Script focused deduction uses minimal information to develop and test a hypothesis. A few key pieces of information are gathered to develop your first hypothesis or the “H1”. From the H1, 2-3 questions and 2 tests are then used to support or reject the hypothesis. This is very useful for the developing therapist to establish a provisional hypothesis.
Experts use pattern recognition where 4-5 common differential presentations are compared to the patient presentation. These are the common conditions seen in clinic and they focus the subjective and objective examination on ruling in or out this condition. Script focused deduction allows the therapist to start developing pattern recognition. Over the next 8 modules we will be working on developing clinical reasoning skills starting with script focused deduction.
The next section is adapted from Jim Meadows work on script focused deduction. He uses elbow pain as an example case. In the next post we will look at the lumbar essential illness scripts.
Thin Slicing
- Using the evidence coming in about thin slicing it should be possible, especially in the less complex cases to generate H1 with the bare bones of the patient presentation.
- Using the principle of minimizing information in complex decision making
- To keep the work area clear and decrease the noise and so improve the signal
Hypothetic-deduction
- If H1 is supported from the subjective exam then only the tests making up the illness script are initially carried out.
- If H1 is refuted then the most likely hypothesis generated from this information becomes H2 and its illness script is used.
- This process is repeated until the final hypothesis is successfully tested and becomes the diagnosis.
- If no diagnosis can be made a full examination is carried out
- Typically hypothetic-deductive reasoning is done as part of the general subjective examination,
- This method minimizes incoming information by asking only questions and doing only tests on the essential illness script
- So typically only three or four questions are asked and two or three tests done
- To avoid search satisfaction bias other questions are asked and the usual differential examination is carried out but after the diagnosis has been made
- If the extension of the examination refutes the diagnosis then it should also prove the replacement diagnosis but care must be taken to avoid anchoring bias so some deliberately non-supporting questions and tests are needed
Eg. Lateral Elbow Pain
- The patient reports isolated pain on the lateral side of the elbow
- The therapist considers the tissues underlying the pain and the likelihood of each condition that can give such pain.
- Statistically the most likely condition is common extensor tendonosis and this becomes H1.
- The essential illness script for tennis elbow is accessed and the questions drawn from this; for example does using the hand or elbow cause the greatest pain.
- If the answer is gripping activities then H1 is strengthened and the next question from the ECS is asked the answer to which will either strengthen or weaken H1.
- If H1 is weakned by say pain on elbow movement rather than hand function then H2 may be articular dysfunction.
- The essential illness script for articular dysfunction is accessed and questions from it asked.
- If H2 is supported objective tests are carried out, these may be quadrant tests of the full biomechanical exam of the elbow.
- Assuming the diagnosis is upheld then questions can be asked about etiology for example, have you done anything usual recently, changed work positions or tools, do you have neck pain, are there any neurological symptoms, and null questions can be asked for example do you have pain with neck movements or positions, or shoulder movements.
- The neck and the rest of the upper limb can now be examined to see if there are any predisposing factors, you can repeat the isometric tests in various neck position etc…
In short more time can be spent on the more complex aspects of the problem (level of inflammation, etiology and contributing remote pathologies etc.) when less time has to be spent on the differential diagnosis
Strengths and Weakness
- It is simple and easy to understand
- It reduces the noise and improves the signal coming from the patient and so minimizes the potential for the clinician to become confused
- It does not work well with atypical variants and where two different pathologies are generating symptoms
- It is not as efficient nor probably as accurate as pattern recognition in the hands of an expert
Bias Correction
- Diagnostic anchoring and regression to the familiar can be reduced or eliminated by making the diagnosis a null hypothesis and try to disprove it
- A complete examination carried out once the diagnosis is made will be the final arbiter until the clinician is confident enough in their ability to diagnose.
Essential Illness Script
- This is the unique cluster of signs and symptoms that identifies the average presentation of the condition
- Usually it consists of 3-5 questions and 2 or 3 tests
- Usually if two of the subjective responses or one or two objective tests do not support the H then it needs to be replaced
Summary
The uncomplicated diagnosis should be easily available to non- experts and not a struggle
It mimics what experts do with pattern recognition, that is ask a few supporting questions and do a few tests, without the experience of expertise being required
But by completing all aspects of the examination after the diagnosis has been made it reduces bias and error
For more information here is a link to moodle for Jim Meadows manual on Script focused deduction. If not in a current course email me and I can forward you the text.