We welcome the publication of Medow and Lucey in the December issue, describing a qualitative approach to Bayes' theorem [1]. Especially because the authors provide a new impulse to the development of clinician-friendly strategies for teaching clinical decision making skills.
However, the approach proposed by the authors is not new. We reported a didactic model based on a visual representation of B...
We welcome the publication of Medow and Lucey in the December issue, describing a qualitative approach to Bayes' theorem [1]. Especially because the authors provide a new impulse to the development of clinician-friendly strategies for teaching clinical decision making skills.
However, the approach proposed by the authors is not new. We reported a didactic model based on a visual representation of Bayesian logic on a logarithmic scale eight years ago in peer-reviewed journals [ 2-4]. Our logical frame is also categorical and similar to the one proposed here, but it is more elaborate: it allows for the extremes of the probability scale, it provides more test power categories, and it covers asymmetry of test results.
The authors report a major limitation of their model: it applies to the intermediate range of probabilities (10-90), leaving the very high post test probabilities often at stake in specialist care and the very low concerned in general practice to the discretion of the clinician. In our model, using a log odds scale, findings with a "weak" power allow to advance or regress half step towards or away from diagnosis, "good" arguments one step, "strong" arguments one and a half and "very strong" two steps. In the author's model only two categories of test values are considered, good and very good. In case of weaker tests, the authors propose to change the probability category scale. Our model offers four categories of power of tests, reportedly also used by Alan Turing 50 years ago, corresponding to the log10 of the likelihood ratio rounded to half the unit [5].
Finally, their model somehow suggests symmetry of test results, a major misconception of junior clinicians. This symmetry applies to their example of a nuclear stress test, but not e.g., to D-dimers which are useful to exclude a pulmonary embolism, but add almost nothing for confirmation of the diagnosis.
We apply this approach for more than a decade in under and post graduate teaching and in clinical decision making workshops in different countries of Europe, Asia, Africa and South America with enthusiastic acceptance by trainees, but the effect of training with this approach still needs thorough assessment [6].
References
[1] Medow MA, Lucey CR. A qualitative approach to Bayes' theorem. Evid Based Med 2011;16(6):163-167.
[2] Van Puymbroeck H, Remmen R, Denekens J, et al. Teaching problem solving and decision making in undergraduate medical education: an instructional strategy. Med Teach 2003;25(5):547-550.
[3] Van Den Ende J, Bisoffi Z, Van Puymbroek H, et al. Bridging the gap between clinical practice and diagnostic clinical epidemiology: pilot experiences with a didactic model based on a logarithmic scale. J Eval Clin Pract 2007;13(3):374-380.
[4] Van Den Ende J, Moreira J, Basinga P, et al. The trouble with likelihood ratios. Lancet 2005;366(9485):548.
[5] Good I. AM Turing's statistical work in world war II. (Studies in the history of probability and statistics XXXVII). Biometrika 1979;66(2):393-396.
[6] Moreira J, Bisoffi Z, Narvaez A, et al. Bayesian clinical reasoning: does intuitive estimation of likelihood ratios on an ordinal scale outperform estimation of sensitivities and specificities? J Eval Clin Pract 2008;14(5):934-940.
The dorsal horns are not merely passive transmission stations but
sites at which dynamic activities (inhibition, excitation and modulation)
occur. [18]
Via a series of filters and amplifiers, the nociceptive message is
integrated and analysed in the cerebral cortex, with interconnections with
various areas. [1]
The processing of pain takes place in an integrated matrix throughout...
The dorsal horns are not merely passive transmission stations but
sites at which dynamic activities (inhibition, excitation and modulation)
occur. [18]
Via a series of filters and amplifiers, the nociceptive message is
integrated and analysed in the cerebral cortex, with interconnections with
various areas. [1]
The processing of pain takes place in an integrated matrix throughout
the neuroaxis and occurs on at least three levels, at peripheral, spinal,
and supraspinal sites. [9]
Knowledge of the modalities of pain control is essential to correctly
adapt treatment strategies (drugs, neurostimulation, psycho-behavioural
therapy, etc.).
