• Part 1 Approach to the Patient

• Part 2 Approach to Clinical Problem-Solving

• Part 3 Approach to Reading

Part 1. Approach to the Patient

The transition from the textbook or journal article to the clinical situation is one of the most challenging tasks in medicine. Retention of information is difficult; organization of the facts and recall of myriad data in precise application to the patient are crucial. The purpose of this text is to facilitate in this process. The first step is gathering information, also known as establishing the database. This includes taking the history (asking questions), performing the physical examination, and obtaining selective laboratory and/or imaging tests. Of these, the historical examination is the most important and useful. Sensitivity and respect should always be exercised during the interview of patients.

HISTORY

1. Basic information: Age, gender, and ethnicity must be recorded because some conditions are more common at certain ages; for instance, pain on defecation and rectal bleeding in a 20-year-old may indicate inflammatory bowel disease, whereas the same symptoms in a 60-year-old would more likely suggest colon cancer.

2. Chief complaint: What is it that brought the patient into the hospital or clinic? Is it a scheduled appointment or an unexpected symptom? The patient’s own words should be used if possible, such as, “I feel like a ton of bricks are on my chest.” The chief complaint, or reason for seeking medical attention, may not be the first subject the patient talks about (in fact, it may be the last thing), particularly if the subject is embarrassing, such as a sexually transmitted disease, or highly emotional, such as depression. It is often useful to clarify exactly what the patient’s concern is; for example, the patient may fear the headaches represent an underlying brain tumor.

3. History of present illness: This is the most crucial part of the entire database. The questions one asks are guided by the differential diagnosis one begins to consider the moment the patient identifies the chief complaint, as well as the clinician’s knowledge of typical disease patterns and their natural history. The duration and character of the primary complaint, associated symptoms, and exacerbating/relieving factors should be recorded. Sometimes, the history will be convoluted and lengthy, with multiple diagnostic or therapeutic interventions at different locations. For patients with chronic illnesses, obtaining prior medical records is invaluable. For example, when extensive evaluation of a complicated medical problem has been done elsewhere, it is usually better to first obtain those results than to repeat a “million-dollar workup.” When reviewing prior records, it is often useful to review the primary data (eg, biopsy reports, echocardiograms, serologic evaluations) rather than to rely upon a diagnostic label applied by someone else, which then gets replicated in medical records and, by repetition, acquires the aura of truth, when it may not be fully supported by data. Some patients will be poor historians because of dementia, confusion, or language barriers; recognition of these situations and querying of family members are useful. When little or no history is available to guide a focused investigation, more extensive objective studies are often necessary to exclude potentially serious diagnoses.

4. Past history:

   1. Illness: Any illnesses such as hypertension, hepatitis, diabetes mellitus, cancer, heart disease, pulmonary disease, and thyroid disease should be elicited. If an existing or prior diagnosis is not obvious, it is useful to ask exactly how it was diagnosed, that is, what investigations were performed. Duration, severity, and therapies should be queried.

   2. Hospitalization: Any hospitalizations and emergency room visits should be listed with the reason(s) for admission, the intervention, and the location of the hospital.

   3. Blood transfusion: Transfusions with any blood products should be listed, including any adverse reactions.

   4. Surgeries: The year and type of surgery should be elucidated and any complications documented. The type of incision and any untoward effects of the anesthesia or the surgery should be noted.

5. Allergies: Reactions to medications should be recorded, including severity and temporal relationship to the medication. An adverse effect (eg, nausea) should be differentiated from a true allergic reaction.

6. Medications: Current and previous medications should be listed, including dosage, route, frequency, and duration of use. Prescription, over-the-counter, and herbal medications are all relevant. Patients often forget their complete medication list; thus, asking each patient to bring in all their medications—both prescribed and nonprescribed—allows for a complete inventory.

7. Family history: Many conditions are inherited or are predisposed in family members. The age and health of siblings, parents, grandparents, and others can provide diagnostic clues. For instance, an individual with first-degree family members with early-onset coronary heart disease is at risk for cardiovascular disease.

