Case Based Reasoning (CBR) Adaptation Problem and its

Solution in Treating Hypothyroidism

Abel M. Gebreyesus abel@cs.dal.ca

ABSTRACT:

The widely used definition of Case Based Reasoning (CBR) is similar cases of a certain

problem has related solutions. Likewise, it is widely assumed that similar differences

among case descriptions imply similar differences among their solutions. In this case,

CBR looks to be a best solution to many unresolved medical questions and medical

knowledge based systems, like in the case of hypothyroidism treatment. The main

challenge, however, in finding the best solution in treating hypothyroidism with the exact

dosage of levothyroxine therapy is each case is unique and difficult to derive conclusions

from the previous cases (reasons). Some researches imply that case based reasoning

through adaptation has a challenge in treating hypothyroidism. Nevertheless, CBR would

be successful if the adaptation issue is solved. Adaptation is one of the most problematic

steps in the design and development of case-based reasoning (CBR) systems. Recently,

some researches have been done and scientific discussions are emerging to solve the

adaptation issue. So, in this paper, I would discuss the role of adaptation in the design and

development of case-based reasoning in treating hypothyroidism as well as assess the

recently emerged CBR adaptation techniques and their implication to the hypothyroid

treatment.

KEYWORDS Case-Based Reasoning (CBR), Adaptation, Hypothyroidism, Case Structure, levothyroxine therapy

1. INTRODUCTION TO HYPOHYROIDISM

Hypothyroidism refers to any state that results in a deficiency of thyroid hormone, including

hypothalamic or pituitary disease and generalized tissue resistance to thyroid hormone, and disorders

that

affect the thyroid gland directly. The clinical manifestations of hypothyroidism emerge insidiously, are

nonspecific, and often are attributed to aging. They include a general slowing down, mental depression,

modest weight gain, intolerance of cold, constipation, vague aches and pains, dryness

of the skin, and

brittleness of the scalp hair. [1]

1. 1 Differential Diagnosis

Figure 1. Differential Diagnosis for hypothyroidism [2]

Hypothyroidism is the clinical syndrome resulting from deficient thyroid hormone action. Overt

hypothyroidism is found in 2% of women aged more than 70 years and in 0.5% of women aged 40 to 60

years. Hypothyroidism is present in 0.8% of men older than 60 years and is rare in women younger than

40 years and men younger than 60 years. [3]

In primary hypothyroidism, the thyroid-stimulating hormone (TSH) level is elevated, and free

thyroid hormone levels are depressed. In secondary hypothyroidism, the TSH level is low or undetectable.

A follow-up assessment of the free thyroxine level can help distinguish between primary and secondary

hypothyroidism.[4]

The evaluation of patients with new-onset hypothyroidism is quite limited. In patients with

primary hypothyroidism, the thyroid stimulating hormone (TSH) level is elevated, indicating that thyroid

hormone production is insufficient to meet metabolic demands, and free thyroid hormone levels are

depressed.[4]

In contrast, patients with secondary hypothyroidism have a low or undetectable TSH level. TSH

results have to be interpreted in light of the patient‟s clinical condition. A low TSH level should not be

misinterpreted as hyperthyroidism in the patient with clinical manifestations of hypothyroidism. When

symptoms are nonspecific, a follow-up assessment of the free thyroxine (T4) level can help distinguish

between primary and secondary hypothyroidism. [4]

Causes of Hypothyroidism Common Signs and Symptoms

of Hypothyroidism

Primary hypothyroidism (95% of cases)

Idiopathic hypothyroidism*

Hashimoto‟s thyroiditis

Irradiation of the thyroid subsequent

to Graves‟

disease

Surgical removal of the thyroid

Late-stage invasive fibrous

thyroiditis

Iodine deficiency

Drug therapy (e.g., lithium,

interferon)

Infiltrative diseases (e.g.,

sarcoidosis, amyloidosis,

scleroderma, hemochromatosis)

