How a Diagnosis Works

Have you ever wondered how a doctor comes up with a diagnosis for his or her patients? In today’s world of MRI’s, lasers, and high technology, it may surprise you to learn that the basics of how to determine what is wrong with a person dates back thousands of years ago, with the Greeks. One of the most prominent and influential of the ancient physicians was Hippocrates. His systematic approach to the diagnosis and treatment of patients nearly twenty-five centuries ago, helped to set the foundation for how doctors approach their patients today.
Normal or Abnormal?

The first thing a doctor must discover when treating a patient is whether a condition is physiologic or pathologic. What this means is that the doctor must determine if the condition is normal or associated with disease. To illustrate this point, a patient came into my office a while back very concerned about a “growth” on the back of her head, behind the ear. She had never noticed it before. I examined the area and found that she did indeed have a firm mass behind the ear. Fortunately, she had a similar mass behind the other ear, and what she was concerned about was a normal part of the anatomy of her skull, the mastoid process. This would therefore be considered a normal, physiologic condition, and require no treatment.

So, how does a doctor determine whether a condition is pathologic, and therefore requires treatment? This is where the ancient Greeks have contributed to our understanding of diagnosis and treatment of disease. To determine if a condition requires treatment, the doctor must ask himself or herself the following questions: “Does disease presently exist?” and “Will disease occur if no treatment is given?” If the answer is yes to either of these questions, we will then have a condition that requires treatment. It is important to note that in most cases, a doctor must also know the natural history of a disease to answer these questions. A good example is found in the venereal disease Syphilis. In the primary stage, a sore called a chancre forms, and then “heals” on its own. Shortly following this stage, rashes appear, and then also, often “heal” on their own. Several years later, a wide variety of ailments can occur, such as the formation of a lesion called gumma (an inflammatory mass that destroys tissue), as well as cardiovascular and neurologic disease processes. So if a patient comes to the doctor with a syphilis chancre sore, this represents both a disease that presently exists, and a process that will cause further disease if no treatment is given. Therefore, syphilis obviously represents a pathologic condition that requires treatment.
When a doctor examines a patient, what he or she is trying to discover is the correct diagnosis. The correct diagnosis is called the definitive diagnosis, which is garnered from a list of potential diagnoses called the differential diagnosis (the differential). The process of narrowing down the differential diagnosis involves a series of steps that often leads to the correct diagnosis. Those steps are represented by the mnemonic HIPPAA, which stands for history, inspection, percussion, palpation, auscultation, and additional tests.
Hippocratic Oath
I SWEAR by Apollo the physician, and Aesculapius, and Hygeia, and Panacea, and I take to witness all the gods, all the goddesses, to keep according to my ability and my judgment, I will keep this Oath and this stipulation to reckon him who taught me this Art equally dear to me as my parents, to share my substance with him, and relieve his necessities if required; to look upon his offspring in the same footing as my own brothers, and to teach them this art, if they shall wish to learn it, without fee or stipulation; and that by precept, lecture, and every other mode of instruction, I will impart a knowledge of the Art to my own sons, and those of my teachers, and to disciples bound by a stipulation and oath according to the law of medicine, but to none others. I will follow that system of regimen which, according to my ability and judgment, I consider for the benefit of my patients, and abstain from whatever is deleterious and mischievous. I will give no deadly medicine to any one if asked, nor suggest any such counsel; and in like manner I will not give to a woman a pessary to produce abortion. With purity and with holiness I will pass my life and practice my Art. I will not cut persons laboring under the stone, but will leave this to be done by men who are practitioners of this work. Into whatever houses I enter, I will go into them for the benefit of the sick, and will abstain from every voluntary act of mischief and corruption; and, further from the seduction of females or males, of freemen and slaves. Whatever, in connection with my professional practice or not, in connection with it, I see or hear, in the life of men, which ought not to be spoken of abroad, I will not divulge, as reckoning that all such should be kept secret. While I continue to keep this Oath unviolated, may it be granted to me to enjoy life and the practice of the art, respected by all men, in all times! But should I trespass and violate this Oath, may the reverse be my lot!
n some ways, the history is the most important part of the process of discovering the diagnosis. The history is information about the patient from what they tell the doctor, and is considered a subjective finding. One recent study found that the average amount of time a doctor listens to a patient before interrupting is 17 seconds. This is obviously not enough time. Doctors must spend time listening to their patients, because subtle clues and other details are critical to developing an adequate base of information to begin establishing a differential diagnosis.