8. Social history: This is one of the most important parts of the history in that the patient’s functional status at home, social and economic circumstances, and goals and aspirations for the future are often the critical determinant in what the best way to manage a patient’s medical problem is. Living arrangements, economic situations, and religious affiliations may provide important clues for puzzling diagnostic cases or suggest the acceptability of various diagnostic or therapeutic options. Marital status and habits such as alcohol, tobacco, or illicit drug use may be relevant as risk factors for disease. More specifically in the domain of infectious diseases, understanding how many people the patient cohabitates with, whether those people are known to be sick, the presence of pets at home, and the recent travel history are noteworthy.

9. Review of systems: A few questions about each major body system ensure that problems will not be overlooked. The clinician should avoid the mechanical “rapid-fire” questioning technique that discourages patients from answering truthfully because of fear of “annoying the doctor.”

PHYSICAL EXAMINATION

The physical examination begins as one is taking the history, by observing the patient and beginning to consider a differential diagnosis. When performing the physical examination, one focuses on body systems suggested by the differential diagnosis and performs tests or maneuvers with specific questions in mind; for example, does the patient with jaundice have ascites? When the physical examination is performed with potential diagnoses and expected physical findings in mind (“one sees what one looks for”), the utility of the examination in adding to diagnostic yield is greatly increased, as opposed to an unfocused “head-to-toe” physical examination.

1. General appearance: A great deal of information is gathered by observation, as one notes the patient’s body habitus, state of grooming, nutritional status, level of anxiety (or perhaps inappropriate indifference), degree of pain or comfort, mental status, speech patterns, and use of language. This forms your impression of “who this patient is.”

2. Vital signs: Vital signs like temperature, blood pressure, heart rate, respiratory rate, height, and weight are often placed here. Blood pressure can sometimes be different in the two arms; initially, it should be measured in both arms. In patients with suspected hypovolemia, pulse and blood pressure should be taken in lying and standing positions to look for orthostatic hypotension. It is quite useful to take the vital signs oneself, rather than relying upon numbers gathered by ancillary personnel using automated equipment, because important decisions regarding patient care are often made using the vital signs as an important determining factor.

3. Head and neck examination: Facial or periorbital edema and pupillary responses should be noted. Fundoscopic examination provides a way to visualize the effects of diseases such as diabetes on the microvasculature; papilledema can signify increased intracranial pressure. Estimation of jugular venous pressure is very useful to estimate volume status. The thyroid should be palpated for a goiter or nodule and carotid arteries auscultated for bruits. Cervical (common) and supraclavicular (pathologic) nodes should be palpated.

4. Breast examination: Inspect for symmetry and for skin or nipple retraction with the patient’s hands on her hips (to accentuate the pectoral muscles) and also with arms raised. With the patient sitting and supine, the breasts should then be palpated systematically to assess for masses. The nipple should be assessed for discharge, and the axillary and supraclavicular regions should be examined for adenopathy.

5. Cardiac examination: The point of maximal impulse should be ascertained for size and location, and the heart should be auscultated at the apex and at the base. Heart sounds, murmurs, and clicks should be characterized. Murmurs should be classified according to intensity, duration, timing in the cardiac cycle, and changes with various maneuvers. Systolic murmurs are very common and often physiologic; diastolic murmurs are uncommon and usually pathologic. The patient’s body habitus and the environmental noise limit the quality of the heart auscultation; always search for a quiet place to examine the patient’s heart.

6. Pulmonary examination: The lung fields should be examined systematically and thoroughly. Wheezes, rales, rhonchi, and bronchial breath sounds should be recorded. Percussion of the lung fields may be helpful in identifying the hyperresonance of tension pneumothorax or the dullness of consolidated pneumonia or a pleural effusion.