Secondary hypothyroidism (5% of cases)

Pituitary or hypothalamic neoplasms

Congenital hypopituitarism

Pituitary necrosis (Sheehan‟s

syndrome)

Sign or symptom Affected patients (%)

Weakness 99

Skin changes 97

(dry or coarse skin)

Lethargy 91

Slow speech 91

Eyelid edema 90

Cold sensation 89

Decreased sweating 89

Cold skin 83

Thick tongue 82

Facial edema 79

Coarse hair 76

Skin pallor 67

Forgetfulness 66

Constipation 61

Table 1. Causes as well as signs and symptoms of hypothyroidism

Source: Rosenfeld JA, Alley N, Acheson LS, Admire JB, eds. Women’s health in primary care. Baltimore: Williams & Wilkins, 1997:617-31

Once the diagnosis of primary hypothyroidism is made, additional imaging or serologic testing is

unnecessary if the thyroid gland is normal on examination. In patients with secondary hypothyroidism,

further investigation with provocative testing of the pituitary gland can be performed to determine if the

underlying cause is a hypothalamic or pituitary disorder. In patients with pituitary dysfunction, imaging is

indicated to detect microadenomas, and levels of other hormones that depend on pituitary stimulation

should also be measured. In general, evidence of decreased production of more than one pituitary

hormone is indicative of panhypopituitary problems. [4]

1. 2 Hypothyroidism and depression

One of the common characteristics of hypothyroidism is depression. Depression in

hypothyroidism and the cause for many disorders as well as an effect many disorders. Due to the change

of metabolic hormone, food is not easily metabolized. As a result, since blood is not getting enough

oxygen, feeling of dizziness is the main sign for hypothyroid patients. Generally, hypothyroidism and

depression have in common.

So, this depression, which caused by hypothyroidism can treated by:

Choice of medication

Adjustment of therapy

Follow-up care

2. CASE-BASED REASONING SYSTEMS

CBR is a problem-solving method that stores the past solved problems and remembers them when

solving future problems. A case represents knowledge at an operational level and comprises of problem

description, associated solution to resolve the problem and the possible outcome of the solution. [4]

It is a reasoning technology that uses specific knowledge from the past cases to interpret new case

or to determine solution to a new problem. Various synonyms are used for CBR like instance-based,

exemplary-based, memory-based and analogy-based reasoning.

Case-Based Reasoning (CBR), a form of problem solving in which the problem solver

reuses a past case to solve a new problem. CBR is both a model of human cognition and a

paradigm for computer- based problem solvers. CBR is a process of “remember and compare” or “remember and adapt” The two types of CBR

are Interpretive CBR in which the past cases are interpreted and justified on the new solution and

Problem Solving CBR in which the retrieved past solution is altered to suit the new case.[5]

Figure 2. Classical case-based reasoning cycle[6]

CBR fulfils two main tasks: the first is the retrieval, which means to search for or to

calculate the most similar cases. The second task, the adaptation (reuse and revision), means a

modification of solutions of former similar cases to fit for a current one. If there are no important

differences between a current and a similar case, a simple solution transfer is sufficient.

Sometimes only few substitutions are required, but in other situations the adaptation is a very

complicated process. So far, no general adaptation methods or algorithms have been developed.

The adaptation is still absolutely domain dependent. [7] Case-based reasoning is a problem solving paradigm that in many respects is fundamentally

different from other major AI approaches. Instead of relying solely on general knowledge of a problem

domain, or making associations along generalized relationships between problem descriptors and

conclusions, CBR is able to utilize the specific knowledge of previously experienced, concrete problem

[Type text]

situations (cases). A new problem is solved by finding a similar past case, and reusing it in the new

problem situation. A second important difference is that CBR also is an approach to incremental,

sustained learning, since a new experience is retained each time a problem has been solved, making it

immediately available for future problems. The CBR field has grown rapidly over the last few years, as

seen by its increased share of papers at major conferences, available commercial tools, and successful

applications in daily use.[8]

