Cognitive Dysfunction


Another extremely busy day, but you feel a small sense of achievement as you prepare to discharge an 87-year old man with mild lower leg cellulitis. Your euphoria quickly evaporates as the nurse tells you that several family members are concerned that the patient has recently been demonstrating increasing signs of cognitive dysfunction.

Use the Short Blessed Test to rule it out in under two minutes: Download Here



Another extremely busy day, but you feel a small sense of achievement as you prepare to discharge an 87-year old man with mild lower leg cellulitis. Your euphoria quickly evaporates as the nurse tells you that several family members are concerned that the patient has recently been demonstrating increasing signs of cognitive dysfunction. After talking briefly with the family, you can’t help but wonder (to yourself) why they are bringing this to your attention now rather than bringing it to the attention of the patient’s primary care physician (PCP).


  • Acknowledge the family’s concern and advise follow-up with the PCP
  • Initiate a full delirium work-up with the intention of making this Dr. Somebody Else’s problem.
  • Quickly assess the patient for cognitive dysfunction and modify the management plans as needed.

The Critical Question:
Is there a brief bedside test that can reliably rule in or rule out cognitive impairment in the elderly?

The Evidence
Four Sensitive Screening Tools to Detect Cognitive Dysfunction in Geriatric Emergency Department Patients: Brief Alzheimer’s Screen, Short Blessed Test, Ottawa3DY, and the Caregiver Administered AD8, Acad Emerg Med 2011; 18(4): [pages TBD].

The Bottom Line
There are three brief performance-based screening instruments to identify geriatric patients with cognitive dysfunction more rapidly than the MMSE. These are the Ottawa 3DY (O3DY), the Brief Alzheimer’s Screen (BAS), and the Short Blessed Test (SBT). Of the three, the SBT provides the best diagnostic test characteristics and overlap with MMSE results.

The term cognitive dysfunction, although very nonspecific, typically includes mild cognitive impairment (MCI), delirium, and dementia. Delirium, a transient disorder of mental capabilities, is a symptom of an acute medical illness and, therefore, considered a true medical emergency. MCI refers to decline in memory, language, or other cognitive functions and is often considered early Alzheimer’s Disease that does not otherwise impair daily living. Dementia is a more serious form of cognitive decline resulting in problems with memory, judgment, orientation, and executive functioning. While neither MCI nor dementia is an immediate threat to morbidity or mortality, dementia is a proven independent predictor of functional decline, and institutionalization. Of direct interest to us is that it also has been proven to be an independent predictor of return visit post-ED discharge. In fact, this issue has been deemed important enough that the assessment of cognitive dysfunction has recently been incorporated as a minimal core competency for emergency medicine residents and a quality indicator for all ED providers.

The current evidence shows that we don’t do well at identifying patients with cognitive dysfunction. In fact, emergency providers miss up to 70% of patients with a Mini-Mental Status Exam (MMSE) ≤ 23. The MMSE can be time consuming to apply and has not been recommended to use for the diagnosis of MCI, which requires specific tests. A number of simple screening instruments have been tested in the ED, but none have met the necessary performance characteristics needed to be of clinical value. The time pressures we face might play a role in our poor performance at identifying cognitive impairment. Ideally, we would be able to perform a bedside clinical test that is simple and has a high inter-rater reliability meaning that we all arrive at the same score when we each apply it on the same patient. And finally, and perhaps most importantly, the test must have the ability to accurately discriminate those with cognitive dysfunction from those without.

A recent study had trained research assistants test patients using the O3DY, BAS, and SBT. Each patient’s results were compared to their responses to the MMSE for which a score of less than or equal to 23 was the criterion standard for cognitive dysfunction. All enrolled subjects were non-critically ill, English-speaking adults over age 65-years and had not received any sedating medications prior to or during the testing. The investigators calculated the sensitivity, specificity, likelihood ratios, and receiver operating curve area under the curve (AUC). They also created Venn diagrams to quantitatively compare the degree of overlap amongst positive test results between the instruments.

A total of 163 patients were enrolled and the prevalence of cognitive dysfunction was 37% which included 5.5% with delirium and 3% with self-reported dementia. The SBT, BAS, and O3DY each had sensitivity of 95% with specificities of 65%, 52% and 51% respectively. The SBT also demonstrated the best likelihood ratios of 2.1 and 0.08 and an AUC similar to the BAS of 0.93.

This is a single center observational cohort study on a convenience sample of patients that provides an important first step in practice-changing information. Subsequent studies will need to validate the results, but the challenge will be finding a reference standard by which to compare the SBT and other ED-friendly instruments. This study justifiably used the MMSE, but this test has shown increased false-positive rates in poorly educated and lower socio-economic populations and increased false-negative rates in those with higher levels of education. These flaws mean that the MMSE is less than a ‘gold’ standard.

Finally, once validated as an adequate brief cognitive function screening tests, their application will need to be demonstrated as improving patient outcomes and this is best done through a randomized controlled trial.