7. Abdominal examination: The abdomen should be inspected for scars, distension, or discoloration (eg, the Grey Turner sign of discoloration at the flank areas indicating intra-abdominal or retroperitoneal hemorrhage). Auscultation of bowel sounds can identify normal versus high pitched and hyperactive versus hypoactive. Percussion of the abdomen can be utilized to assess the size of the liver and spleen and to detect ascites by noting shifting dullness. Careful palpation should begin initially away from the area of pain, involving one hand on top of the other, to assess for masses, tenderness, and peritoneal signs. Tenderness should be recorded on a scale (eg, 1–4 where 4 is the most severe pain). Guarding, and whether it is voluntary or involuntary, should be noted.

8. Back and spine examination: The back should be assessed for symmetry, tenderness, and masses. The flank regions are particularly important to assess for pain on percussion, which might indicate renal disease.

9. Genitalia:

   1. Females: The pelvic examination should include an inspection of the external genitalia and, with the speculum, evaluation of the vagina and cervix. A Papanicolaou test (Pap smear) and/or cervical cultures may be obtained. A bimanual examination to assess the size, shape, and tenderness of the uterus and adnexa is important.

   2. Males: An inspection of the penis and testes is performed. Evaluation for masses, tenderness, and lesions is important. Palpation for hernias in the inguinal region with the patient standing and coughing to increase intra-abdominal pressure is useful.

10. Rectal examination: A digital rectal examination is generally performed for those individuals with possible colorectal disease or gastrointestinal bleeding. Masses should be assessed, and stool for occult blood should be tested. In men, the prostate gland can be assessed for enlargement and for nodules.

11. Extremities: An examination for joint effusions, tenderness, edema, and cyanosis may be helpful. Clubbing of the nails might indicate pulmonary diseases such as lung cancer or chronic cyanotic heart disease.

12. Neurologic examination: Patients who present with neurologic complaints usually require a thorough assessment, including mental status, cranial nerves, motor strength, sensation, and reflexes.

13. Skin examination: The skin should be carefully examined for evidence of pigmented lesions (melanoma), cyanosis, or rashes that may indicate systemic disease (malar rash of systemic lupus erythematosus).

LABORATORY AND IMAGING ASSESSMENT

1. Laboratory:

   1. Complete blood count (CBC): The CBC is used to assess for anemia and thrombocytopenia.

   2. Serum chemistry: A chemistry panel is most commonly used to evaluate renal and liver function, as well as glucose levels.

   3. Hemoglobin A_1c: this fraction of the total hemoglobin represents the addition of glucose residues, which is proportional to the serum glucose levels, but more stable than they are, thus providing with a more thorough assessment of the control of diabetes mellitus.

   4. Lipid panel: The lipid panel is particularly relevant in cardiovascular diseases.

   5. Urinalysis: Urinalysis is often referred to as a “liquid renal biopsy” because the presence of cells, casts, protein, or bacteria provides clues about underlying glomerular or tubular diseases.

   6. Infection: Gram stain and culture of urine, sputum, and cerebrospinal fluid, as well as blood cultures, are frequently useful to isolate the cause of infection.

2. Imaging procedures:

   1. Chest radiography: Chest radiography is extremely useful in assessing cardiac size and contour, chamber enlargement, pulmonary vasculature and infiltrates, and the presence of pleural effusions.

   2. Ultrasonographic examination: Ultrasonographic examination is useful for identifying fluid-solid interfaces and for characterizing masses as cystic, solid, or complex. It is also very helpful in evaluating the biliary tree, kidney size, and evidence of ureteral obstruction and can be combined with Doppler flow to identify deep venous thrombosis. Ultrasonography is noninvasive and has no radiation risk, but it cannot be used to penetrate through bone or air and is less useful in obese patients.

      CLINICAL PEARL

      • Ultrasonography is helpful in evaluating the biliary tree, looking for ureteral obstruction, and evaluating vascular structures, but it has limited utility in obese patients.

   3. Computed tomography: Computed tomography (CT) is helpful in possible intracranial bleeding, abdominal and/or pelvic masses, and pulmonary processes and may help to delineate the lymph nodes and retroperitoneal disorders. CT exposes the patient to radiation and requires the patient to be immobilized during the procedure. Generally, CT requires administration of a radiocontrast dye, which can be nephrotoxic.