2.1 Case Retrieval

This first step comprises of description of the patient problem where a detailed patient history

(that includes the signs and symptoms) has been recorded. When a user inputs this new case, the „closer

match‟ past cases which contain similar possible symptoms and the conclusions drawn from them are

retrieved from the case library as a reference to solve the new problem.[9]

2.2 Case reuse, Adaptation

When the reference cases show a strong similarity with the new case, the respective diagnosis is

reused as a solution for the current case and if the recommended solution obtained from the previous

similar cases has to be altered to match the current problem then an adaptation technique is used. In this

instance there is either a transformed new case solution or a derived new case solution. One such case

adaptation strategy is the compositional adaptation technique where the broad base of medical

information is adapted to individual personalized content.[10]

2.3 Case Revision, Verification

Once an appropriate solution to the current case has been obtained then the case is evaluated to

confirm the accuracy of the proposed new solution. If the generated case solution is successful then it‟s

used as an important reference case for future application and if unsuccessful then the case solution is

repaired by identifying the potential problems. [5]

2.4. Case Repartition

When the retrieved case description is an exact match as the new case description then the same

solution is used and this new case is not stored in the case base .If there are better solutions than the

retrieved past solution to solve the new problem, then a repartition of world of solutions and world of

problems takes place . The current case either has a new partition in the case base or based on the

similarity relations the new problem is included to the partition of the past problems, so it‟s a form of

partition based reasoning. [5]

2.5 Case Retention and Learning

The useful experience gained by solving the current case is retained to solve future problems and

the outdated cases are erased or modified in the case base to increase the accuracy of cases. [5]

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3. ADAPTATION IN MEDICINE: THE BOTTLENECK OF CBR

According to the assumption of adaptation theory in CBR, similar problems have similar

solutions. Thus, the effort required to adapt a retrieved solution will be less the more similar it is to the

required solution.

In medicine, CBR has mainly been applied for diagnostic and partly for therapeutic tasks. Cased-

Based Reasoning seems to be a suitable technique for medical knowledge based systems. However, the

adaptation task is the bottleneck that has to be solved.

Still, different researchers described their reservation about the limitation of adaptation. Macura

et al, for instance said: “to use Cased-Based Reasoning a few problems have to be solved: a representation

form for cases has to be determined, and an appropriate retrieval algorithm has to be selected. Moreover,

an infinite growth of the case base should be avoided e.g. by clustering cases into prototypes and

removing redundant ones, or by restricting the case base to a fixed number of cases and updating it during

expert consultation sessions[11]. However, according to Bergmann and Wilke, “the main problem of the

CBR method is the adaptation task. Little research has been undertaken on this topic and only formal

adaptation models” [12], but no general methods have been developed so far. As Gierl and

Stengel_Rutkowski clearly elaborated, the adaptation still depends on domain and application

characteristics. “Sometimes no adaptation is necessary, because e.g. the field and the cases are as

unspecialised as in FLORENCE. Sometimes the adaptation is a simple solution transfer or only a little bit

more, sometimes just a few constraints have to be checked”, [13] they noted. As Schmidt et al

underlined, adaptation is not only a problem for medical applications. However, in medicine it increases,

because cases often consist of an extremely large number of features. In non-medical CBR applications,

the adaptation is usually solved by a set of specific adaptation rules, which usually have to be acquired

during expert consultation sessions. As these rule sets have to consider all possible important differences

between current and former similar cases, for medical applications it is mostly impossible to generate

such sets. So, some adaptation solutions have been developed that are not limited to, but are rather typical

for medical domains.[7]

4. THE PROBLEM OF ADAPTATION IN MEDICINE

Many researchers are working on medical CBR with many diverse applicationsranging

from psychiatry and epidemiology to clinical diagnosisMost of them aim for a successful

implementation of CBR methods to enhance the work of health experts to improve the efficiency

and quality of health care [14]

A number of techniques are emerging from the adaptation research areas in different

sectors, like in auto factories, pharmaceutical companies and others. However, in medicine it is

not yet successful, mainly it deals with perfection. Since it deals with human beings, any

adaptation technique should be perfect or near to perfect, which is one of the main challenges of

adaptation in medicine.

