ReMed 2018 Remed 5 - Histoire de la Médecine | Page 14

Sciences de la Santé

Now that we have all the LRs, the final step
is to know how to use them. With some complicated
formulas and statistical methods, which we will not
demonstrate here, we calculate the shift in probability
related to each likelihood ratio. We obtain the follow-
ing results.
This means that if a sign has a likelihood ratio of 10,
your patient, who has the positive sign, has 45% more
chances of having the disease. As well, if your patient
has a sign whose is 0.2, he has 30% less chances of
having the disease.
If we apply these to our example, we obtain this:
Dr. McGee proposes to simplify the results and to con-
sider only values above 3, which correspond to a 20%
increase in probability, and below 0.3, which corre-
spond to a 25% decrease in probability 14 . In our case
the results are much more simple :

Now as a clinician, if your patient has Fluid
wave and Edema, you know that he has 25% + 30% =
55% more chances of having an ascites. On the oth-
er hand, if your patient doesn’t have Edema and has
Flank tympany, then he has 55% less chances of hav-
ing Ascites.

Let’s apply this to our confusing example; remem-
ber we had Bulging flanks (+ 15%), shifting dullness (+ 15%),
fluid wave (+30) and an absence of all the other features
(- 50%). Thus, our patient has 10% more chances of having
ascites by the findings of physical examination alone.
Of course we should incorporate this in a whole pro-
cess of reasoning including the patient’s history and
para-clinical features but it is a simple and fast way to
rationalize data and make the most practical use of it in
order to save time and money and help you know what
is really going on in your patient.
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Printemps 2018
In fact, if you can master this, it would be as if you per-
sonally examined all the patients in the studies and
remembered how accurate the bedside exam was for
each of them!
Physical examination assessment and teaching
Teaching and evaluating physical examination skills
is a very challenging issue. Assuming that the teacher
is himself qualified and skilled enough, it is very hard
for him to teach his techniques, and even harder to
distinguish among his students those who have real-
ly mastered them. Have you tried to teach cardiac or
pulmonary auscultation abnormalities to a student? It
is easy to tell him that this patient has a pneumonia
and that he should hear crackles, and he will often
tell you that he had indeed listened to them, but how
can you be sure of that? And even if you are, how can
you be sure he will recognize crackles next time he
hears them? Even worse are physical signs that do not
obey the dichotomous answer present/absent. How to
teach your student that this deep tendon reflex or this
mitral valve S1 sound is exaggerated or diminished?

Here again we do not pretend to give solu-
tions, but we must point out some major mistakes
present in the medical curriculum. First, many studies
show a very big lack in new generation doctors skills 15,
16
and This is due to the very little attention given by
medical curriculum to clinical examination, even in
traditional programs, and this is way far from being
resolved by simple lecture courses 16 . The only method
that seems reliable is more hours of practice and more
patient-focused training sessions. The willingness of
going in contact with patients and examine them
must be taught and established in very early stages
of medical curriculum, otherwise future doctors would
get used to being away from patients and remain like
that for the rest of their careers.
Perhaps the best illustration of the commitment of a
teacher is the famous sentence of Baily, while asking
his students to perform a rectal examination: “If you
don’t put your finger in, you might put your foot in it”.

Another problem of physical examination
teaching is the lack of a precise organized plan and
check-list. Of course techniques and tricks are taught
everywhere, but very few textbooks provide general
examination sequences. This is due to the idea that a
physician should build his own sequence, however we
believe (from experience) that most of medical stu-
dents get confused and don’t know how to start their
physical examination and whether they performed all
the techniques required or not. We invite you to take a
look at this study showing most physical examination
mistakes among young physicians 17 . One can easily
notice that most of these techniques are well known
and quite easy to master, physicians simply forget to