   4. Magnetic resonance imaging: Magnetic resonance imaging (MRI) identifies soft-tissue planes very well and provides the best imaging of the brain parenchyma. When used with gadolinium contrast (which is not nephrotoxic), MR angiography (MRA) is useful for delineating vascular structures. MRI does not use radiation, but the powerful magnetic field prohibits its use in patients with ferromagnetic metal in their bodies, for example, many prosthetic devices.

   5. Cardiac procedures:

      1. Echocardiography: Echocardiography uses ultrasonography to delineate the cardiac size, function, ejection fraction, and presence of valvular dysfunction.

      2. Angiography: Radiopaque dye is injected into various vessels, and radiographs or fluoroscopic images are used to determine the vascular occlusion, cardiac function, or valvular integrity.

      3. Stress treadmill tests: Individuals at risk for coronary heart disease are monitored for blood pressure, heart rate, and chest pain, and an electrocardiogram (ECG) is performed while increasing oxygen demands on the heart, such as running on a treadmill, are made. Nuclear medicine imaging of the heart can be added to increase the sensitivity and specificity of the test. Individuals who cannot run on the treadmill (eg, those with severe arthritis) may be given medications such as adenosine or dobutamine to “stress” the heart.

INTERPRETATION OF TEST RESULTS: USING PRETEST PROBABILITY AND LIKELIHOOD RATIO

Because no test is 100% accurate, it is essential when ordering a test to have some knowledge of the test’s characteristics, as well as how to apply the test results to an individual patient’s clinical situation. Let us use the example of a patient with chest pain. The first diagnostic concern of most patients and physicians regarding chest pain is angina pectoris, that is, the pain of myocardial ischemia caused by coronary insufficiency. Distinguishing angina pectoris from other causes of chest pain relies upon two important factors: the clinical history and an understanding of how to use objective testing. In making the diagnosis of angina pectoris, the clinician must establish whether the pain satisfies the three criteria for typical anginal pain: (1) retrosternal in location, (2) precipitated by exertion, and (3) relieved within minutes by rest or nitroglycerin. Then, the clinician considers other factors, such as patient age and other risk factors, to determine a pretest probability for angina pectoris.

After a pretest probability is estimated by applying some combination of statistical data, epidemiology of the disease, and clinical experience, the next decision is whether and how to use an objective test. A test should only be ordered if the results would change the posttest probability high enough or low enough in either direction that it will affect the decision-making process. For example, a 21-year-old woman with chest pain that is not exertional and not relieved by rest or nitroglycerin has a very low pretest probability of coronary artery disease (CAD), and any positive results on a cardiac stress test are very likely to be false positive. Any test result is unlikely to change her management; thus, the test should not be obtained. Similarly, a 69-year-old diabetic smoker with a recent coronary angioplasty who now has recurrent episodes of typical angina has a very high pretest probability that the pain is a result of myocardial ischemia. One could argue that a negative cardiac stress test is likely to be falsely negative, and that the clinician should proceed directly to a coronary angiography to assess for a repeat angioplasty. Diagnostic tests, therefore, are usually most useful for those patients in the midranges of pretest probabilities in whom a positive or negative test will move the clinician past some decision threshold.

In the case of diagnosing a patient with atherosclerotic CAD, one test that is frequently used is the exercise treadmill test. Patients are monitored on an ECG while they perform graded exercise on a treadmill. A positive test is the development of ST-segment depression during the test; the greater the degree of ST depression, the more useful the test becomes in raising the posttest probability of CAD. In the example illustrated by Figure I–1, if a patient has a pretest probability of CAD of 50%, then the test result of 2 mm of ST-segment depression raises the posttest probability to 90%.

If one knows the sensitivity and specificity of the test used, one can calculate the likelihood ratio of the positive test as sensitivity/(1 – specificity). Posttest probability is calculated by multiplying the positive likelihood ratio by the pretest probability, or plotting the probabilities using a nomogram (see Figure I–1).

