CI, 13.8%-16.9%) specificity.

CONCLUSIONS AND RELEVANCE: Among patients presenting to the emergency department with acute nontraumatic headache that reached maximal intensity within 1 hour and who had normal neurologic examination findings, the Ottawa SAH Rule was highly sensitive for identifying subarachnoid hemorrhage. These findings apply only to patients with these specific clinical characteristics and require additional evaluation in implementation studies before the rule is applied in routine clinical care.

Notable tables from the paper (Box 1 and 2)

Rule 1 Investigate if ≥ 1 high-risk findings present:
1. Age ≥ 40 years
2. Neck pain or stiffness
3. Witnessed loss of consciousness
4. Onset during exertion
Rule 2 Investigate if ≥1 high-risk findings present:
1. Age ≥ 45 years
2. Arrival by ambulance
3. Vomiting (≥1 episode)
4. Diastolic blood pressure ≥ 100 mmHg
Rule 3 Investigated if ≥1 high-risk findings present:
1. Age 45-55 years
2. Neck pain or stiffness
3. Arrival by ambulance
4. Systolic blood pressure ≥ 160 mmHg
Ottawa SAH Rule

For alert patients >15 years with new, severe nontraumatic headache reaching maximum intensity within 1 hour:

Investigate if ≥1 high-risk variables present:
1. Age ≥ 40 years
2. Neck pain or stiffness
3. Witnessed loss of consciousness
4. Onset during exertion
5. Thunderclap headache (instantly peaking pain)
6. Limited neck flexion on examination

Not for patient with new neurologic deficits, previous aneurysms, SAH, brain tumors, or history of recurrent headaches (≥3 episodes over the course of ≥6 months)

Featured Questions for our Audience

Two questions were selected from those published in this month’s Journal Club questions published in Annals of EM [free PDF] and two questions posed by the ALiEM team to address more issues of how HOW and WHETHER these results change practice (i.e. knowledge translation). Of course if you have additional questions, feel free to pose them!

Annals of EM questions

In this article, 26% of patients arrived by ambulance, and “arrival by ambulance” was one of the 4 variables in rule 2.  The inclusion of this variable suggests that patients arriving by ambulance are at greater risk for subarachnoid hemorrhage.

In some settings, patients arriving by ambulance are automatically triaged to higher-acuity beds.

  • Q1: How might the patient’ s location in the ED when treated by the clinician affect the evaluation that he receives?
  • Q2: Why might this be especially important for EDs that employ midlevel providers or resident moonlighters to staff the low-acuity areas?

ALiEM Questions

  • Q3: In your clinical practice, what information do you provide when counseling patients about the role of lumbar punctures for ruling out SAH?
  • Q4: In a teaching centre, how do you integrate learning with patient care? Is the read of a second year radiology resident sufficient for ruling out SAH in this patient? Does this paper answer this question?

Please participate the journal club by answering either on the ALiEM blog comments below or by tweeting us using the hashtag #ALiEMJC. When responding, please denote the question to which you are responding by writing Q1, Q2, Q3, or Q4. For example:

Q4: Our reads are usually double-checked by attending radiologists in the morning.

We reserve the right to use any and all tweets to #ALiEMJC and comments below in a commentary piece for an Annals of Emergency Medicine publication as a curated conclusion piece for this global journal club. Your comments will be attributed, and we thank-you in advance for your contributions.

UPDATE 7/17/14

The curated responses from discussions on the various platforms have been published in Annals of EM: PMID 24951414 

Teresa Chan, MD
ALiEM Associate Editor
Emergency Physician, Hamilton
Assistant Professor, McMaster University
Ontario, Canada + Teresa Chan
  • TChanMD

    Thanks for starting this out Michelle! I think this paper and the other ones that have come out of the Ottawa research group have been very important questions to note.

    What do people think about this 2013 paper though? I think it integrates well with their previous work.

  • Salim R. Rezaie

    Theresa and Michelle,

    Great topic and great article. This could truly be a game changer if the Ottowa SAH Rule and the Perry et al article ( get used in conjunction with each other. This could decrease the number of LPs and Head CTs needed to workup this diagnosis. That being said, I have a few thoughts and will try and answer the questions one at a time.

