INTRODUCTION
TEACHING TIP 1: DEMONSTRATING THE VARIABILITY IN PHYSICIAN ESTIMATION OF PRETEST PROBABILITY
When to Use This Tip?
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Understand that physicians vary in how they interpret the importance of different aspects of the history, physical exam and basic laboratory results.
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Demonstrate the variability in physician estimation of pretest probability.
The Script
A 45-year-old female on estrogen replacement therapy who has no significant past medical history presents to the emergency room at 4 am with the sudden onset of chest pain and shortness of breath. The chest pain lasted seconds, but her feeling of shortness of breath has persisted for several hours. Her physical exam is significant for an O2 saturation of 95%, pulse rate of 98 beats per minute, and an otherwise normal physical exam. Her chest x-ray is clear.
Bottom Line
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There is considerable variability in the estimation of pretest probability between clinicians for everyday clinical problems.
TIP 2: ESTIMATES OF PRETEST PROBABILITY INFLUENCE OUR INTERPRETATION OF DIAGNOSTIC TESTS AND HOW WE MANAGE OUR PATIENTS.
When to Use This Tip
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To demonstrate how the variability in estimations of pretest probability directly impact on patient management.
The Script
Bottom Line
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Variability in the estimation of pretest probability can lead to different clinical actions.
TEACHING TIP 3: EXPOSING LEARNERS TO VARIOUS CLINICAL PREDICTION RULES.
When to Use This Tip?
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To understand how to apply a clinical prediction rule in everyday practice.
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To understand how clinical prediction rules can decrease variability among physicians in clinical practice.
Preparing to Teach
1. Outcome |
○ Should be clearly defined and clinically important. If a surrogate outcome is used, it must have a definite relationship with a clinically important outcome. |
○ Blind Assessment—The presence or absence of an outcome should ideally be determined without knowledge of the status of the predictor. |
2. Predictive Variables |
○ Clear, clinically sensible, and reproducible definition of the variables. |
○ List of all variables considered, but not included in the rule. |
○ Blind Assessment—assessment of the predictors without knowledge of the outcome. |
3. Patient Population |
○ Patient characteristics that are likely to affect the performance of the rule should be described. |
4. Description of Study Site |
○ Office, clinic, ER, hospital |
5. Prospective Validation: Level of Evidence |
○ Prospectively validate the rule in a group of patients different from the group in which it was derived. |
6. Effects of Clinical Use Prospectively Measured (Impact Analysis) |
○ Are physicians actually willing to use the rule and does it affect clinical outcomes. |
7. Mathematical Techniques Described |
○ multivariate analysis |
8. Describing the Results of a Clinical Prediction Rule |
○ sensitivity, specificity, likelihood ratio, positive and negative predictive value |
9. Reproducibility |
○ Interobserver reliability of the clinical predictors |
10. Sensibility |
○ Does the rule have face validity? |
The Script
CPR | Criteria | Comments |
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Ottawa Ankle Rule4
| Ankle radiographic series required only if there is pain in the malleolar zone and one or more of the following: | – Prospectively validated in multiple settings |
– Reliably ‘rules out’ fracture (sensitivity) but cannot reliably ‘rule in’ (specificity) | ||
– Bone tenderness at posterior edge (distal 6 cm) or tip of lateral malleolus·Bone tenderness at posterior edge (distal 6 cm) or tip of medial malleolus | ||
– Inability to bear weight both immediately after the injury and in the emergency department | ||
Alcohol screening 10
| – Have you ever felt you should cut down on your drinking? | – Use in screening, not in known alcoholics |
– Have people annoyed you by criticizing your drinking? | – Rule less accurate when used immediately after direct questioning regarding alcohol use. Must ask the questions in a nonjudgmental way. | |
– Have you ever felt guilty or bad about drinking? | ||
– Have you ever had a drink first thing in the morning to steady your nerves or to get rid of a hangover? | ||
Clinical Evaluation for Predicting DVT11
| – Active Cancer (1 point) | Suspected DVTs in Emergency setting stratified into High, Medium, and Low risk based on the sum of the point system: |
– Paralysis (1 point) | – >3 high probability | |
– Recent immobilization (1 point) | – 1–2 moderate probability | |
– Local tenderness over the Deep Venous system (1 point) | – 0 low probability | |
– Entire Leg Swollen (1 point) | ||
– Calf circumference> 3 cm than other leg (1 point) | ||
– Pitting edema confined to symptomatic leg (1 point) | ||
– Collateral veins (1 point) | ||
– Alternative diagnosis as least as likely (−2 points) |
Bottom Line
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Use of a CPR narrows variability between clinicians in estimating pretest probabilities and in decision making regarding testing and treatment