Thus, knowing something about the characteristics of the test you are employing and how to apply them to the patient at hand are essential in reaching a correct diagnosis and to avoid falling into the common trap of “positive test = disease” and “negative test = no disease.” Stated another way, tests do not make diagnoses; providers do, considering test results quantitatively in the context of their clinical assessment.

Part 2. Approach to Clinical Problem-Solving

There are typically four distinct steps to the systematic solving of clinical problems:

1. Making the diagnosis

2. Assessing the severity of the disease (stage)

3. Rendering a treatment based on the stage of the disease

4. Following the patient’s response to the treatment

MAKING THE DIAGNOSIS

There are two ways to make a diagnosis. Experienced clinicians often make a diagnosis very quickly using pattern recognition, that is, the features of the patient’s illness match a scenario the provider has seen before. If it does not fit a readily recognized pattern, then one has to undertake several steps in diagnostic reasoning:

1. The first step is to gather information with a differential diagnosis in mind. The clinician should start considering diagnostic possibilities with initial contact with the patient; these possibilities are continually refined as information is gathered. Historical questions and physical examination tests and findings are all tailored to the potential diagnoses one is considering. This is the principle that “you find what you are looking for.” When one is trying to perform a thorough head-to-toe examination, for instance, without looking for anything in particular, one is much more likely to miss findings.

2. The next step is to try to move from subjective complaints or nonspecific symptoms to focus on objective abnormalities in an effort to conceptualize the patient’s objective problem with the greatest specificity one can achieve. For example, a patient may come to the physician complaining of pedal edema, a relatively common and nonspecific finding. Laboratory testing may reveal that the patient has renal failure, a more specific cause of the many causes of edema. Examination of the urine may then reveal red blood cell casts, indicating glomerulonephritis, which is even more specific as the cause of the renal failure. The patient’s problem, then, described with the greatest degree of specificity, is glomerulonephritis. The clinician’s task at this point is to consider the differential diagnosis of glomerulonephritis rather than that of pedal edema.

3. The last step is to look for discriminating features of the patient’s illness. This means the features of the illness, which by their presence or their absence narrow the differential diagnosis. This is often difficult for junior learners because it requires a well-developed knowledge base of the typical features of disease so the diagnostician can judge how much weight to assign to the various clinical clues present. For example, in the diagnosis of a patient with a fever and productive cough, the finding by chest x-ray of bilateral apical infiltrates with cavitation is highly discriminatory. There are few illnesses besides tuberculosis that are likely to produce that radiographic pattern. A negatively predictive example is a patient with exudative pharyngitis who also has rhinorrhea and cough. The presence of these features makes the diagnosis of streptococcal infection unlikely as the cause of the pharyngitis. Once the differential diagnosis has been constructed, the clinician uses the presence of discriminating features, knowledge of patient risk factors, and the epidemiology of diseases to decide which potential diagnoses are most likely.

Once the most specific problem has been identified and a differential diagnosis of that problem is considered using discriminating features to order the possibilities, the next step is to consider using diagnostic testing, such as laboratory, radiologic, or pathologic data, to confirm the diagnosis. Quantitative reasoning in the use and interpretation of tests was discussed in Part 1. Clinically, the timing and effort with which one pursues a definitive diagnosis using objective data depend on several factors: the potential gravity of the diagnosis in question, the clinical state of the patient, the potential risks of diagnostic testing, and the potential benefits or harms of empiric treatment. For example, if a young man is admitted to the hospital with bilateral pulmonary nodules on chest x-ray, there are many possibilities, including metastatic malignancy, and aggressive pursuit of a diagnosis is necessary, perhaps including a thoracotomy with an open-lung biopsy. The same radiographic findings in an elderly bed-bound woman with advanced Alzheimer dementia who would not be a good candidate for chemotherapy might be best left alone without any diagnostic testing. Decisions like this are difficult, require solid medical knowledge, as well as a thorough understanding of one’s patient and the patient’s background and inclinations. Thus, this combination of skills constitute the art of medicine.