    In general, when a clinical decision rule is created, it does very well in the original study population, and tends to not do as well later on (i.e. San Francisco Syncope Rule). Secondly, this study was done in Canada, which has a totally different medico legal system than the United States, with the U.S. having a more litigious society. Finally, The major limitation of both sensitivity and specificity is that they are of no practical use when it comes to helping the clinician estimate the probability of disease in individual patients. With that being said….

    Q1: Often times in lower acuity areas, it is easy to anchor a physician, resident, physician assistant to a lower acuity diagnosis. This can be very dangerous, and lead to more missed diagnosis. Everyone of us has been guilty of this anchoring bias, and important to remember (i.e. Massive PE or STEMI in the fast track area).

    Q2: A clinical decision rule could be a way to help standardize a diagnosis algorithm to someone with less clinical experience to make sure that they evaluate the patient correctly for a particular diagnosis. This could help them justify their clinical decision making (i.e. A low HEART score in evaluation of ACS in the ED). But again sensitivity and specificity are based on a diagnosis, and patients usually do not present with a diagnosis, but a constellation of symptoms.

    Q3: The reason the Perry et al original paper and this paper are so practice changing is that if patients present in <6hours, now you can say…without an LP I have a sensitivity of 100% (at least to date). Where this gets tricky is when the duration has been longer than 6 hours. Afer 6 hours the sensitivity of head CT alone falls quickly to 90% and even lower at 1 week. These are the numbers I have often quoted to my patients.

    Limitations of Head CT: Sensitivity decreases after 6 hrs of symptom onset, small volume bleeds may not be detected, less experienced radiologists may have decreased sensitivity compared with experienced neuroradiologists, and patients with hct < 30% may have a falsely negative CT scan of the head

    Limitations of LP: Xanthochromia may be absent at 2weeks, there is no guideline for the number of RBCs to dx SAH.

    Finally this is a great article, although on aneurysmal bleeding does a very nice job of going through all the pros and cons of the above modalities:

    Q4: I don’t know about others, but at my shop after 5pm all we have are resident radiologists, and if you are the 7am person…the phone goes off the hook for over-reads and missed diagnoses. This paper certainly does not answer this question and is a very important point to bring up….does a negative head CT even at <6hours read by a resident radiologist and not a staff neuroradiologist mean that SAH has been ruled out? No offense to my radiology residents, but I think the answer to this question is no. If you are lucky enough to work at an institution that has 24-7 faculty radiology, then ignore my previous statement.

    Enough rambling by me…would love to hear others thoughts.


  • Rory Spiegel

    Question 4 is probably the most important aspect of the Perry et al paper examining whether a CT performed within 6 hours of symptom onset is adequate to safely exclude SAH (1)? For the most part I tend to agree with Salim, in that the Perry study demonstrated CT performed within this time frame was fairly effective. I do however have a few concerns about interpreting this single study as truth. The standard that Perry
    et al used to calculate the sensitivity of head CT was based upon a Neuroradiologist’s official report. In most facilities (as was the case at the centers participating in this study) what guides Emergency Physicians’ clinical decision-making is the initial wet read usually done by radiology house staff or even the ED physicians themselves. The sensitivity we are concerned with is of that wet read. What we cannot ascertain from the published data is how many CTs done within 6 hours were initially read as negative, and
    only later after a positive LP was the final report recorded as positive(the
    Neuroradiologists in this study were not blinded to the patients lab findings)?
    If this had occurred with any frequency it would obviously harm the external
    validity of this trial. We could get a sense of how frequently this occurred by
    examining how many of the patients who were diagnosed with SAH had both a
    positive CT and LP. At least in theory, if the CT was positive then there would
    be no reason to perform an LP.

    In the initial derivation cohort, 42.7% of the patients received both a CT and LP (1,2). How many of those patients had both a positive CT and LP? Unfortunately this data is not available. When the validation cohort is examined, 40.6% received both a CT and LP(3). Of these 16.7% were eventually diagnosed with SAH (3). How many of these patients received a CT within the first 6 hours of symptom onset? This would be the subgroup of patients in whom the wet read was most likely negative. This is the true sensitivity we should use to guide or decision-making. I would be interested in Dr. Perry and Dr.
    Stiell’s thoughts on this and how strongly this might affect our interpretation of the results.

