TIA Risk Stratification and Decision Rules

How do we decide which patients to admit and discharge in the Emergency Department?

– Transient Ischaemic Attack (TIA) is a common presentation where the clinician must decide on the disposition of the patient.

images

Is the ABCD2 Score useful in risk stratifying patients with TIA?

Perry JJ, Sharma M, Sivilotti MRL et al. Prospective validation of the ABCD2* Score for patients in the emergency department with transient ischemic attack. CMAJ. 2011 Jul 12;183(10):1137-45

* ABCD 2 Score

(Age, Blood pressure, Clinical features, Duration of symptoms and Diabetes)

Free PMC Article – http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3134721

The Study

The study by Canadian authors in Ontario Emergency Departments looked at patients presenting to the Emergency Department (ED) setting who had a rate of stroke of 1.8% at 7 days and 3.2% at 90 days.

The study was a prospective cohort study in 8 ED institutions over a 3 year period starting in 2007.  It recruited 2056 patients.  The patients were all adults (>18 years old) with a mean age of 68 years and equal gender split.

Primary outcome was stroke at 7 days and Secondary outcome was stroke at 90 days and further TIA. Inclusion criteria were a clinical diagnosis of TIA or ‘minor stroke’ as judged by the treating doctors on presentation to the ED.

The authors looked at various cut points of the ABCD2 score (a score of 2 and a score of 5) and made calculations of the sensitivity and accuracy of the scoring system.  The treating physicians calculated the ABCD2 score (this was later checked by a second physician and stroke nurse.)

Results

The authors state that this is the first time that the ABCD2 score has been prospectively validated.

The study found that the widely used ABCD2 Score is an inaccurate predictor of short-term stroke risk after transient ischemic attack (TIA).   An ABCD2 score of more than 2 resulted in sensitivity of 94.7% for stroke at 7 days and a specificity of only 12.5%. The accuracy of the ABCD2 score as calculated by physician was also poor.

Upon reviewing the literature, I noted that the same investigators found that Emergency doctors were willing to use a decision rule to triage patients, use clinical imaging and where appropriate manage TIA patients as outpatients.  Despite a willingness to use these tools, this study specifically raises concerns about the validity of this particular rule in predicting outcome.

Strengths

The strength of this study was that it was a large multicentre study and it used a prospective approach.

Conclusions

Given that this study was carried out in a ‘real world’ environment and used a widely used decision tool the study is useful to ED doctors making disposition decisions about TIA patients.  This study goes some way to show that this** decision tool alone has limited value in risk stratifying patients due to its limited accuracy.   While a more sensitive rule would be useful it appears that in the care of TIA patients that we should be cautious about using the ABCD score and instead use clinical skills, experience and consult carefully with a stroke specialist.

Musings

**Note that some ED physicians (especially Dave Schriger) have criticised the use of decision rules as akin to ‘cookbook medicine’: http://embundles.files.wordpress.com/2012/03/piis0196064411015381.pdf .

While this probably more of a philosophical debate about the practice of Emergency Medicine in the wider sense, it is important to be aware that these tools have limitations as reflected paper by Perry.  Incidentally, I note that Perry is in the process of developing a Subarachnoid Haemorrhage ‘rule out’ tool (so it appears he favours the use of decision tools).

Personally, I think the many tools are great teaching aids for basic principles and also a useful check list when you are tired at 3 o’clock in the morning.  However, the final decision comes down to your experience and clinical skills in combination with validated tools in order to manage the risk of making disposition decisions in a timely manner.

IMG_3504


2 thoughts on “TIA Risk Stratification and Decision Rules

Comments are closed.