ASSESSING THE SEVERITY OF THE DISEASE

After ascertaining the diagnosis, the next step is to characterize the severity of the disease process; in other words, it is describing “how bad” a disease is. There is usually prognostic or treatment significance based on the stage. With malignancy, this is done formally by cancer staging. Most cancers are categorized from stage I (localized) to stage IV (widely metastatic). Some diseases, such as congestive heart failure, may be designated as mild, moderate, or severe based on the patient’s functional status, that is, their ability to exercise before becoming dyspneic. With some infections, such as syphilis, the staging depends on the duration and extent of the infection and follows along the natural history of the infection (ie, primary syphilis, secondary, latent period, and tertiary/neurosyphilis).

RENDERING A TREATMENT BASED ON THE STAGE OF THE DISEASE

Many illnesses are stratified according to severity because prognosis and treatment often vary based on the severity. If neither the prognosis nor the treatment was affected by the stage of the disease process, there would not be a reason to subcategorize as mild or severe. As an example, a man with mild chronic obstructive pulmonary disease (COPD) may be treated with inhaled bronchodilators as needed and advice for smoking cessation. However, an individual with severe COPD may need round-the-clock oxygen supplementation, scheduled bronchodilators, and possibly oral corticosteroid therapy.

The treatment should be tailored to the extent or “stage” of the disease. In making decisions regarding treatment, it is also essential that the clinician identify the therapeutic objectives. When patients seek medical attention, it is generally because they are bothered by a symptom and want it to go away. When clinicians institute therapy, they often have several other goals besides symptom relief, such as prevention of short- or long-term complications or a reduction in mortality. For example, patients with congestive heart failure are bothered by the symptoms of edema and dyspnea. Salt restriction, loop diuretics, and bed rest are effective at reducing these symptoms. However, heart failure is a progressive disease with high mortality, so other treatments, such as angiotensin-converting enzyme inhibitors and some beta-blockers, are also used to reduce mortality in this condition. It is essential that the clinician know what the therapeutic objective is so that one can monitor and guide therapy.

FOLLOWING THE PATIENT’S RESPONSE TO THE TREATMENT

The final step in the approach to disease is to follow the patient’s response to the therapy. The “measure” of response should be recorded and monitored. Some responses are clinical, such as the patient’s abdominal pain, temperature, or pulmonary examination. Obviously, the student must work on being more skilled in eliciting the data in an unbiased and standardized manner. Other responses may be followed by imaging tests, such as CT scan of a retroperitoneal node size in a patient receiving chemotherapy, or a tumor marker such as the prostate-specific antigen (PSA) level in a man receiving chemotherapy for prostatic cancer. For syphilis, it may be the nonspecific treponemal antibody test rapid plasma reagent (RPR) titer over time. The student must be prepared to know what to do if the measured marker does not respond according to what is expected. Is the next step to re-treat, to repeat the metastatic workup, or to follow up with another more specific test?

Part 3. Approach to Reading

The clinical problem-oriented approach to reading is different from the classic “systematic” research of a disease. Patients rarely present with a clear diagnosis; hence, the student must become skilled in applying the textbook information to the clinical setting. Furthermore, one retains more information when one reads with a purpose. In other words, the student should read with the goal of answering specific questions. There are several fundamental questions that facilitate clinical thinking. These questions are as follows:

1. What is the most likely diagnosis?

2. What should be the next step?

3. What is the most likely mechanism for this process?

4. What are the risk factors for this condition?

5. What are the complications associated with the disease process?

6. What is the best therapy?

7. How would you confirm the diagnosis?

WHAT IS THE MOST LIKELY DIAGNOSIS?

The method of establishing the diagnosis was discussed in the previous part. One way of attacking this problem is to develop standard “approaches” to common-clinical problems. It is helpful to understand the most common causes of various presentations, such as “the most common causes of pancreatitis are gallstones and alcohol.” (See the Clinical Pearls at end of each case.)