    1. PerryJJ,StiellI IG,etal.Sensitivityof computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage: prospective cohort study. BMJ. 2011;343:d4277.

    2. Perry JJ, Stiell IG, Sivilotti ML, et al. High-risk clinical characteristics for
    subarachnoid haemorrhage in patients with acute headache: prospective cohort
    study. BMJ. 2010;341:c5204.

    3. Perry JJ, Stiell IG, Sivilotti MA, et al. Clinical Decision Rules to Rule Out Subarachnoid Hemorrhage for Acute Headache. JAMA. 2013;310(12):1248-1255.

    • Michelle

      Sent from Mailbox

    • TChanMD

      Hi Rory! Thanks for chiming in. Love your work always, and this post especially!

      Thanks for bringing in the OTHER important works of Drs. Perry & Stiell. I’m glad you picked up on this very important aspect of the relatedness of their program of research.

      Yes, I’m fascinated to hear what Drs. Perry & Stiell have to say about the combination of their prior work on CT head within 6 hours (BMJ 2010) and this present SAH CDR (JAMA 2013).

      Through #ALiEMJC we are trying to bring all this work to the bedside via this line of reasoning and connect the dots (instead of just discussing one paper at a time). Would love to hear your thoughts more on this matter, Rory!! 😀

  • While I agree that maybe this will make us better at diagnosing the SAH, the paper itself stated that they did not decrease the number of studies performed. Since some of the discussion here also involves who reads the CT, I figured I would add the other fly in the ointment. This paper didn’t discuss the type of scanner, at least as far as I could tell. Since much of the newer literature involves 64 slice or more MDCT, I will say that not every shop has those. My academic site only has a 16 slice, so what is the external validity of this to many of the rural places?

    • TChanMD

      I think this brings up a great point – and it might be why Drs. Perry & Stiell et al went on to derive the SAH CDR? What do you think? Then you can use the rule to decide who needs to be shipped for a proper 64 slice CT scan?

    • Brent Thoma

      Justin, I think that’s an important point. I noted the reference to the Vermeulen study which found that SAH’s were misdiagnosed 5.4% of the time (data from 2002-2005), but did not see data on whether those patients were CT’d or not. If they were missed because we didn’t look, then this rule might help “improve our aim” so we CT the same number of people with less misses.

      Your question regarding the application of this rule in centers with older technology is a good one and has a nice parallel with the question of who to trust reading the scan. I imagine that question won’t go away until it becomes obsolete because your scanner gets upgraded.

  • Anand Swaminathan

    Great article to discuss for Journal Club. We just did this article last week in our residency program. I’d love to say something smart but I think Salim, Rory and Justin have covered many of the important issues.
    Q3 – If the patient has low – moderate risk features and a negative CT < 6 hours, I tell them that their risk of SAH is low, around 0.5 – 1% (using a pretest prob around 7% based on the prior Perry study and Fagan nomogram). I tell them that LP will virtually rule out the diagnosis. I ask them what their comfort level is and do a little shared decision making. I also tell them that LP has false positives etc. This can be a difficult discussion when there's a language barrier (even with good translators) and that has to factor in as well.
    Q4 – Like Salim, I have junior radiology residents after midnight and no neuroradiologist from 5 pm – 8 am. so I have the same hangup. No good answer here from these papers.

    I will note that in this study, the decision rules increased the number of CTs performed so no reduction in cost or workup rates.

    As with all decision instruments, we need validation (if I remember correctly, they are working on that now). Unlike ankle or knee rules, this is a much more complex issue making it more difficult to form a decision rule. Additionally, the stakes are much higher. If I miss an ankle injury, big deal. If I miss an SAH, BIG DEAL. Forget about medicolegal, this can be a disaster for the patient.

    Lastly, remember that SAH isn't the only thing that causes severe headaches. We have to think about meningitis, vertebral artery dissection, temporal arteritis, encephalitis etc. etc.

    • Andywebster

      agree with the above comment shared decision making is very important

      • Michelle

        Sorry for missing your Q on the hangout! Posted your Q on a new comnent thread here.

