|Risk Factors||Increased Disease Probability (Positive Likelihood Ratio)|
|History of Atrial fibrillation||4.1× (2.5-6.6)|
|History of Coronary artery bypass grafting||2.8× (1.3-5.8)|
|History of Myocardial infarction||2.2× (1.4-3.5)|
|History of Diabetes mellitus||2.0× (1.3-3.2)|
|History of Coronary artery disease||2.0× (1.5-2.6)|
|History of Angina||1.7× (1.0-2.5)|
|History of Hypertension||1.2× (0.95-1.5)|
|Symptoms||Increased Disease Probability (Positive Likelihood Ratio)|
|Nocturnal cough||0.93× (0.73-1.2)|
|Signs||Increased Disease Probability (Positive Likelihood Ratio)|
|3rd heart sound (ventricullar filling gallop)||57.0× (7.6-425)|
|Lower extremity edema||2.7× (2.2-3.5)|
|Hepatic congestion||2.4× (1.2-4.7)|
|Enlarged heart||1.6× (0.43-6.2)|
|Other||Increased Disease Probability (Positive Likelihood Ratio)|
|Clinician's Gestalt||9.9× (5.3-18)|
|CXR Findings||Increased Disease Probability (Positive Likelihood Ratio)|
|Pleural effusion(s)||4.6× (2.6-8.0)|
|EKG Findings||Increased Disease Probability (Positive Likelihood Ratio)|
|Atrial fibrillation||6.0× (3.4-10.0)|
|Ischemic ST-T waves||4.6× (2.4-8.7)|
|Q waves||3.1× (1.8-5.5)|
|BNP Levels||Increased Disease Probability (Positive Likelihood Ratio)|
|BNP ≥100 pg/ml||4.1 (3.3-5.0)|
|Risk Factors||Decreased Disease Probability (Negative Likelihood Ratio)|
|Coronary artery disease||0.67× (0.54-0.84)|
|Atrial fibrillation||0.74× (0.63-0.85)|
|Myocardial infarction||0.84× (0.74-0.96)|
|Diabetes mellitus||0.85× (0.74-0.97)|
|Coronary artery bypass grafting||0.92× (0.84-0.99)|
|Symptoms||Decreased Disease Probability (Negative Likelihood Ratio)|
|Nocturnal cough||1.1× (0.85-1.4)|
|Signs||Decreased Disease Probability (Negative Likelihood Ratio)|
|Lower extremity edema||0.41× (0.30-0.57)|
|3rd heart sound (ventricullar filling gallop)||0.83× (0.75-0.91)|
|Hepatic congestion||0.91× (0.84-1.0)|
|Enlarged heart||0.99× (0.95-1.0)|
|Other||Decreased Disease Probability (Negative Likelihood Ratio)|
|Clinician's Gestalt||0.65× (0.55-0.77)|
|CXR Findings||Decreased Disease Probability (Negative Likelihood Ratio)|
|Pleural effusion(s)||0.78× (0.69-0.89)|
|EKG Findings||Decreased Disease Probability (Negative Likelihood Ratio)|
|Atrial fibrillation||0.73× (0.63-0.84)|
|Ischemic ST-T waves||0.83× (0.74-0.93)|
|Q waves||0.84× (0.75-0.94)|
|BNP Levels||Decreased Disease Probability (Negative Likelihood Ratio)|
|BNP ≥100 pg/ml||0.09× (0.04-0.19)|
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!)
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