The clinical scenario would entail something such as

A 28-year-old pregnant woman complains of severe epigastric pain radiating to the back, nausea and vomiting, and an elevated serum amylase level. What is the most likely diagnosis?

With no other information to go on, the student would note that this woman has a clinical diagnosis of pancreatitis. Using the “most common cause” information, the student would make an educated guess that the patient has gallstones, because being female and pregnant are risk factors. If, instead, cholelithiasis is removed from the equation of this scenario, a phrase may be added, such as

“The ultrasonogram of the gallbladder shows no stones.”

Now, the student would use the phrase, “patients without gallstones who have pancreatitis most likely abuse alcohol.” Aside from these two causes, there are many other etiologies of pancreatitis.

WHAT SHOULD BE THE NEXT STEP?

The question, “what is the next step” is difficult because the next step may be more diagnostic information, staging, or therapy. It may be more challenging than “the most likely diagnosis” because there may be insufficient information to make a diagnosis, and the next step may be to pursue more diagnostic information. Another possibility is that there is enough information for a probable diagnosis, and the next step is to stage the disease. Finally, the most appropriate action may be to treat. Hence, from clinical data, a judgment needs to be rendered regarding how far along one is on this road:

Frequently, the student is taught to regurgitate the same information that someone has written about a particular disease but is not skilled at giving the next step. This talent is learned optimally at the bedside, in a supportive environment, with freedom to make educated guesses, and with constructive feedback. A sample scenario may describe a student’s thought process as follows:

1. Make the diagnosis: “Based on the information I have, I believe that Mr. Smith has stable angina because he has retrosternal chest pain when he walks three blocks, but it is relieved within minutes by rest and with sublingual nitroglycerin.”

2. Stage the disease: “I don’t believe that this is severe disease because he does not have pain lasting for more than 5 minutes, angina at rest, or congestive heart failure.”

3. Treatment based on stage: “Therefore, my next step is to treat with aspirin, beta-blockers, and sublingual nitroglycerin as needed, as well as lifestyle changes.”

4. Follow response: “I want to follow the treatment by assessing his pain (I will ask him about the degree of exercise he is able to perform without chest pain), performing a cardiac stress test, and reassessing him after the test is done.”

In a similar patient, when the clinical presentation is unclear or more severe, perhaps the best “next step” may be diagnostic in nature, such as a thallium stress test or even coronary angiography. The next step depends upon the clinical state of the patient (if unstable, the next step is therapeutic), the potential severity of the disease (the next step may be staging), or the uncertainty of the diagnosis (the next step is diagnostic).

Usually, the vague question, “What is your next step?” is the most difficult question because the answer may be diagnostic, staging, or therapeutic.

WHAT IS THE MOST LIKELY MECHANISM FOR THIS PROCESS?

The question of the most likely mechanism for the process not only goes further than making the diagnosis, but it also requires the student to understand the underlying mechanism for the process. For example, a clinical scenario may describe an “18-year-old woman who presents with several months of severe epistaxis, heavy menses, petechiae, and a normal CBC except for a platelet count of 15,000/mm³.” Answers that a student may consider to explain this condition include immune-mediated platelet destruction, drug-induced thrombocytopenia, bone marrow suppression, and platelet sequestration as a result of hypersplenism.

The student is advised to learn the mechanisms for each disease process and not merely memorize a constellation of symptoms. In other words, rather than solely committing to memory the classic presentation of idiopathic thrombocytopenic purpura (ITP) (isolated thrombocytopenia without lymphadenopathy or offending drugs), the student should understand that ITP is an autoimmune process whereby the body produces immunoglobulin (Ig) G antibodies against the platelets. The platelet-antibody complexes are then taken from the circulation in the spleen. Because the disease process is specific for platelets, the other two cell lines (erythrocytes and leukocytes) are normal. Also, because the thrombocytopenia is caused by excessive platelet peripheral destruction, the bone marrow will show increased megakaryocytes (platelet precursors). Hence, treatment for ITP includes oral corticosteroid agents to decrease the immune process of antiplatelet IgG production, and, if refractory, then splenectomy.