  • Michelle

    Sorry to Andrew Webster who asked a Q on the Google Hangout, but we ran out of time! Maybe we can address here?

    “Do you see a role for CT angiogram in the work up of these headache patients. With the difficulties of knowing we may pick up asymptomatic cerebral aneurysms?”

    • Anand Swaminathan

      Not a huge fan of CTA. The issue, as you put it, is the asymptomatic cerebral aneurysm. The rate of this increases as the population ages. The question at hand is how can you know if the aneurysm you find on CTA is responsible for the headache. If you have a high post-test probability (in spite of CT being negative) you need to do the LP.

      • Rory Spiegel

        I agree with Anand, using CT/CTA as a diagnostic pathway to rule out SAH will inevitably lead to the frequent misclassification of incidental aneurysm in an otherwise benign headache. Studies have found the rate of asymptomatic unruptured cerebral aneurysms in the general population as high as 7%(1). This would obviously lead to a great deal of false positive CTAs and unnecessary downstream testing.

        In addition to this decrease in specificity, there is no evidence CT/CTA adds any diagnostic value to our current management of suspected SAH. Currently our knowledge of the diagnostic accuracy of CTA for SAH is based primarily off small cohorts trials comparing CTA to the gold standard of DSA in patients who have already been diagnosed with CT +SAH. Even in this population the sensitivity of CTA ranges from 81% to 99% (2-5). These studies do not inform us how CTA performs when identifying aneurysms in patients with SAH not visualized by a non-contrast CT. CT/CTA as a protocol for the diagnosis of SAH has never been formally investigated in undiagnosed patients presenting with thunderclap headache. If one assumes independence of the two tests and applies the more optimistic test characteristics for CTA, then the post-test probability following a negative CT and CTA may be clinically useful. Unfortunately, given the current data we are unable to assume independence between these two tests. If the aneurysms that are missed by CTA are the same ones that are commonly read as negative on CT, then this protocol will add very little sensitivity to CT alone. This concept is demonstrated nicely in a paper by McCormack et al, published in Academic Emergency Medicine (6). In this paper the authors calculate the posttest probability following a negative CT and CTA given 25, 50, and 75% dependence. In the case where the tests only had 25% dependence the post-test probability of a negative CT and CTA would be 0.29% (or 1 in 344 patients). On the other hand if you were to assume 75% dependence between the tests, then the post-test probability would be 0.86% (1in 116 patients),very close to the post-test probability of a negative CT alone.

        Without formal investigations evaluating the performance of a CT/CTA in the diagnosis of SAH we are unable to know its diagnostic utility. If these tests end up having a significant degree of dependence, not only will this protocol increase the rate of false positive findings, it will not be sufficiently sensitive to rule out the high risk patient.

        1. Ming-Hua et al Prevalence of Unruptured Cerebral Aneurysms in Chinese Adults Aged 35 to 75 Years A Cross-sectional Study. Annals of Internal Medicine. 2013 Oct;159(8): 514-521.
        2. MaccKinnon et al. Acute Subarachnoid Haemorrhage: Is a Negative CT
        Angiogram Enough? Clinical Radiology, Vol. 68, Issue 3, 232-238
        3. Ergun et al. Diagnostic Value of 64-slice CTA in Detection of Intracranial Aneurysm Patients with SAH and Camparison of the CTA Results with 2D-DSA and Intraoperative Findings
        4. Kokkinis et al. The Role of 3d-Computer Tomography Angiography(3D-CTA) in Investigation of Spontaneous Subarachnoid haemorrhage: Comparison with Digital Subtraction Angiography (DSA) and Surgical Finding. British Journal of Neurosurgery. Vol. 22:71-78
        5. Westerlaan et al. Multislice CT Angiography in the Selection of Patients with Rupture Intracranial Aneurysms Suitable for Clipping or Coiling.
        Neuroradiology (2007) 49:997-1007
        6. McCormack et al. Can Computed Tomography Angiography of the Brain Replace Lumbar Puncture in the Evaluation of Acute-onset Headache After a Negative Noncontrast Cranial Computed Tomography Scan? Volume 17, Issue 4, pages 444–451, April 201)

  • Brent Thoma

    Sorry to deviate entirely from your questions, but I have one of my own: what proportion of SAH’s don’t reach maximal intensity within 1 hour? I would have been interested in hearing from the authors whether there were any SAH’s missed at the hospitals during the study period that didn’t meet this inclusion criteria. Would you apply the rule to a patient that says it peaked within “a couple of hours”?

