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Arriving at a Medical DiagnosisArriving at a Medical DiagnosisDr. Gary MumaughDr. Gary Mumaugh

Disease Names - Essential Diagnostic LabelsDisease Names - Essential Diagnostic Labels For thousands of years, physicians have recorded observations and studies about For thousands of years, physicians have recorded observations and studies about

their patients.their patients. In accumulating these facts, they have recognized patterns of pathological structureIn accumulating these facts, they have recognized patterns of pathological structure

and function.and function. When these categories were distinctive, they were termed diseases and given When these categories were distinctive, they were termed diseases and given

specific names.specific names.

Two Meanings of “Diagnosis”Two Meanings of “Diagnosis” The name of the patient’s disease or state of altered function is termed “diagnosis” The name of the patient’s disease or state of altered function is termed “diagnosis”

or “a diagnosis”or “a diagnosis”o In this instance, diagnosis is a name

The act of searching for or determining the patient’s disease is commonly referred toThe act of searching for or determining the patient’s disease is commonly referred to as “a diagnosis” or “the making of a diagnosis”as “a diagnosis” or “the making of a diagnosis”

o In this instance, diagnosis is a process The word diagnostician is rarely usedThe word diagnostician is rarely used

The Diagnostic “Four Step”The Diagnostic “Four Step” Step 1 – Acquisition of FactsStep 1 – Acquisition of Facts Step 2 – Evaluation of FactsStep 2 – Evaluation of Facts Step 3 – Listing of HypothesesStep 3 – Listing of Hypotheses Step 4 – Choosing Between Hypothesis – also known as Differential Diagnosis (DD)Step 4 – Choosing Between Hypothesis – also known as Differential Diagnosis (DD)

Step 1 – Acquisition of FactsStep 1 – Acquisition of Facts The medical history gives a chronology of the symptomsThe medical history gives a chronology of the symptoms Symptoms are subjectiveSymptoms are subjective

oo They are reported by the patientThey are reported by the patient The physical examination discloses physical signsThe physical examination discloses physical signs

oo Physical signs are objectivePhysical signs are objective

Step 2 – Evaluation of FactsStep 2 – Evaluation of Facts As new facts are acquired, you will repeatedly tests these facts for accuracy, As new facts are acquired, you will repeatedly tests these facts for accuracy,

reliability, and relevance to the patient’s problem.reliability, and relevance to the patient’s problem. You must judge if the facts have been colored by the patient’s emotions.You must judge if the facts have been colored by the patient’s emotions. You must question the motives that may lead to distortion.You must question the motives that may lead to distortion. You must conclude if the items are relevant or trivial to the identification of the You must conclude if the items are relevant or trivial to the identification of the

patient’s disease.patient’s disease.

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Step 3 – Listing of HypothesisStep 3 – Listing of Hypothesis The provider accumulates a list of diseases suggested by the diagnostic clues taken The provider accumulates a list of diseases suggested by the diagnostic clues taken

from the history, the physical examination and the laboratory and other testsfrom the history, the physical examination and the laboratory and other testso Disease 1 has clues a, b, c, do Disease 2 has clues b, c, f, go Disease 3 has clues a, d, go Disease 4 has clues b, c, g, h

To be a useful clinician, the information must be reorganized in the following manner:To be a useful clinician, the information must be reorganized in the following manner:oo clue a suggests disease 1, 3clue a suggests disease 1, 3oo clue b suggests disease 2clue b suggests disease 2oo clue c suggests disease 2clue c suggests disease 2oo clue d suggests disease 1, 2, 3, 4clue d suggests disease 1, 2, 3, 4oo clue e suggest disease 2, 3clue e suggest disease 2, 3oo Etc.Etc.

This means that the clinician must devise and memorize lists of diseases with This means that the clinician must devise and memorize lists of diseases with common manifestations that are key signs or key symptoms.common manifestations that are key signs or key symptoms.

oo Examples of lists:Examples of lists: Causes of dyspnea are… Causes of fever are… Causes of joint pain are… Etc.

In the four-step sequence of diagnosis, the lists of hypotheses are derived from the In the four-step sequence of diagnosis, the lists of hypotheses are derived from the diseases called to mind by their key signs and symptoms.diseases called to mind by their key signs and symptoms.

Step 4 - Choosing Between HypothesesStep 4 - Choosing Between Hypotheses Each disease in the list of hypotheses is considered in turn and it’s manifestations Each disease in the list of hypotheses is considered in turn and it’s manifestations

are matched with the patientsare matched with the patients Initial comparisons may eliminate some items from the list and retain othersInitial comparisons may eliminate some items from the list and retain others The chronology of patient’s signs and symptoms is compared with that of the The chronology of patient’s signs and symptoms is compared with that of the

suspected diseasesuspected disease Some diseases will be excluded by the durationSome diseases will be excluded by the duration

o Example – a five year cough would not be attributed to lung cancer, since this diagnosis is fatal in one year

From the list that survives the testing, one chooses as From the list that survives the testing, one chooses as the diagnosis the diagnosis the disease the disease whose attributes coincide more closely with the patientswhose attributes coincide more closely with the patients

If a good fit is not found, the clinician resumes the search for more signs and If a good fit is not found, the clinician resumes the search for more signs and symptomssymptoms

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In selecting the diagnosis from the list of the hypotheses, start first with one single In selecting the diagnosis from the list of the hypotheses, start first with one single disease to explain all the patient’s manifestations rather than explain them by the disease to explain all the patient’s manifestations rather than explain them by the coincidence of several diseasescoincidence of several diseases

o This is called the law of parsimony For example, if a patient has dilated heart, hepatomegaly, ascites and

pedal edema, the single likely diagnosis would be cardiac failure – which is more likely than heart disease producing enlargement and cirrhosis with hepatomegaly