Dysfunction of pain control systems causes neuropathic pain. [1]
Spinal Cord Stimulation modalities evolved from the gate-control
theory postulating a spinal modulation of noxious inflow. [16] [2] [7]
[11] [12] [15] [17] [20] [22] [23] [24] [25] [26]
It has been demonstrated in multiple studies that dorsal horn
neuronal activity caused by peripheral noxious stimuli could be inhibited
by concomitant stimulation of the dorsal columns. [8]
Pain relief was more prominent at pain ascending through C fibers
than pain ascending through Adelta fibers [21]
Many theories on the mechanism of action of Spinal Cord Stimulation
have been suggested, including activation of gate control mechanisms,
conductance blockade of the spinothalamic tracts, activation of
supraspinal mechanisms, blockade of supraspinal sympathetic mechanisms,
and activation or release of putative neuromodulators. [14]
At present, Spinal Cord Stimulation is a well established form of
treatment for failed back surgery syndrome, complex regional pain
syndromes (CRPS), low back pain with radiculopathy and refractory pain due
to ischemia. [4] [3] [8] [13]
Stimulation produced analgesia can provide a level of analgesia and
efficacy that is unattainable by other treatment modalities. [19]
Spinal Cord Stimulation for the treatment of chronic pain is cost-
effective when used in the context of a pain treatment continuum. [14]
Precise subcutaneous field stimulation is targeted to specific areas
of neuropathic pain. [6]
We aim at attenuation or blockade of pain through intervention at the
periphery, by activation of inhibitory processes that gate pain at the
spinal cord and brain. [9]
Segmental noxious stimulation produces a stronger analgesic effect
than segmental innocuous stimulation. [10]
That is exactly what intradermal sterile water or subcutaneous saline
injections do!
Chloride, used in subcutaneous "sham" injections, independently
regulates the pain pathway. [5]
In these studies there was no valid control group receiving sham
injections.
In the past, other researchers, in similar studies, have also had
difficulties in blinding and comparing with control groups. [4]
These RCTs simply compared an established therapeutic intervention to
another established therapeutic intervention.
References
[1] Labat JJ, Robert R, Delavierre D, et al. Anatomy and physiology of chronic pelvic and perineal pain. Prog Urol 2010;20(12):843-52. Epub 2010 Oct 20.
[2] Moharic M, Burger H. Effect of transcutaneous electrical nerve stimulation on sensation
thresholds in patients with painful diabetic neuropathy: an observational
study. Int J Rehabil Res 2010;33(3):211-7.
[3] Shrivastav M, Musley S. Spinal cord stimulation for complex regional pain syndrome.
Conf Proc IEEE Eng Med Biol Soc 2009;2009:2033-6.
[4] Kunnumpurath S, Srinivasagopalan R, Vadivelu N. Spinal cord stimulation: principles of past, present and future practice:
a review. J Clin Monit Comput 2009;23(5):333-9.
[5] Price TJ, Cervero F, Gold MS, et al. Chloride regulation in the pain pathway. Brain Res Rev 2009;60(1):149-70. Epub 2008 Dec 31.
[6] Henderson JM. Peripheral nerve stimulation for chronic pain. Curr Pain Headache Rep 2008;12(1):28-31.
[7] Handwerker HO. From Descartes to fMRI. Pain theories and pain concepts. Schmerz 2007;21(4):307-10, 312-7.
[9] DeLeo JA. Basic science of pain. J Bone Joint Surg Am 2006;88 Suppl 2:58-62.
[10] Defrin R, Ariel E, Peretz C. Segmental noxious versus innocuous electrical stimulation for chronic pain
relief and the effect of fading sensation during treatment. Pain 2005;115(1-2):152-60.
[11] Craig AD. Pain mechanisms: labeled lines versus convergence in central processing. Annu Rev Neurosci 2003;26:1-30. Epub 2003 Mar 6.
[12] Staal JB, Hlobil H, van Tulder MW, et al. Return-to-work interventions for low back pain: a descriptive review of
contents and concepts of working mechanisms. Sports Med 2002;32(4):251-67.
[14] Krames E. Spinal Cord Stimulation: Indications, Mechanism of Action, and Efficacy. Curr Rev Pain 1999;3(6):419-426.
[15] Costentin J. Pain and its main transmitters. Ann Pharm Fr 2000;58(2):77-83.
[16] Meyerson BA, Linderoth B. Mechanisms of spinal cord stimulation in neuropathic pain. Neurol Res 2000;22(3):285-92.
[17] Yaksh TL. Regulation of spinal nociceptive processing: where we went when we
wandered onto the path marked by the gate. Pain 1999;Suppl 6:S149-52.
[18] Melzack R. From the gate to the neuromatrix. Pain 1999;Suppl 6:S121-6.
[19] Stanton-Hicks M, Salamon J. Stimulation of the central and peripheral nervous system for the control
of pain. J Clin Neurophysiol. 1997;14(1):46-62.
