C H A P T E R 1

Clinical reasoning, evidence­based practice, and symptom analysis Basic health assessment involves the application of the practitioner’s knowledge and skills to identify and distinguish normal from abnormal findings. Basic assessment often moves from a general survey of a body system to specific observations or tests of function. Such an approach to assessment and clinical decision making uses a deductive process of reasoning. For example, a specialist examining a patient with known hyperthyroidism would conduct a physical examination to test for deep tendon reflexes. Brisk or hyperreflexic reflexes would lead the practitioner to conclude that a hyperthyroid state is a likely cause of these findings. This would greatly narrow the choices of diagnostic tests and treatment decisions.

Advanced assessment builds on basic health assessment yet is performed more often using an inductive or inferential process, that is, moving from a specific physical finding or patient concern to a more general diagnosis or possible diagnoses based on history, physical findings, and the results of laboratory and diagnostic tests. The practitioner gathers further evidence and analyzes this evidence to arrive at a hypothesis that will lead to a further narrowing of possibilities. This is known as the process of diagnostic reasoning.

Diagnostic reasoning Diagnostic reasoning is a scientific process in which the practitioner suspects the cause of a patient’s symptoms and signs based on previous knowledge. The practitioner gathers relevant information, selects necessary tests, makes an accurate diagnosis, and recommends therapy. The difference between an average and an excellent practitioner is the speed and focus used to arrive at the correct conclusion and initiate the best course of evidence­based treatment with minimum harm, cost, inconvenience, and delay. This expertise of the practitioner is acquired through knowledge and a skill set developed through experience in clinical practice. Repeated practice with real cases helps to develop memory schemes for relating clinical problems and store them in long­term memory.

By using diagnostic reasoning, the practitioner is able to accomplish the following:

• Determines and focuses on what needs to be asked, what data need to be obtained, and what needs to be examined

• Performs examinations and diagnostic tests accurately • Clusters all pertinent findings • Analyzes and interprets the findings • Develops a list of likely or differential diagnoses

The diagnostic process

The primary care context The process of assessment in the primary care setting begins with the patient or caregiver stating a reason for the visit or a chief concern. Most visits to primary care providers involve concerns or symptoms presented by the patient, such as an earache, vomiting, or fatigue. The initial evidence is collected through a patient history. Demographic information, such as gender, age, occupation, and place of residence, is obtained to place the patient in a risk category that may rule out certain diagnoses immediately. In most primary care settings, routine vital signs are obtained, which can include height and weight, temperature, pulse, respiratory rate,

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blood pressure, last menstrual period, and smoking status. While obtaining the history, the practitioner also makes observations of the patient’s appearance, interaction with family members, orientation, and mental and physical condition. The practitioner notes any unusual presentations that could help focus the assessment process.

Symptom analysis Presenting symptoms need to be explored with further questions. One useful mnemonic for gathering this information is COLDSPA.

Character: How does it feel, look, smell, sound? Onset: When did it start? Location: Be specific. Where is it? Does it radiate? Duration: How long does it last? Does it recur? Severity: How do you rate your pain on a scale from 0 (no pain) to 10 (worst pain I’ve ever had)? Pattern: What makes it better? What makes it worse? What have you done and did it help? Associated factors: What other symptoms do you have? How much does it interfere with your usual

activities?

Another mnemonic is OLDCARTS: onset, location, duration, character, aggravating or associated factors, relieving factors, temporal factors, and severity.

Information can also be gleaned from the review of systems. A final step is to ask about the patient’s or caregiver’s perception of the meaning of the symptom(s). The practitioner then clusters the information into logical groups based on prior knowledge of symptom clusters associated with specific diagnoses or body systems. At the conclusion, the history of the presenting concerns should give the practitioner a good idea of the most likely differential diagnoses. These hypotheses may be further strengthened during the physical examination.

Performing a physical examination This section may be performed as a complete physical examination or as a focused or localized examination that emphasizes the body or organ systems most likely affected by the patient’s presenting symptoms.

Formulating and testing a hypothesis The practitioner then formulates a hypothesis based on expertise and knowledge of possible pathological, physiological, or psychological processes. Further interpretation of evidence refines the hypothesis to a working or probable diagnosis. Hypothesis generation begins during the assessment of the patient’s age, gender, race, appearance, and presenting problem. Age is often the most significant variable in narrowing the probabilities of a problem. Hypothesis generation forms the context in which further data are collected. This context includes the setting in which care is delivered, such as in a hospital, in an outpatient setting, or in another community­ based setting where more than a single individual could be affected. Clinical decision making can be filled with uncertainty and ambiguity. Because available evidence is almost never complete, hypothesis formation involves some element of subjective judgment.

The hypothesis must then be tested and assessed for the following characteristics.

• Coherence: Are the physiological links, predisposing factors, and complications for this disease present in the patient?

• Adequacy: Does the suspected disease encompass all of the patient’s normal and abnormal findings? • Parsimony: Is it the simplest explanation of the patient’s findings? The surest way to make this

determination is to ask the patient or the caregiver the reason for seeking care and the current understanding of the problem and possible treatment options. This is a crucial step because patients must find the treatment recommendation acceptable.

