patient scenario

B. Steps in Diagnosis

1. Taking a History of the Disease

The first step in determining a correct diagnosis is collecting the history of the symptoms starting from the most recent. Patients should have an opportunity to tell their own story. However, the physician should listen carefully and elicit all relevant information pertaining to the symptoms such as the onset, duration, and possible relief. The physician should ask appropriate questions, not only about the patient's medical history, but also about family, social, and work history because some disorders tend to run in families or are related to social behaviors or workplace conditions.

2. Physical Examination

After listening to the patient's description of the history of the symptoms, physicians generally conduct a physical examination, which includes:

· Observing the physical signs of a disease and evaluating, for example, posture, facial expression, mobility, alertness, responsiveness to stimuli, changes in skin color.

· Taking the patient's vital signs, including blood pressure, heart rate, and breathing rate, along with temperature and comparing them to the reference ranges.

· Using a stethoscope in a procedure called auscultation to listen to the lungs, heart, and bowel movement. A healthy heartbeat sounds different than a heartbeat of a heart with valve damage.

· Tapping on the chest and abdomen in a procedure called percussion produces a specific sound under normal conditions. If there is fluid or excess air in the lungs, this sound will change. By tapping along orientation lines, a physician can determine the size of the lungs and the size of the area affected by a disease. (This procedure may not be used very often.)

· Using the fingers and applying pressure in a procedure called palpation to feel the body regions and the organs within them. Palpation provides information about the size of an organ and changes in its consistency, shape, and tenderness, and can help determine the presence of a foreign mass.

The results of the physical examination allow the physician to limit the number of possible causes of the patient's disorder and order appropriate laboratory and imaging tests.

3. Investigative Tests and Procedures

Laboratory tests, ultrasound, imaging procedures, nuclear scans, and clinical procedures play important roles in differential diagnosis (a process of distinguishing between diseases with similar signs and symptoms)—that is, they allow the doctor to narrow the diagnoses (see Table 1.7).

Table 1.7 Examples of Tests and Procedures

Tests and Procedures	Examples
Laboratory tests	Complete blood count, concentration of electrolytes in blood, amount of cholesterol in plasma, glucose tolerance test, skin tests, urinalysis
Imaging techniques	Ultrasound, magnetic resonance imaging (MRI), computer tomography (CT), X-rays
Nuclear scans	Positron emission tomography (PET), thyroid scan, bone scan
Clinical procedures	Biopsy, electrocardiogram (ECG), electroencephalogram (EEG), Pap smear, endoscopy, colonoscopy

 

4. Simplified Differential Diagnosis of a Sore Throat

A sore throat is a common complaint and is most commonly caused by the viruses responsible for the common cold. Another frequent cause is a bacterial infection. According to Principles of Internal Medicine, about 15 percent of bacterial infections are caused by group A Streptococcus pyogenes (Braumwald, 2001, p. 191). Ways of determining whether a sore throat is caused by a bacterial infection or by a viral infection are shown in Table 1.8 below.

You may wonder why it is important to differentiate between viral and bacterial infections. First of all, the treatment for bacterial infections differs from the treatment for viral infections. Antibiotics are effective only for bacterial infections. Second, if the sore throat is caused by group A streptococci, an untreated infection may lead to severe complications including abscesses at the site of the infections (tonsils and throat) and rheumatic fever.

Table 1.8 Differential Diagnosis between Bacterial and Viral Infection of the Throat

	Etiology: Bacterial (streptococci, Groups A, C, and G)	Etiology: Viral (rhinovirus, coronavirus, parainfluenza virus)
History	Possible exposure in social or work setting Symptoms: sore throat, painful swallowing, tiredness, fever, and muscle ache	Possible exposure in social or work setting Symptoms: sore throat, painful swallowing, tiredness, fever, sneezing, difficulty breathing through the nose
Vital signs	Vitals within norm, possible high-grade fever	Vitals within norm, possible low-grade fever
Inspection and signs	· Red throat · Swollen tonsils · Swollen uvula · White spots on tonsils · Grayish tongue	· Red throat · Swollen tonsils
Auscultation	Heart, lungs normal	Heart, lungs normal
Percussion	Lungs, abdomen normal	Lungs, abdomen normal
Palpation	Enlarged tonsils, lymph nodes	Enlarged tonsils
Laboratory test—culture	Positive for presence of streptococci	Negative for presence of streptococci

 

Figure 1.9 displays the most common differences between sore throats caused by viral infections and sore throats caused by bacterial infections.

Figure 1.9 Differences between Bacterial and Viral Infection

Based on Cal Poly Health and Counseling Services (n.d.). Retrieved March 30, 2009, from http://www.hcs.calpoly.edu/images/tonsillitis.jpg

 

In the first part of this section, we discussed the major categories of disorders and the steps leading to a diagnosis. Now we will take a closer look at one of the most common causes of disorders—microorganisms.