WHAT ARE THE RISK FACTORS FOR THIS PROCESS?

Understanding the risk factors helps the practitioner to establish a diagnosis and to determine how to interpret tests. For example, understanding the risk factor analysis may help to manage a 45-year-old obese woman with sudden onset of dyspnea and pleuritic chest pain following an orthopedic surgery for a femur fracture. This patient has numerous risk factors for deep venous thrombosis and pulmonary embolism. The clinician may want to pursue angiography even if the ventilation/perfusion scan result is low probability. Thus, the number of risk factors helps to categorize the likelihood of a disease process.

For infrequent diseases (eg, lung cancer), the risk factors are identified as odds ratios: These represent the probability of the event (lung cancer) in the presence of an exposure (smoking), divided by that probability in absence of the exposure. We know now not only that smoking is more common in patients with lung cancer, but also the mechanisms that explain the causality. Nevertheless, odds ratios can be explained as follows: If your patient has lung cancer, it is more likely that he or she smokes than he or she does not. Most smokers do not have lung cancer.

WHAT ARE THE COMPLICATIONS ASSOCIATED WITH THE DISEASE PROCESS?

A clinician must understand the complications of a disease so that one may monitor the patient. Sometimes, the student has to make the diagnosis from clinical clues and then apply his or her knowledge of the sequelae of the pathologic process. For example, the student should know that chronic hypertension may affect various end organs, such as the brain (encephalopathy or stroke), the eyes (vascular changes), the kidneys, and the heart. Understanding the types of consequences also helps the clinician to be aware of the dangers to a patient. The clinician is acutely aware of the need to monitor for the end-organ involvement and undertakes the appropriate intervention when involvement is present.

WHAT IS THE BEST THERAPY?

To answer this question, the clinician needs to reach the correct diagnosis, assess the severity of the condition, and weigh the situation to reach the appropriate intervention. For the student, knowing exact dosages is not as important as understanding the best medication, route of delivery, mechanism of action, and possible complications. It is important for the student to be able to verbalize the diagnosis and the rationale for the therapy. A common error is for the student to “jump to a treatment,” like a random guess, and therefore be given “right or wrong” feedback. In fact, the student’s guess may be correct, but for the wrong reason; conversely, the answer may be a very reasonable one, with only one small error in thinking. Instead, the student should verbalize the steps so that feedback may be given at every reasoning point.

For example, if the question is, “What is the best therapy for a 25-year-old man who complains of a nontender penile ulcer?” the incorrect manner of response is for the student to blurt out “azithromycin.” Rather, the student should reason it out in a way similar to this: “The most common cause of a nontender infectious ulcer of the penis is syphilis. Nontender adenopathy is usually associated. Therefore, the best treatment for this man with probable syphilis is intramuscular penicillin (but I would want to confirm the diagnosis). His partner also needs treatment.”

Frequently, clinicians face the need for rapid decision-making. With little evidence in their hands, they need to decide whether an acutely ill-appearing patient needs treatment for a likely, yet unproven, diagnosis. The clinician’s experience plays an essential role in deciding when to start a treatment before the final diagnosis is established.

HOW WOULD YOU CONFIRM THE DIAGNOSIS?

In the previous scenario, the man with a nontender penile ulcer is likely to have syphilis. Confirmation may be achieved by serology (RPR or Venereal Disease Research Laboratory [VDRL] test); however, there is a significant possibility that patients with primary syphilis may not have developed antibody response yet and have negative serology. Thus, confirmation of the diagnosis is attained with dark-field microscopy. Knowing the limitations of diagnostic tests and the manifestations of disease aids in this area.

SUMMARY

1. There is no replacement for a careful history and physical examination.

2. There are four steps to the clinical approach to the patient: making the diagnosis, assessing severity, treatment based on severity, and following response.

3. Assessment of pretest probability and knowledge of test characteristics are essential in the application of test results to the clinical situation.

4. There are seven questions that help to bridge the gap between the textbook and the clinical arena.

References