Positive Findings (Patient Has This)

Risk FactorsIncreased Disease Probability (Positive Likelihood Ratio)
Age <=60y1.7× (1.4-1.9)
Alcohol consumption1.6× (1-2.5)
Male1.2× (1.1-1.3)
Hypertension1.1× (1.0-1.2)
Cigarette smoking0.79× (0.45-1.4)
Diabetes mellitus0.64× (0.43-0.95)
Prior stroke0.59× (0.17-2.0)
Hyperlipidemia0.48× (0.2-1.1)
Coronary artery disease0.44× (0.31-0.61)
Atrial fibrillation0.44× (0.25-0.78)
Peripheral artery disease0.41× (0.2-0.83)
Prior TIA0.34× (0.18-0.65)
SymptomsIncreased Disease Probability (Positive Likelihood Ratio)
Seizures w/ neurological deficit4.7× (1.6-14)
Vomiting3.0× (1.7-5.5)
Headache2.9× (1.7-4.8)
Loss of consciousness2.6× (1.6-4.2)
Acute onset deficit0.65 (0.52-0.81)
SignsIncreased Disease Probability (Positive Likelihood Ratio)
Kernig's or Brudzinski's or both8.2× (0.44-150)
LOC: coma6.2× (3.2-12)
Neck stiffness5.0× (1.9-12.8)
Diastolic BP >110 mmHg4.3× (1.4-14)
LOC: drowsy2.0× (1.0-3.9)
Plantar response: both extensor1.8× (0.99-3.4)
Plantar response: single extensor1× (0.87-1.2)
Hemiparesis0.96× (0.9-1.0)
Plantar response: both flexor0.45× (0.25-0.81)
LOC: alert0.35× (0.24-0.5)
Cervical bruit0.12× (0.03-0.47)
Labs/StudiesIncreased Disease Probability (Positive Likelihood Ratio)
Xanthochromia in CSF15× (7.7-29)
Atrial fibrillation on ECG0.19× (0.06-0.59)
OtherIncreased Disease Probability (Positive Likelihood Ratio)
Clinician's Gestalt6.2× (4.2-9.3)

Negative Findings (Patient Doesn't Have This)

Risk FactorsDecreased Disease Probability (Negative Likelihood Ratio)
Age <=60y0.71× (0.63-0.82)
Alcohol consumption0.75× (0.51-1.1)
Male0.85× (0.77-0.94)
Hypertension0.88× (0.77-1.01)
Diabetes mellitus1.1× (1.0-1.2)
Prior stroke1.1× (0.88-1.4)
Hyperlipidemia1.1× (1.1-1.1)
Coronary artery disease1.1× (1.0-1.3)
Atrial fibrillation1.1× (1.05-1.1)
Peripheral artery disease1.1× (1.0-1.1)
Prior TIA1.2× (1.1-1.3)
Cigarette smoking1.2× (0.79-1.8)
SymptomsDecreased Disease Probability (Negative Likelihood Ratio)
Vomiting0.73× (0.59-0.91)
Headache0.66× (0.56-0.77)
Loss of consciousness0.65× (0.52-0.82)
Seizures w/ neurological deficit0.93× (0.9-0.96)
Acute onset deficit1.7× (1.4-2.1)
SignsDecreased Disease Probability (Negative Likelihood Ratio)
Diastolic BP >110 mmHg0.59× (0.93-0.89)
Neck stiffness0.83× (0.75-0.92)
Kernig's or Brudzinski's or both0.87× (0.73-1.0)
Hemiparesis1.1× (1.0-1.2)
Cervical bruit1.1× (1.0-1.1)
Labs/StudiesDecreased Disease Probability (Negative Likelihood Ratio)
Xanthochromia in CSF0.31× (0.19-0.49)
Atrial fibrillation on ECG1.2× (1.0-1.5)
OtherDecreased Disease Probability (Negative Likelihood Ratio)
Clinician's Gestalt0.28× (0.20-0.39)

Source: Runchey S, McGee S. Does this patient have a hemorrhagic stroke?: clinical
findings distinguishing hemorrhagic stroke from ischemic stroke. JAMA. 2010 Jun 9;303(22):2280-6. doi: 10.1001/jama.2010.754. Review. PubMed PMID: 20530782.

Narrative: Clinical exam findings help form an impression of hemorrhage vs ischemic stroke but head CT (when possible) is the best test to rapidly distinguish the stroke subtype.

Caveats:


  • Authors' RCE study selection criteria excluded those that enrolled patients with subarachnoid hemorrhage (which will present with some similar findings of hemorrhagic stroke).

  • Diagnostic value of Xanthochromia was only reported by one study (Britton et al., Acta Med Scand 1983), which determined xanthochromia by both visual assessment and spectophotometry for comparison. LRs calculated by each technique were almost the same.

Author: Khaled Hassan, MD and Shahriar Zehtabchi, MD

Published/Updated: April 8, 2013

LR, pretest probability and posttest (or posterior) probability are daunting terms that describe simple concepts that we all intuitively understand.

Let's start with pretest probability: that's just a fancy term for my initial impression, before we perform whatever test it is that we're going to use.

For example, a patient with prior stents comes in sweating and clutching his chest in agony, I have a pretty high suspicion that he's having an MI – let's say, 60%. That is my pretest probability.

He immediately gets an ECG (known here as the "test") showing an obvious STEMI.

Now, I know there are some STEMI mimics, so I'm not quite 100%, but based on my experience I'm 99.5% sure that he's having an MI right now. This is my posttest probability - the new impression I have that the patient has the disease after we did our test.

And likelihood ration? That's just the name for the statistical tool that converted the pretest probability to the posttest probability - it's just a mathematical description of the strength of that test.

Using an online calculator, that means the LR+ that got me from 60% to 99.5% is 145, which is about as high an LR you can get (and the actual LR for an emergency physician who thinks an ECG shows an obvious STEMI).

(Thank you to Seth Trueger, MD for this explanation!)