Some of the things that are included in the history are the patients name, age, race, sex, chief complaint, history of present illness, past medical history, family history, social history, and the review of systems.
Name, age, race, and sex
While it may seem quite obvious why a doctor may need to know these things, there are other reasons that are not as apparent. The age and sex of a patient is important because certain diseases have a predilection for a range of age and gender. The disease multiple sclerosis, for instance, usually strikes women more often than men, and typically from age 20 to 40. Race can also be linked to the prevalence of a certain diseases. African Americans are more likely to develop Sickle Cell Anemia and Lactose Intolerance than Caucasians.
Chief Complaint
The chief complaint, sometimes known as the pain complaint, is an explanation of the patient’s problem in his or her own words. The chief complaint might be that “I wake up every night with a severe headache”, “my teeth hurt when I drink anything hot or cold”, “My fingers are so sore and painful that I can’t button my shirt without help”, etc. A detailed description of the problem is very helpful in finding out what is wrong with a patient. Over years of practice, a doctor has heard a wide range of complaints and can use this experience to help develop a differential diagnosis. In some cases, a doctor may have a good idea about what the diagnosis is from the chief complaint alone, and form what is called a “presumptive diagnosis”. This is the “gut” feeling of the doctor, who now tries to prove or disprove this preliminary diagnosis to come up with the final or definitive diagnosis.
History of present illness (HPI)
The HPI is basically a detailed description of the patient’s symptoms. The doctor needs to know, for example, what part of the body is in pain, does the pain radiate to another part of the body, when the pain started, how long does the pain last, what makes the pain more or less intense, and many other details of the symptoms. The symptoms should also be obtained in chronological order. A patient who has become out of breath climbing up the stairs to his bedroom for the last few months, and then complains of chest pains when lifting a heavy object yesterday may be giving a HPI consistent with cardiovascular disease.
Past Medical History
The past medical history is a comprehensive list of any illness a person has currently, or has had in the past, what medications (including over-the-counter) they are taking, what surgeries and hospitalizations they have had (including complications), allergies to medications and other substances, blood transfusions, and other medical tests and examinations the person may have had. The doctor needs to know these things because they can help lead to an accurate diagnosis, and also aid in the proper management of the patient. For example, a person who has had chest pain and recently had a stress test and echocardiogram that were normal and has had no medical problems in the past may lead the doctor to suspect a more innocuous condition, like indigestion instead of a more serious ailment such as Angina. However, a person who comes in with a past medical history of diabetes and hypertension, and infrequent visits to his doctor and has the same chest pain may lead to the suspicion of a more serious cardiovascular condition.
Family History
The family history includes the age, status (alive or dead), and medical problems of blood relatives. Certain diseases such as cancer, hypertension, bleeding disorders, and many others tend to “run in the family”. Generally speaking, the closer the blood relative who has a disease is, such as mother, father, brother or sister, the more likely the person is to have a predisposition to a disease. Knowing the family history of certain diseases can aid the doctor in a diagnosis.
Social History
The social history includes the patient’s marital status, children, employment (including exposure to environmental contaminants), education, economic situation, religion, hobbies, living conditions, and habits such as alcohol and tobacco use. This is important for help in the diagnosis of many different disorders. A history of alcoholism and a patient who has a yellowish tint to their skin (jaundice) may help support a diagnosis of cirrhosis of the liver. A woman that has had her first child after age thirty has a slightly higher risk of developing breast cancer. Knowing the patient’s social history can help a doctor narrow down a differential diagnosis in some cases.
Review of Systems (ROS)
The review of systems is a process where the doctor evaluates every system in the body to help determine where the disease process is occurring. These systems include general condition, skin, head, eyes, ears, nose, throat, respiratory, cardiovascular, gastrointestinal, gynecologic, genitourinary, endocrine, musculoskeletal, peripheral vascular, hematology, and neuropsychiatric. Some examples of what a doctor looks for in these systems are as follows:

  • The general condition: weight loss or gain, weakness, fever, chills, etc.
  • The ears: changes in hearing, discharge, pain, etc.
  • The gastrointestinal system: heartburn, nausea, abdominal pain, diarrhea, and other symptoms.

