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Probabilistic-causal analysis

From these premises it is clear that the clinical diagnosis is made using the so-called hypothetical-deductive method referred to as DN[1] (deductive-nomological model[2]). But this is not realistic, since the medical knowledge used in clinical decision-making hardly contains causal deterministic laws to allow causal explanations and, hence, to formulate clinical diagnoses, among other things in the specialist context. Let us try to analyse again the case of our Mary Poppins, this time trying a probabilistic-causal approach.

Let us consider a number of individuals including people who report Orofacial Pain who generally have bone degeneration of the Temporomandibular Joint. However, there may also be other apparently unrelated causes. We must mathematically translate the 'relevance' that these causal uncertainties have in determining a diagnosis.

The casual relevance

To do this we consider the degree of causal relevance of an event with respect to an event where:

  • = patients with bone degeneration of the temporomandibular joint.
  • = patients reporting orofacial pain.
  • = patients without bone degeneration of the temporomandibular joint.

We will use the conditional probability , that is the probability that the event occurs only after the event has already occurred.

With these premises the causal relevance of the sample of patients is:

where

indicates the probability that some people (among taken into consideration) suffer from Orofacial Pain caused by bone degeneration of the Temporomandibular Joint,

while

indicates the probability that other people (always among taken into consideration) suffer from Orofacial Pain conditioned by something other than bone degeneration of the Temporomandibular Joint.

Since all probability suggest that is a value between and , the parameter  will be a number that is between and .

The meanings that we can give to this number are as follows:

  • we have the extreme cases (which in reality never occur) which are:
  • indicating that the only cause of orofacial pain is bone degeneration of the TMJ,
  • which indicates that the cause of orofacial pain is never bone degeneration of the TMJ but is something else,
  •  indicating that the probability that orofacial pain is caused by bone degeneration of the TMJ or otherwise is exactly the same,
  • and the intermediate cases (which are the realistic ones)
  • indicating that the cause of orofacial pain is more likely to be bone degeneration of the TMJ,
  • which indicates that the cause of orofacial pain is more likely not bone degeneration of the TMJ.


Second Clinical Approach

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So be it then the probability of finding, in the sample of our people, individuals who present the elements belonging to the aforementioned set

In order to take advantage of the information provided by this dataset, the concept of partition of causal relevance is introduced:

The partition of causal relevance

Always be the number of people we have to conduct the analyses upon, if we divide (based on certain conditions as explained below) this group into subsets with , a cluster is created that is called a "partition set" :

where with the symbolism it indicates that the subclass is contained in .

The partition , in order for it to be defined as a partition of causal relevance, must have these properties:

  1. For each subclass the condition must apply ie the probability of finding in the subgroup a person who has the symptoms, clinical signs and elements belonging to the set . A causally relevant partition of this type is said to be homogeneous.
  2. Each subset must be 'elementary', i.e. it must not be further divided into other subsets, because if these existed they would have no causal relevance.

Now let us assume, for example, that the population sample , to which our good patient Mary Poppins belongs, is a category of subjects aged 20 to 70. We also assume that in this population we have those who present the elements belonging to the data set which correspond to the laboratory tests mentioned above and precisa in 'The logic of classical language'.

Let us suppose that in a sample of 10,000 subjects from 20 to 70 we will have an incidence of 30 subjects showing clinical signs and . We preferred to use these reports for the demonstration of the probabilistic process because in the literature the data regarding clinical signs and symptoms for Temporomandibular Disorders have too wide a variation as well as too high an incidence in our opinion.[3][4][5][6][7][8]

An example of a partition with presumed probability in which TMJ degeneration (Deg.TMJ) occurs in conjunction with Temporomandibular Disorders (TMDs) would be the following:

where
where
where
where
  • «A homogeneous partition provides what we are used to calling Differential Diagnosis.»

Clinical situations

These conditional probabilities demonstrate that each of the partition's four subclasses is causally relevant to patient data in the population sample . Given the aforementioned partition of the reference class, we have the following clinical situations:

  • Mary Poppins degeneration of the temporomandibular joint Temporomandibular Disorders
  • Mary Poppins degeneration of the temporomandibular joint no Temporomandibular Disorders
  • Mary Poppins no degeneration of the temporomandibular joint Temporomandibular Disorders
  • Mary Poppins no degeneration of the temporomandibular joint no Temporomandibular Disorders

To arrive at the final diagnosis above, we conducted a probabilistic-causal analysis of Mary Poppins' health status whose initial data were .

In general, we can refer to a logical process in which we examine the following elements:

  • an individual:
  • its initial data set
  • a population sample to which it belongs,
  • a base probability

At this point we should introduce too specialized arguments that would take the reader off the topic but that have an high epistemic importance for which we will try to extract the most described logical thread of the Analysandum/Analysans concept.

The probabilistic-causal analysis of is then a couple of the following logical forms (Analysandum / Analysans[9]):

  • Analysandum : is a logical form that contains two parameters: probability to select a person who has the symptoms and elements belonging to the set , and the generic individual who is prone to those symptoms.
  • Analysan : is a logical form that contains three parameters: the partition , the generic individual belonging to the population sample and  (Knowledge Base) which includes a set of  statements of conditioned probability.

For example, it can be concluded that the definitive diagnosis is the following:

- this means that our Mary Poppins is 95% affected by TMDs, since she has a degeneration of the Temporomandibular Joint in addition to the positive data

  1. Sarkar S, «Nagel on Reduction», in Stud Hist Philos Sci, 2015».
    PMID:26386529
    DOI:10.1016/j.shpsa.2015.05.006 
  2. DN model of scientific explanation, also known as Hempel's model, Hempel–Oppenheim model, Popper–Hempel model, or covering law model
  3. Pantoja LLQ, De Toledo IP, Pupo YM, Porporatti AL, De Luca Canto G, Zwir LF, Guerra ENS, «Prevalence of degenerative joint disease of the temporomandibular joint: a systematic review», in Clin Oral Investig, 2019».
    PMID:30311063
    DOI:10.1007/s00784-018-2664-y 
  4. De Toledo IP, Stefani FM, Porporatti AL, Mezzomo LA, Peres MA, Flores-Mir C, De Luca Canto G, «Prevalence of otologic signs and symptoms in adult patients with temporomandibular disorders: a systematic review and meta-analysis», in Clin Oral Investig, 2017».
    PMID:27511214
    DOI:10.1007/s00784-016-1926-9 
  5. Bonotto D, Penteado CA, Namba EL, Cunali PA, Rached RN, Azevedo-Alanis LR, «Prevalence of temporomandibular disorders in rugby players», in Gen Dent».
    PMID:31355769 
  6. da Silva CG, Pachêco-Pereira C, Porporatti AL, Savi MG, Peres MA, Flores-Mir C, De Luca Canto G, «Prevalence of clinical signs of intra-articular temporomandibular disorders in children and adolescents: A systematic review and meta-analysis», in Am Dent Assoc, 2016». - PMCID:26552334
    DOI:10.1016/j.adaj.2015.07.017 
  7. Gauer RL, Semidey MJ, «Diagnosis and treatment of temporomandibular disorders», in Am Fam Physician, 2015».
    PMID:25822556 
  8. Kohlmann T, «Epidemiology of orofacial pain», in Schmerz, 2002».
    PMID:12235497
    DOI:10.1007/s004820200000 
  9. Westmeyer H, «The diagnostic process as a statistical-causal analysis», in APA, 1975».
    DOI:10.1007/BF00139821
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