  • Seth Trueger

    I think all the comments are fantastic and will try to focus my thoughts on something novel instead of re-describing the newly invented wheel.

    First, I’ve seen a few people question the use of six-month followup as a proxy (including Ryan Radecki, and Jerry Hoffman in EMA on the prior 6-hour CT for SAH paper), particularly since many patients didn’t get a CT and most didn’t get an LP. I think that it’s a pretty good marker — if the patient is alive & well at 6-months (even if I missed their SAH) then I imagine they are pretty happy about it.

    Second, the specificity is pretty poor. It’s pretty easy to be 100% sensitive, but 15-30% is pretty poor specificity.

    Third, I think Jerry Hoffman makes a great point: it’s just an LP. They’re not that hard, they’re not that time consuming, they’re pretty benign, they give a clear answer most of the time, and when they do give a clear answer, it’s a nearly perfect test. To me, that means we need a pretty good reason to NOT do the LP.

    I think the calculated 1% post-test prob. Anand (and Newman) quote is pretty reasonable, and for the most part, and almost gets us to not doing the LP, but not quite. I absolutely agree that this is a perfect time to use shared decision making — why should we make the call the balance the patient’s risk of missing a potentially life-altering diagnosis vs low risk of harm/needle in the back? But it’s a procedure that has the same complication rate as a peripheral IV (I’ve been told), works better than most tests, and diagnoses one of the worst diseases.

    And for what it’s worth, I agree CTA is worthless. Far too many asymptomatic aneurysms compared to aneurysmal SAH… which of course is *literally* how you get a terrible LR+

    • TChanMD

      I would say, without disclosing too much, as a patient who has had a multi-attempt LP… It can be a very uncomfortable and long drawn ordeal. 🙁

      • Seth Trueger

        Absolutely, I do not mean to diminish the drawn-out pain of a tough or poorly-anesthetized LP. But the horrible ones (for the patient) are a small fraction, and I imagine dying of a SAH is pretty bad as well (I don’t mean to be so blunt but can’t find a better way to word this)

    • Matthew


      I agree that most of the time an LP is a fairly safe procedure that can be done easily under most circumstances. My issue with LP is that in reality it can be a pretty confusing test. The rate of traumatic tap has been reported to be 10-15%. While most of us will see a few red cells in tube 1, assume it is from trauma, and then look for clearing throughout the subsequent tubes, there isn’t a whole lot of data to support this practice.(

      Often I’ll see what looks like a traumatic tap with some evidence of clearing, I’ll discuss with Neurosurgery, who will ask for a CTA and then discharge the patient if negative. I have a very hard time getting any Neurosurgeon to discuss the possibility of SAH in a patient who has a normal CTA, no matter what the LP shows.

      I’m not anti-LP but I think there is a fair bit of diagnostic uncertainty in the event that you get anything but a totally bloodless tap.

      I also agree that going straight to CTA is a bad move. In addition to the risk of finding tons or asymptomatic aneurysms, one study found that ~50% of CT negative/LP + SAH were “non-aneurysmal” which means they would have likely not been detected if the provider had just done a CTA. (

      • Seth Trueger

        I agree- clearance is useless. The bottom line is the tube with the lower RBCs is the # of RBCs we use. The reason why the neurosurgeons care about the CTA in a possibly traumatic tap is that neurosurgeons are surgeons, and they don’t operate on Hunt & Hess perimesencephalic SAH. The question they’re asking with the CTA isn’t “does this patient have a bleed” but rather “can I operate?”