[20] Humphries SA, Johnson MH, Long NR. An investigation of the gate control theory of pain using the experimental
pain stimulus of potassium iontophoresis. Percept Psychophys 1996 ;58(5):693-703.
[21] Kakigi R, Watanabe S. Pain relief by various kinds of interference stimulation applied to the
peripheral skin in humans: pain-related brain potentials following CO2
laser stimulation. J Peripher Nerv Syst. 1996;1(3):189-98.
[22] Davis P. Pain: opening up the gate control theory. Nurs Stand. 1993;7(45):25-7.
[23] Cambier J. Gate control of the nociceptive message: applications to the treatment of pain. Bull Acad Natl Med 1989;173(7):855-60; discussion 860-1.
[24] Benabid AL, Henriksen SJ, McGinty JF, et al. Thalamic nucleus ventro-postero-lateralis inhibits nucleus
parafascicularis response to noxious stimuli through a non-opioid pathway. Brain Res 1983;280(2):217-31.
[25] Malow RM, Dougher MJ. A signal detection analysis of the effects of transcutaneous stimulation
on pain. Psychosom Med. 1979 Mar;41(2):101-8.
[26] Goldman DE. Gate control of ion flux in axons. J Gen Physiol 1965;48:SUPPL:75-7.
Although the accuracy of a mercury sphygmomanometer can be debated,
automatic and semi-automatic devices which inflate the cuff often do so to
well above the systolic pressure and can cause patients considerable
discomfort even when an appropriate cuff size has been used. These devices
frequently re-inflate for a variety of reasons, but out of control of the
operator who is waiting for a reading.
Although the accuracy of a mercury sphygmomanometer can be debated,
automatic and semi-automatic devices which inflate the cuff often do so to
well above the systolic pressure and can cause patients considerable
discomfort even when an appropriate cuff size has been used. These devices
frequently re-inflate for a variety of reasons, but out of control of the
operator who is waiting for a reading.
Anecdotally, I have had several patients request I use what they call
the "old fashioned" mercury sphygmomanometer at future consultations.
It would not be surprising to find that the "error" rate in blood
pressure determinations with the "old fashioned" sphygmomanometer was due,
in part, to a faulty technique by the individuals taking the blood
pressures. Remarkably, little or no time is spent in teaching medical
students the proper technique for blood pressure determination including
the appropriate cuff size to use, the various audible phases, etc. One
ca...
It would not be surprising to find that the "error" rate in blood
pressure determinations with the "old fashioned" sphygmomanometer was due,
in part, to a faulty technique by the individuals taking the blood
pressures. Remarkably, little or no time is spent in teaching medical
students the proper technique for blood pressure determination including
the appropriate cuff size to use, the various audible phases, etc. One
cannot determine if there is an exaggerated second phase of Karotkoff
sounds, which is an indicator of the presence of atherosclerotic disease,
with an electronic blood pressure apparatus. Neither can one determine the
presence of a pulsus paradoxicus with an electronic device. The relegation
of the stethoscope to the rubbish bin or museum was predicted decades ago
and has not yet taken place. I, for one, will continue to use my
stethoscope and take my patients' blood pressures with a manual
sphygmomanometer, thank you.
Dear editor,
We welcome the publication of Medow and Lucey in the December issue, describing a qualitative approach to Bayes' theorem [1]. Especially because the authors provide a new impulse to the development of clinician-friendly strategies for teaching clinical decision making skills.
However, the approach proposed by the authors is not new. We reported a didactic model based on a visual representation of B...
Dear Editors,
The dorsal horns are not merely passive transmission stations but sites at which dynamic activities (inhibition, excitation and modulation) occur. [18]
Via a series of filters and amplifiers, the nociceptive message is integrated and analysed in the cerebral cortex, with interconnections with various areas. [1]
The processing of pain takes place in an integrated matrix throughout...
Although the accuracy of a mercury sphygmomanometer can be debated, automatic and semi-automatic devices which inflate the cuff often do so to well above the systolic pressure and can cause patients considerable discomfort even when an appropriate cuff size has been used. These devices frequently re-inflate for a variety of reasons, but out of control of the operator who is waiting for a reading.
Anecdotally, I...
It would not be surprising to find that the "error" rate in blood pressure determinations with the "old fashioned" sphygmomanometer was due, in part, to a faulty technique by the individuals taking the blood pressures. Remarkably, little or no time is spent in teaching medical students the proper technique for blood pressure determination including the appropriate cuff size to use, the various audible phases, etc. One ca...
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