The Clinical Diagnostic Processes

What are the clinical diagnostic processes?

Whenever a patient consults a physician, the first thing that the latter does is to formulate a clinical diagnosis that will then serve as a steering wheel for further actions, especially treatment.  A clinical diagnosis is an initial assessment statement of the medical condition.

A clinical diagnosis is derived from processing of data gotten from interview of the patient / relatives (or what is popularly known as history) and findings obtained from the physical examination of the physician on the patient.  The data gotten from interview or history are commonly called symptoms and physical examination findings, signs.

What are the processes used in arriving to a clinical diagnosis?

One commonly hears of pattern recognition or matching complemented by prevalence as one process.  Another one is the hypothetico-deductive reasoning and abductive reasoning.  The third one is rule in rule out processes.  There could be other processes used.

What is the pattern recognition or matching complemented by prevalence process in arriving to a clinical diagnosis?

Pattern recognition or matching is the realization of the patient’s problem representation conforms to a previously learned picture or pattern of a disease.  The clinical diagnosis will be the disease that has a clinical presentation that matches that of the patient.

Prevalence process means the choice of diagnosis is based on the frequency of occurrence of the disease in a certain locality, in a certain age and sex group, and in the affected organ and system.

Here is an illustration of pattern recognition or matching complemented by the prevalence process.

Knowing the common manifestations of 5 different diseases as follows:

Disease A – abcd (manifestations)

Disease B – fghi

Disease C – klmn

Disease D – pqrs

Disease E – uvwx

Given a patient manifesting with pqrs, your diagnosis is Disease D.  The pattern recognition or matching process is being used.

Knowing the common manifestations of 3 different diseases and relative frequency of each as follows:

Disease A –  abcd (manifestations)           Least common

Disease B –  abcd

Disease C –  abcd                                              Most common

Given a patient manifesting with abcd, your diagnosis is Disease C.  The prevalence process is being used.

Pattern recognition or matching complemented by prevalence process is the one commonly used by experts and is very fast.

What is the hypothetico-deductive and abductive reasoning process in arriving to a clinical diagnosis?

In hypothetical-deductive reasoning, a physician develops hypotheses to explain a patient’s clinical problem and apply collected information to test the hypotheses in order to try and confirm or exclude a hypothesis.  The process goes: if – then – but – therefore (yes, no).    If we have certain information, then certain hypotheses may be true, but we test against further information, and therefore it is true or not.

Deductive reasoning is a basic form of valid reasoning. Deductive reasoning, or deduction, starts out with a general statement, or hypothesis, and examines the possibilities to reach a specific, logical conclusion.

Deductive reasoning goes from general to specific while inductive reasoning goes from specific to general.  It is usually the deductive reasoning that is being in clinical diagnostic process.

Abductive reasoning is a form of deductive reasoning. It usually starts with an incomplete set of observations (that is commonly seen in the practice of medicine) and proceeds to the likeliest possible explanation for the group of observations. It is based on making and testing hypotheses using the best information available. It often entails making an educated guess after observing a phenomenon for which there is no clear explanation yet.   A medical diagnosis is an application of abductive reasoning: given this set of symptoms, what is the diagnosis that would best explain most of them? While there may be no certainty about the diagnosis, since there may exist additional evidence that was not presented in the case, they make their best guess based on what they know.  (https://www.butte.edu/departments/cas/tipsheets/thinking/reasoning.html)

Illustration of a deductive and abductive reasoning in clinical practice.

Time 1 in the clinical evaluation:

A 20-year-old female presented with a concern of a neck mass.

Hypothesis 1: Thyroid or lateral neck mass, usually lymph node.

 

Time 2 in the clinical evaluation (after 1 minute):

On physical examination, there was a paratracheal mass which moves with deglutition.

Hypothesis 1.1 (refined): Thyroid mass, malignant or nonmalignant, more common is non-malignant by prevalence.

 

Time 3 in the clinical evaluation (after 5 minutes):

On further physical examination, there was a 4-cm right paratracheal mass which moves with deglutition, not fixed, not hard, with solid and cystic areas, non-tender, no erythema, no palpable cervical lymph nodes, with a pulse rate of 80 beats per minute.

Hypothesis 1.1.1 (refined): Thyroid nodule, right side, benign as there are no signals for malignancy and with characteristics suggestive of benign condition (cystic areas), most likely colloid adenomatous nodule.