4.1 Adaptation Problem in Hypothyroidism

However, the only treatment at present, levothyroxine therapy has a number of problems

associated with it. Due to these problems, hypothyroid patients need continuous treatment and follow-up.

Some of the problems:

[Type text]

Actual content of thyroid hormone varies considerably from manufacturer to

manufacturer and even within product.

Patients switched from one product to another showed insignificance variations in

thyroid function

Life long Treatment – Needs to be monitored continuously for better treatment results

Thus, we need to solve this treatment problem

Figure 2. The cycle of hypothyroidism treatment in a CBR cycle

5 ADAPTATION TECHNIQUES FOR HYPOTHYROIDISM

Depending on the type of the patients, hypothyroid patients treated with different doses of

levothyroxine therapy. In our case, in order to give better treatment with successful adaptation

technique, different techniques can be used. In this specific case of hypothyroidism treatment by

adaptation technique, Schmidt et al, are the leaders. According to them, there can be done four kinds

of techniques. Although they suggest those four techniques, still there is no complete solution to the

adaptation problem.

7.1 Abstraction and Hypothyroidism

Such CBR system decomposes a complex problem into a hierarchy of several levels of

abstraction. These abstraction levels can be stored as abstract cases or stored in a single case Abstract

cases can be helpful as case indices and can also be helpful to define the semantics of similarity. A case is

preferred over a less concrete one because the more concrete the case is, the more details it has, and thus

easier to apply its solution for the problem of the query case because less solution refinement is

needed.[15]

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7.2 Compositional Adaptation and Hypothyroidism

In compositional adaptation, solutions from multiple cases are combined to produce a new

composite solution.[16] For instance, in in TA3-IVF [22], a system to modify in vitro fertilisation

treatment plans, relevant similar cases are retrieved (the relevance has to be specified by the user) and

Compositional Adaptation computes weighted averages for the solution attributes. The weights per

retrieved case are determined by the similarity to the current patient; the values of the solution attributes

are nominal valued.[17]

According to Arshadi and Badie research in adaptation results, they developed a system solves

new problems first the user request (including keyword, searching area, the current knowledge level of

the user and the desired status of knowledge) is presented to the system as the input information. The

system then retrieves the most similar cases from the case library, and tries to adapt the corresponding

solutions such that it could best fit the ongoing situation.[18]

There are three types of compositional adaptation:

Substitution

Compensation

Calculation

7.3 Constraints and Hypothyroidism

A more successful technique is the application of constraints. The technique is just a reduction of

a list of solutions (therapies) by constraints (contraindications). The provided list of prototypes is checked

by a set of explicit constraints. These constraints state that some features of the patient either contradict or

support specific prototypes (diagnoses). So the provided list of prototypes is reduced by contradictions

and sorted anew because of evidences. [18]

7.4 Adaptation Rules and Operators

Adaptation rules and operators is not successful technique, according to CBR analysts. One of the

reason is, “the development of complete adaptation rule bases never became a successful technique to

solve the adaptation problem in medical CBR systems, because the bottleneck for rule-based medical

expert systems, the knowledge acquisition, not only occurs again, but also seems to be more difficult to

overcome.”[17]

8. REPRESENTATION ISSUE IN HYPOTHYRODISM TREATMENT

In adaptation technique for the hypothyroidism treatment, as in any cases, there is a challenge,

though there are a number of researches are gong on. The case representation process is one of the main

steps on the Case Base construction where each decision could condition the rest of the system, but also

each technique used could affect on the final design of the case.[19]

The basic retrieval algorithms for indexing, Nearest Neighbor match, pre-classification, etc. have

already been developed some years ago and have been improved in the recent years.