• Diagnostic probability: Is the diagnosis confirmed by radiographic or laboratory tests? A rational diagnostic hypothesis is one that, if confirmed by the select tests, limits the need for additional confirmation.

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• Eliminate a competing hypothesis: What other diseases could explain the patient’s symptoms?

To confirm the hypothesis, the practitioner establishes a “most likely” diagnosis as a basis for a treatment plan and evaluates the outcome. The goal of a clinical decision is to

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choose an action that is most likely to result in the health outcomes the patient desires. This step of the decision­making process involves personal preference as to whether the benefits outweigh the harms involved, whether the cost is reasonable, and whether the most desired outcomes are short or long term.

Practitioners make extensive use of heuristics, or rules of thumb, to guide the inductive or inferential process of diagnostic reasoning. Heuristics are generally accurate and useful rules to make the task of information gathering more manageable and efficient—rules such as familiarity, salience, and resemblance to a patient who has a known disease. On occasion, however, heuristics can be faulty, particularly if the presentation is atypical or the condition is rare. The practitioner must always be open to a low probability of a serious diagnosis. Heuristics can have negative effects when stereotypes or biases influence judgment. For example, assuming that a patient is heterosexual can lead to errors in clinical reasoning and differential diagnosis when evaluating the symptom of rectal pain.

Expert versus novice practitioners Students of advanced assessment have a variety of backgrounds, with many coming from specialized areas of clinical practice. Such students could have difficulty broadening the scope of their observations and clinical possibilities. In any case, nonexperts tend to be nonselective in data gathering and in the clinical reasoning strategies they use. Experts, however, are able to focus on a problem, recognize patterns, and gather only relevant data, with a high probability of a correct diagnosis. The goal for a novice practitioner is to aim for competence and expertise.

A competent practitioner will execute the following steps:

1. Identify the most important cues. These cues are obtained largely through thorough symptom analysis (e.g., COLSDPA or OLDCARTS), functional assessment, and history to assess the patient’s beliefs and understanding or explanatory model of the illness. Research evidence shows that a person’s beliefs or explanatory models of an illness or a symptom include a cause, an opinion about the timeline (acute or chronic), consequences of the condition (minor or life threatening), and some type of verbal label used to identify the cluster of symptoms or sensations (e.g., “the flu,” “the blues”). Practitioners need to distinguish between the presence of disease, which has a biological basis, and illness, which is the human experience of being sick that could have little correlation with the objective evidence available.

2. Understand and perform advanced examination techniques. These techniques can include special maneuvers and closer observation of fine details during the physical examination, more in­depth interviews using valid and reliable instruments to assess the patient’s risk for a specific diagnosis, and “gold standard” diagnostic tests for the identification of a specific disorder.

3. Test differential or competing diagnoses. A differential diagnosis results from a synthesis of subjective and objective findings, including laboratory and diagnostic tests, with knowledge of known and recognized patterns of signs and symptoms. When using the “rule­out” strategy, the practitioner looks for the absence of findings that are frequently seen with a specific condition; the absence of a sensitive finding is strong evidence against the condition being present. When using the “rule­in” strategy, the practitioner looks for the presence of a finding with high specificity (low false­positive and high true­negative values); the presence of this finding is strong evidence that the condition is present.

4. See a pattern in the information gathered. A pattern or cluster of findings can emerge from the subjective and objective data. This pattern could be evident during one patient encounter, or it could depend on a pattern of signs and symptoms that develops over time. Often an expert practitioner can eliminate competing diagnoses only after the initial treatment prescribed is ineffective or after the symptoms either disappear sooner than expected or persist longer than expected.

Developing clinical reasoning Clinical reasoning is a situational, practice­based form of reasoning that acknowledges the many variables that are present in an actual clinical situation, such as environmental and social factors involving the patient, family, community, and a team of health care providers. Clinical reasoning involves developing a brief summary in which patient­specific details are translated into appropriate diagnostic terminology. This process requires a

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background of scientific and evidence­based knowledge about general cases and a practical ability to evaluate the relevance of the evidence behind general scientific and technical knowledge and how it applies to a particular patient. In doing so, the clinician considers the patient’s particular clinical trajectory; her or his concerns, values and preferences; and her or his particular vulnerabilities (e.g., having multiple comorbidities) and sensitivities to care interventions (e.g., known drug allergies and past responses to therapies) when formulating clinical decisions or conclusions.

Negotiating goals and expectations of a patient encounter It is important, especially in an ambulatory care setting, to identify the patient’s goals, expectations, and resources to determine what needs to be achieved during an encounter. A patient who seeks care because of a bothersome symptom could be more interested in having the symptom relieved by a particular date than in knowing the cause or diagnostic explanation for the symptom. Other patients might want reassurance that a symptom or sign is not a serious condition and yet do not expect treatment to alleviate the sensations they are experiencing. An explicit discussion between the practitioner and patient is necessary