Of the three brief performance-based screening instruments: SBT, BAS, and O3DY to identify geriatric patients with cognitive dysfunction more rapidly than the MMSE, the SBT provides the best diagnostic test performance.

The Outcome
You take a few minutes to apply the SBT to your elderly patient. His score is 3/28 indicating normal cognition. Given the high sensitivity of the test to rule out cognitive dysfunction, you’re confident in this result and reassure the family. You also advise them that more specific testing for mild cognitive impairment.



  1. Thank you for this interesting comparison. How significant is the higher level of specificity of the SBT compared to BAS and O3DY for your decision of a testing tool? Would future research compare SBT to AD8 alone, or compare all 4 in the evidence? If you didn’t use the MMSE to set a baseline, what would you use? How relevant is the time to complete the test or other factors? How did you fit the Venn diagram?

  2. Thanks for the comments. Here is the link to the PUBMED abstract which is now available (

    The significance of the higher specificity for the SBT relative to the BAS and O3DY is manifest in the negative likelihood ratios, although the differences are small (0.10 for BAS and O3DY versus 0.08 for the SBT). These values mean that a negative BAS or O3DY will reduce a 37% pre-test probability for cognitive dysfunction to 5.5% whereas a negative SBT reduces the risk to 4.5%. Probably clinically insignificant difference in diagnostic accuracy, but statistically significant based on the non-overlapping 95% CI for specificity.

    We have previously explored alternative ED-friendly cognitive screening tests ( and,, but my research team feels that the BAS, SBT, or O3DY optimize simplicity with adequate diagnostic accuracy. These publications details some of the other instruments that one might consider using as the criterion standard rather than the MMSE. We don’t plan to validate any additional instruments, but will be assessing the diagnostic accuracy for these three instruments for Mild Cognitive Impairment which the MMSE does not detect.

    The caregiver-reported AD8 is a more accurate instrument for highly educated individuals and may be a metric to assess the functional decline which new Alzheimer’s criteria mandate.

    The Venn diagrams were generated by entering the dichotomous answer (normal/abnormal) for each test on the following website:

    The time to complete the test is obviously very important for fast-paced emergency care. The O3DY is by far the simplest and fastest of the tests, but the SBT & BAS can both be administered and scored in < 2 minutes, too.

  3. How could caregivers respond? Could identification of cognitive dysfunction be used to prevent recidivism?

  4. How could caregivers respond?

    I envision several potential responses. First, about 10% of dementia cases are reversible (hypothyroid, depression, B12 deficiency, etc.). If cognitive dysfunction is confirmed via more time-intensive/definitive DSM criteria testing, these reversible dementias could be sought and treated (which they probably would not be if not recognized). Second, dementia has a spectrum of severity from mild cognitive impairment to end-stage dementia. The course of deterioration is unpredictable but relentless. Identification of sub-clinical disease states (i.e. mild cognitive impairement) will permit patients and families to begin planning for the end-stage scenario when end-of-life decisions (and financial planning, wills, etc.) can not be communicated to loved ones. Finally, numerous dementia treatment trials are underway across the nation so informed patients & families can seek these therapies (but only if informed of the diagnosis).

    Another unasked question is how emergency physicians & nurses can use this information. If cognitive dysfunction is recognized, the healthcare provider can ensure that an accurate history is obtained and discharge instructions are relayed to family caregivers so that important details are not forgotten or lost to the haze of dementia. This may have important malpractice and quality of care ramifications.

    Could identification of cognitive dysfunction reduce preventable recidivism? Multiple instruments (ISAR, TRST) incorporate dementia as an independent predictor of ED recidivism. Ongoing trials are seeking to determine whether dementia detection and point-of-care referral can reduce preventable recidivism so stay tuned.

  5. Further EBM material on

    Thank you for introducing us to EBM concepts. This was a formative experience in my interest in medicine. What would be helpful in furthering the EBM mission?

  6. Re: the evidence based medicine mission. What are the unmet needs in this area? What would be helpful in furthering the EBM mission? What skill sets could contribute to EBM or EBHP? What types of contributions are needed and useful?

  7. Dr. Worster:
    Would you have suggestions regarding areas of development for EBM/EBHP? In your opinion, what are the areas with unmet needs, or the areas where work is needed? WHat skill set should EBHP interested individuals consider acquiring to address areas of future R&D?

  8. EBHP Question on

    My interest is professional and based on the leadership you have both displayed at the McMaster course. I am interested in EBHP. My skill set is a fast learning curve and the ability to rapidly acquire subject matter expertise, as well as understanding and synthesizing complex information. How could this add value in the area of EBHP?

  9. Chris Carpenter on

    Apologies, I just saw this string of messages. Very late reply. In my opinion, the biggest priority for EBM is to provide proof that EBM works. There are a long list of criticisms pointed towards EBM, but the most compelling is that EBM is internally inconsistent. Nobody has every demonstrated that nurses or physicians who practice EBM provide more efficient, cost-effective, or effective care. This is a tall order, but one which the next generation of EBM leaders must accomplish.

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