Different researchers use different adaptation representation techniques. Different forms of

adaptation exist, such as null adaptation, transformational adaptation (including substitutional and

structural adaptation), and generative adaptation.

For instance, Juarez et al use structural adaptation. According to them, “It supports the

reorganization of solution elements and permits the addition and deletion of such elements under certain

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conditions. Also, structural adaptation systems use a fixed set of adaptation operators and/or

transformation rules that modify the structure of the solution depending on the relation between the

description of the query and the similar case PERSO develops a solution to a novel case by choosing the

most similar case and applying a set of rules.”[19]

Lorcan Coyle, Conor Hayes, Pádraig Cunningham, in their research developed a CBML tool.

Using a standard XML-based metalanguage, CBML, is a key to enabling CBR applications to integrate

with existing information systems. Using XML affords many advantages such as ease of transformation,

flexibility of presentation and potential to create hybrid systems easily. The maturity of the XML schema

definition has allowed us to develop CBML so that it can handle complex hierarchical case structures as

well as the commonly used flat vector format.[20]

However, the above tool is mainly used for travelers; and it is personalized. It would be difficult

to incorporate for medical purposes. Although the initiative is very productive for travelers, it would be

difficult to use it for treatment purposes. May be that is why there are not many researches in the

adaptation circle in relation to treatment or in general in medical problem solving areas.

9. DISCUSSION

There are two different tasks of determining an appropriate dose. The first one aims to determine

the initial dose, while later on the dose has to be updated continuously during a patient's lifetime. Precise

determination of the initial dose is most important for newborn babies with congenital hypothyroidism,

because for them every week of proper therapy counts.[17]

Knowledge in health related domains is complex and constantly evolving as the knowledge is

incomplete. The practice in these domains also involves substantial amount of subjective knowledge and

personal experience of the practitioners. [21]

Adaptation remains a problem in CBR in medicine and only a few systems are used in a clinical

setting. As in other domainscase mining is becoming an important area of researchThere are some

exciting future areas such as Web-based electronic medical recordsthe concept of well patient care

records having access to and monitoring your health even if you are wellpersonalization handheld

computing for clinical decision support in hospitals and the nexus of CBR and evidence-based

practicewhich all argue well for using CBR in medicine [14]

10. CONCLUSION

Generally, case based reasoning is one of suitable topics for medical problem solution. Since

many researches were done in the area, it becomes one of well developed research areas. The basic

concept of case based reasoning is also matches with the very concept of medicine and treatment.

Starting from ancient times, when healers or physicians diagnose, prescribe drugs or lab test and deal

with different therapy, they use their natural case based reasoning. So, the essence of case based

reasoning correspondence with the essence of medicine.

However, as case based reasoning is introduced in computer applications, the adaptation

issue becomes a bottle neck. As much as possible, since solutions should be perfect to the problem.

In medicine, since the problem solving activity is dealing with human beings, the solutions should be

perfect or near to perfect.

There are some researches done to challenge such problem in treating hypothyroidism; but

still it is a long way to go. As a family of endocrine disease, the challenge to hypothyroidism is a

challenge to most endocrine therapy. So, the solution for hypothyroidism could be a solution of

endocrine therapy, as well as a big step for medical problems. As hypothyroidism is a common

disorder among Canadians and most common to old females, trying to solve a problem means trying

to help one in 50 age 60 or over or one in 150 age 20 or over, in a Canadian figure.

[Type text]

In any scientific research, challenge means opportunity, as long as there is nothing

impossible to human knowledge. So, if one takes the adaptation problem, in this case hypothyroidism

treatment, a challenge means an opportunity to be solved by dedicated researches.

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