Positive Findings (Patient Has This)

SymptomsIncreased Disease Probability (Positive Likelihood Ratio)
No pain when seated7.4× (1.9-30)
Burning sensation around the buttocks, Intermittent priapism associated with walking, or both7.2× (1.6-32)
Urinary disturbance6.9× (2.7-17)
Improvement when bending forward6.4× (4.1-9.9)
Bilateral buttock or leg6.3× (3.1-13)
Neurogenic claudication3.7× (2.9-4.8)
Numbness of perineal region3.7× (1.0-13)
Improve when seated3.3× (1.4-7.7)
Exacerbation when standing up2.3× (1.8-2.8)
Bilateral plantar numbness2.2× (1.4-3.2)
Treatment for symptoms needs to be repeated every year2.0× (1.5-2.8)
Orthopedic disease2.0× (1.2-3.5)
Pain below buttocks1.4× (1.0-1.8)
Exacerbated while standing up1.2× (1.1-1.3)
Wake up to urinate at night1.2× (1.1-1.3)
Thigh1.1× (1.0-1.2)
Gluteal0.88× (0.79-0.98)
Signs on Physical ExamIncreased Disease Probability (Positive Likelihood Ratio)
Wide-based gait13× (1.9-95)
Abnormal Romberg test result4.2× (1.4-13)
Vibration deficit2.8× (1.3-6.2)
Pinprick deficit2.5× (1.1-5.5)
Age >65 (vs ≤65)2.5× (1.4-4.2)
Weakness2.1× (1.0-4.4)
Absent Achilles reflex2.1 (1.0-4.4)
No pain with flexion1.4 (1.0-2.0)
Symptoms worsened with bending forward0.48 (0.34-0.66)

Negative Findings (Patient Doesn't Have This)

SymptomsDecreased Disease Probability (Negative Likelihood Ratio)
Neurogenic claudication0.23× (0.17-0.31)
Pain below buttocks0.34× (0.13-0.88)
Thigh0.36× (0.12-1.1)
Exacerbated while standing up0.38× (0.21-0.69)
Exacerbation when standing up0.46× (0.37-0.56)
Wake up to urinate at night0.50× (0.33-0.78)
Improvement when bending forward0.52× (0.46-0.60)
Bilateral buttock or leg0.54× (0.43-0.68)
No pain when seated0.57× (0.43-0.76)
Improve when seated0.58× (0.41-0.81)
Treatment for symptoms needs to be repeated every year0.75× (0.65-0.86)
Bilateral plantar numbness0.84× (0.76-0.92)
Urinary disturbance0.88× (0.83-0.93)
Orthopedic disease0.90× (0.83-0.98)
Burning sensation around the buttocks, Intermittent priapism associated with walking, or both0.95× (0.92-0.98)
Numbness of perineal region0.97× (0.94-1.0)
Gluteal3.3× (1.2-8.8)
Signs on Physical ExamDecreased Disease Probability (Negative Likelihood Ratio)
Pain below buttocks0.34× (0.13-0.88)
Age >65 (vs ≤65)0.34× (0.19-0.61)
Thigh0.36× (0.12-1.1)
Exacerbated while standing up0.38× (0.21-0.69)
Exacerbation when standing up0.46× (0.37-0.56)
No pain with flexion0.48× (0.24-0.96)
Wake up to urinate at night0.50× (0.33-0.78)
Improvement when bending forward0.52 (0.46-0.60)
Bilateral buttock or leg0.54 (0.43-0.68)
Vibration deficit0.57 (0.40-0.82)
No pain when seated0.57 (0.43-0.76)
Improve when seated0.58 (0.41-0.81)
Wide-based gait0.60 (0.46-0.78)
Pinprick deficit0.66 (0.48-0.91)
Abnormal Romberg test result0.67 (0.51-0.87)
Weakness0.69 (0.49-0.96)
Absent Achilles reflex0.69 (0.49-0.96)
Treatment for symptoms needs to be repeated every year0.75 (0.65-0.86)
Bilateral plantar numbness0.84 (0.76-0.92)
Urinary disturbance0.88 (0.83-0.93)
Orthopedic disease0.90 (0.83-0.98)
Burning sensation around the buttocks, Intermittent priapism associated with walking, or both0.95 (0.92-0.98)
Numbness of perineal region0.97 (0.94-1.0)
Symptoms induced by having patients bend forward1.3 (1.2-1.5)
Gluteal3.3 (1.2-8.8)

Source: Suri P, Rainville J, Kalichman L, Katz JN. Does this older adult with lower
extremity pain have the clinical syndrome of lumbar spinal stenosis? JAMA. 2010
Dec 15;304(23):2628-36. doi: 10.1001/jama.2010.1833. Review. PubMed PMID:
21156951; PubMed Central PMCID: PMC3260477.

Narrative: Outcome was clinical syndrome of Lumbar Spinal Stenosis (LSS).

Caveats:


  • A characteristic clinical presentation, including neurogenic claudication, radicular pain, or both; and

  • Radiographic or anatomic LSS
  • Author: Rodrigo Kong, MD and Shahriar Zehtabchi, MD

    Published/Updated: February 25, 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!)