 

Notice the different but refined hypotheses that were deduced from Time 1 to Time 3 based on progressively increasing and whatever data are available – an illustration of deductive and abductive reasoning in the clinical diagnostic processes.  Notice too, in the end, at Time 3, pattern recognition (matching) complemented with prevalence process was also used.  There was a pattern of benignity recognized (cystic areas) and no pattern for malignancy (palpable nodes and fixation) present.  Based on prevalence, colloid adenomatous nodule is the most common for such a clinically benign presentation.

 

What is the rule in rule out process in arriving to a clinical diagnosis?

Rule-out means to exclude the possibility of a medical condition in the diagnosis or differential diagnoses (all possible diagnosis).  Rule-in means to include the possibility of a medical condition in the diagnosis or differential diagnoses.

Rule-out (from MedicineNet.com) – “term used in medicine, meaning to eliminate or exclude something from consideration. For example, a normal chest x-ray may “rule out” pneumonia.” (http://www.medicinenet.com/script/main/art.asp?articlekey=33831)

The phrase “rule out” means that the physician is attempting to discount a particular diagnosis from the list of possible or probable conditions the patient may have. (http://www.hcpro.com/HIM-263776-5707/QA-Avoid-rule-out-language-to-ensure-medical-necessity.html)

“Rule out” is another term for differential diagnosis. The differential is a list of possible conditions that could explain the patient’s symptoms. Through continued history, exam, and lab/imaging studies, the clinician narrows the differential to come to a diagnosis. When reading “rule out” in a medical narrative, you can replace the phrase with the words “make sure it’s not.” So the phrase “chest pain, rule out myocardial infarction” can be read as “chest pain, make sure it’s not a heart attack.” (http://www.answers.com/Q/What_does_rule_out_mean_in_medical_terms)

Differential diagnosis means all the possible (usually) diagnoses that may be present in a patient.   Rule-out and rule-in are the same as considerations in a list of differential diagnoses. Ultimately, one has to decide on the most probable diagnosis to guide in the selection of a paraclinical diagnostic procedure when indicated and also treatment.

 

ROJoson’s thoughts, perceptions, opinions, and recommendations (TPORs) on the clinical diagnostic processes:

  • Whether using rule-out and rule-in or pattern recognition with prevalence processes, the hypothetico-deductive and abductive reasoning are being used.
  • Rule-out and rule-in are at best constitute a long list of differential diagnoses. Ultimately, one has to decide on the most probable diagnosis to guide in the selection of a paraclinical diagnostic procedure when indicated and also treatment.  I would recommend the use initially of hypothetico-deductive and abductive reasoning (as illustrated above) and eventually end with pattern recognition complemented with prevalence processes in formulating a clinical diagnosis.
  • Do not use “rule-out ……” in stating the clinical diagnosis of a patient. State the primary most probable clinical diagnosis with the understanding that other entities are still possible as any physician cannot be absolutely certain with a diagnosis.  Use pattern recognition (or matching) and prevalence processes in arriving to a primary clinical diagnosis. Be as specific as possible in stating the primary clinical diagnosis. If necessary for communication purposes and guide in the medical management, state also the secondary or second most probable clinical diagnosis and not a long list of possible diagnoses and diagnoses that one has to rule-out or eliminate.
  • Limiting to at most 2 differential diagnoses is the more cost-effective clinical diagnostic process as it zeroes in on the two most probable rather than considering all the possibilities (remember in medicine, anything is possible). When a paraclinical diagnostic procedure has to be done, it is guided by the two most probable diagnoses, oftentimes, the primary one.  The primary objective of the paraclinical diagnostic procedure is to firm up the certainty on the primary or most probable diagnosis.  If one goes by a long list of differential diagnoses which consist of all possible diagnoses to rule-in and rule-out, a shot-gun request for paraclinical diagnostic procedures usually ensues.
  • Limiting to at most 2 differential diagnoses does not mean one excludes all the other possible diagnoses. They are just down in the unwritten list of possibilities which the physician is constantly cognizant of. The primary clinical diagnosis is the working diagnosis and after its formulation, it should guide the physician on what to do next in the continuing management of the patient.
  • Using the pattern recognition (matching) complemented by prevalence processes together with deductive and abductive reasoning is more efficient (including cost-wise) compared to rule-out and rule-in processes in actual patient management.
  • Rule-out diagnoses are not acceptable as primary diagnoses on PhilHealth and other health insurance claims.

ROJ-TPOR@16jan25

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