Positive Findings (Patient Has This)

Risk FactorsIncreased Disease Probability (Positive Likelihood Ratio)
History of Heart Failure5.8× (4.1-8.0)
History of Myocardial infarction3.1× (2.0-4.9)
History of Coronary artery disease1.8× (1.1-2.8)
History of Dyslipidemia1.7× (0.43-6.9)
History of Diabetes mellitus1.7× (1.0-2.7)
History of Hypertension1.4× (1.1-1.7)
History of Smoking0.84× (0.58-1.2)
History of COPD0.81× (0.60-1.1)
SymptomsIncreased Disease Probability (Positive Likelihood Ratio)
Paroxysmal nocturnal dyspnea2.6× (1.5-4.5)
Orthopnea2.2× (1.2-3.9)
Edema2.1× (0.92-5.0)
Dyspnea on exertion1.3× (1.2-1.4)
Fatigue and weight gain1.0× (0.74-1.4)
Cough0.93× (0.70-1.2)
SignsIncreased Disease Probability (Positive Likelihood Ratio)
3rd heart sound (ventricullar filling gallop)11× (4.9-25.0)
Abdominojugular reflux6.4× (0.81-51.0)
JVD5.1× (3.2-7.9)
Rales2.8× (1.9-4.1)
Any murmur2.6× (1.7-4.1)
Lower extremity edema2.3× (1.5-3.7)
Valsalva maneuver2.1× (1.0-4.2)
SBP <100 mmHg2.0× (0.60-6.6)
4th heart sound (atrial gallop)1.6× (0.47-5.5)
SBP >= 150 mmHg1.0× (0.69-1.6)
Wheezing0.52× (0.04-2.9)
OtherIncreased Disease Probability (Positive Likelihood Ratio)
Clinician's Gestalt4.4× (1.8-10.0)
CXR FindingsIncreased Disease Probability (Positive Likelihood Ratio)
Pulmonary venous congestion12.0× (6.8-21.0)
Interstitial edema12.0× (5.2-27.0)
Alveolar edema6.0× (2.2-16.0)
Cardiomegaly3.3× (2.4-4.7)
Pleural effusion(s)3.2× (2.4-4.3)
Any edema3.1× (0.60-16.0)
Pneumonia0.50× (0.29-0.87)
Hyperinflation0.38× (0.20-0.69)
EKG FindingsIncreased Disease Probability (Positive Likelihood Ratio)
Atrial fibrillation3.8× (1.7-8.8)
New T-wave changes3.0× (1.7-5.3)
Any abnormal finding2.2× (1.6-3.1)
ST elevation1.8× (0.80-4.0)
ST depression1.7× (0.97-2.9)
BNP LevelsIncreased Disease Probability (Positive Likelihood Ratio)
≥2504.6× (2.6-8.0)
≥2003.7× (2.6-5.4)
≥1503.1× (2.1-4.5)
Clinical judgement or BNP ≥100 pg/ml3.1× (2.8-3.5)
≥1002.7× (2.0-3.9)
≥501.7× (1.2-2.6)

Negative Findings (Patient Doesn't Have This)

Risk FactorsDecreased Disease Probability (Negative Likelihood Ratio)
History of Heart Failure0.45× (0.38-0.53)
History of Myocardial infarction0.69× (0.58-0.82)
History of Coronary artery disease0.68× (0.48-0.96)
History of Hypertension0.71× (0.55-0.93)
History of Dyslipidemia0.89× (0.69-1.1)
History of Diabetes mellitus0.86× (0.73-1.0)
History of Smoking1.4× (0.58-3.6)
History of COPD1.1× (0.95-1.4)
SymptomsDecreased Disease Probability (Negative Likelihood Ratio)
Dyspnea on exertion0.48× (0.35-0.67)
Edema0.64× (0.39-1.1)
Orthopnea0.65× (0.45-0.92)
Paroxysmal nocturnal dyspnea0.70× (0.54-0.91)
Fatigue and weight gain0.99× (0.85-1.1)
Cough1.0× (0.87-1.3)
SignsDecreased Disease Probability (Negative Likelihood Ratio)
Valsalva maneuver0.41× (0.17-1.0)
Rales0.51× (0.37-0.70)
Lower extremity edema0.64× (0.47-0.87)
JVD0.66× (0.57-0.77)
Abdominojugular reflux0.79× (0.62-1.0)
Any murmur0.81× (0.73-0.90)
3rd heart sound (ventricullar filling gallop)0.88× (0.83-0.94)
SBP <100 mmHg0.97× (0.91-1.0)
4th heart sound (atrial gallop)0.98× (0.93-1.0)
SBP ≥ 150 mmHg0.99× (0.84-1.2)
Ascities1.0× (0.99-1.1)
Wheezing1.3× (1.1-1.7)
OtherDecreased Disease Probability (Negative Likelihood Ratio)
Clinician's Gestalt0.45× (0.28-0.73)
CXR FindingsDecreased Disease Probability (Negative Likelihood Ratio)
Cardiomegaly0.33× (0.23-0.48)
Any edema0.38× (0.11-1.3)
Pulmonary venous congestion0.48× (0.28-0.83)
Interstitial edema0.68× (0.54-0.85)
Pleural effusion(s)0.81× (0.77-0.85)
Alveolar edema0.95× (0.93-0.97)
Pneumonia1.0× (1.0-1.1)
Hyperinflation1.1× (1.0-1.1)
EKG FindingsDecreased Disease Probability (Negative Likelihood Ratio)
Any abnormal finding0.64× (0.47-0.88)
Atrial fibrillation0.79× (0.65-0.96)
New T-wave changes0.83× 0.74-0.92)
ST elevation0.98× (0.94-1.0)
ST depression0.95× (0.90-1.0)
BNP LevelsDecreased Disease Probability (Negative Likelihood Ratio)
≥500.06× (0.03-0.12)
≥800.06× (0.03-0.13)
Clinical judgement or BNP ≥100 pg/ml0.09× (0.06-0.11)
≥1000.11× (0.07-0.16)
≥2000.11× (0.07-0.18)
≥2500.14× (0.06-0.33)
≥1500.15× (0.11-0.21)

Source: Wang CS, FitzGerald JM, Schulzer M, Mak E, Ayas NT. Does this dyspneic patient
in the emergency department have congestive heart failure? JAMA. 2005 Oct 19;294(15):1944-56. Review. PubMed PMID: 16234501.

Narrative: A low BNP might be helpful in ruling out CHF if the pre-test probability is equivocal. However, if pretest probability for CHF is low and BNP is above threshhold, BNP would not be helpful in ruling in CHF. In other words, very low BNP values in patients with low probability of heart failure and very high BNP values in patients with high probability of the disease can confirm clinical suspicions.


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!)