        • Matthew

          Agreed, the problem I have with the Neurosurgeons approach is that while the large majority of the perimesencephalic bleeds do fine, ~10% have bad outcomes, so the idea of “no aneurysm, no bleed” really is absurd. The unfortunate reality is that in most shops, neurosurgeons are the only guys to call if you’re concerned about SAH. I know a good number of community docs who go straight for the CTA because even if they get gross blood in a tube, all the NS is going to care about is the CTA. There is also this notion that “a patient would want to know if they have an asymptomatic aneurysm that needs watching” which tends to downplay the risk of finding these incidental aneurysms on CTA.

          • Seth Trueger

            But remember: an aneurysm found on a CTA is not “an asymptomatic aneurysm that needs watching”

          • Matthew

            Often time this is what it becomes. My partner had a patient with chronic migraines who came in with a “different” headache. Got a CTA which showed a small aneurysm. Neurosurgery didn’t intervene, and now the pt continues to have chronic headaches but has the word aneurysm all over their chart.

  • Minh Le Cong

    thanks folks for the discussion.
    check out this coroners report

    I would be careful about dismissing the role of CTA in workup of SAH!

    • Seth Trueger

      She got the CTA — and it found the aneurysm!

  • Tyler W. Barrett, MD

    Hey everyone. Thanks for the great discussion about this article. As one of the Annals EM Journal Club editors, I wanted to introduce an additional discussion topic.

    In Question 3A of this month’s Annals JC, we asked the following: “The specificity of the Ottawa subarachnoid hemorrhage rule is such that nearly 85% of patients with potentially concerning headache would require computed tomography (CT) and lumbar puncture. The present accepted standard for a subarachnoid hemorrhage evaluation includes a nonenhanced CT study and, if the CT result is negative, a lumbar puncture. Using the data provided in the article, calculate the percentage of the of the entire cohort who underwent this complete evaluation… What is your best estimate of how many patients received a complete evaluation by the physicians, and how does this compare with the 85% who would receive an evaluation under the Ottawa clinical decision rule?

    The JAMA article’s Figure implies that 25% (539 of 2131) patients had an “actual” workup (CT positive or CT negative followed by lumbar puncture performed). Table 1 suggests that 38% (807 of 2131) patients had both CT and lumbar puncture and there will be additional patients who had a positive CT and therefore did not require CT who
    will take that % higher. It is unclear to us why the number in the Figure is so much lower than that in the Table. The maximum complete workup rate in Table 1 would be 807+110=917 or 43% (917/2131) assuming that, from Table 2, 110 (132-22) patients with SAH were diagnosed with CT alone.

    Regardless of which numbers are used, all values are dramatically lower than the 85% projected to require a complete work-up if the Ottawa rule was universally employed on this population.


  • Paul Jones

    Nice to see so many familiar faces joining in the discussion on such a relevant topic to our practice in EM. One further wrinkle to consider is how applying these new rules would affect bed flow in the ED. Specifically there has been discussion about the use of the new generation CT scanners and getting a read by a staff neuro-radiologist. While I am a resident and practice in some locations with access to these sub specialist radiologist, more often I work in a community settings where there is no access to these specialists. Thus I would agree with Rory what I am interested in is the sensitivity and specificity of the “wet read” by the Emergency Medicine physician. Also I would be curious to see these trials expanded to community sites without neuro-radiologists. In the era of tele-radiology I do wonder if these types of decision rules may well create a demand for neuro-radiologists to review CT scans performed in the community (periphery) to ensure that discrepancies are caught and acted upon. Currently our EM providers do the first read of CXRs and MSK x-rays which are then followed up on by our local radiologists, does anyone else see a future where these CTs to r/o SAH will be triple read by the EM provider, local radiologist and neuro-radiologist? If this were to be the new standard, would it make sense to admit the patient until the definitive interpretation by the neuro-radiologist? Great discussion and comments. Look forward to future topics.

  • Hans Rosenberg

    For those interested Dr. Perry’s abstract to SAEM 2014 has just been accepted on the “Prospective Validation of the Ottawa Subarachnoid Hemorrhage Rule in Headache Patients”. As with the original validation study the numbers look very similar. The Sensitivity was 100% and the specificity was 14.3%. Here is the link to the full abstract: (I apologize for linking to another site but I don’t have a direct link to the document). Just thought this might be helpful for people thinking about incorporating the Ottawa SAH to their clinical practice.