So, if a patient comes to the dentist with pain on the lower right side of the jaw, radiating to the ear, part of the ROS is to rule out inner ear infection if the potential cause is an infected tooth (It is possible that that patient has an infection of the tooth and the ear). The ROS helps to clarify and focus a diagnosis.
The inspection is a visual examination of the patient. There are many things you can see when looking at a patient that can help aid in a diagnosis. You can evaluate the person’s mood, bearing, race, how they walk (gait) as well as potential pathology to exposed skin (rashes, scars, moles, etc.), damage to the eye (enlarged pupils, hemorrhages, eye movements, etc.), and many other pieces of information. Most clues obtained from the inspection are not diagnostic in and of themselves, but there are exceptions. The “pill rolling” (the person will appear to roll an imaginary pill in their fingers) tremor of patients with Parkinson’s disease and the enlarged thyroid in patients with Goiter are highly suggestive of these disorders. Usually though, the inspection is just a piece of the puzzle.
Palpation, or the “laying on of hands” is an important method a doctor can use to help determine if disease exists. Palpation can locate a suspicious lump on a patient’s breast, gauge infection by examining enlargement of the lymph nodes (especially under the neck), evaluate swelling of joints and bony fractures, and a multitude of other conditions. Palpation is highly useful in discovering potential disease.
Percussion is the art of tapping on a particular part of the body to find a potential area of disease. A dull sound discovered by percussion where a hollow sound is normally expected may lead to a suspicion of a hard mass (tumor) or a fluid filled cavity. In dentistry, percussion can often identify an infected tooth, which will feel different or more painful than other teeth when tapped.
Auscultation, or listening to the sounds of the body, is often helpful in forming a diagnosis. A doctor can use a stethoscope to listen for abnormal sounds in the chest, back or abdomen. Coughing or wheezing can help to identify respiratory problems. Another example is the use of auscultation for heart murmurs and other noises called bruits that may indicate certain kinds of heart disorders.
Additional Tests
Additional tests are those that are ordered by the doctor to help support or refute a diagnosis by giving additional information. Some of the most common include:

  1. Biopsy (incisional, excisional, fine-needle aspiration, etc.)
    • Useful in identifying malignant or benign tumors, infectious diseases, and other pathological processes Imaging Studies (x-rays, MRI, Cat Scan, Ultrasound, angiograms, etc.)
    • Helps to visually identify disease or damage in hard and/or soft tissues such as tumors, bone fractures, cysts, inflammation, fluid accumulation, soft tissue injuries, congenital deformities, air emphysema, etc.
  2. Blood Studies (Complete Blood Count (CBC), platelets, differential white blood cell count, etc.)
    • Helps to identify certain cancers (e.g. Leukemia), abnormal numbers of red or white blood cells and platelets, too much or too little hemoglobin, etc.

Additional tests are usually ordered to confirm a presumptive diagnosis, eliminate an incorrect diagnosis, narrow down the differential diagnosis, or give additional clues to help arrive at a difficult definitive diagnosis.
As you can see, a doctor must use a wide variety of sources to discover what is wrong with a patient. A diagnosis is very much like a jigsaw puzzle. Each element of the HIPPAA can play an important role. In some diseases, one aspect of the HIPPAA can provide a large piece of the puzzle. Diseases like Leukemia (additional tests) and Parkinson’s disease (Inspection) are good examples. Other diseases like Lupus may prove elusive after exhausting all of the clues determined in the HIPPAA.
Fortunately, the lessons taught by the ancient Greeks coupled with modern education and technology allows doctors to solve most diagnostic dilemmas.