Basically, the purpose of medical diagnosis is to determine the illness of the patient. It is based on the clinician’s judgment on what is the patient’s condition. A diagnosis is only formed when enough data are required. There are many types of data. There is the subjective data, which includes the history of the illness, past medical history, family history, personal history, social history and a review of systems. Sometimes, it also includes diet history and travel history. It is anything that a clinician that may find pertinent. Objective data, on the other hand, is the actual physical and laboratory examination that the doctor does. It is objective in the sense that the data gathered would be the evidence of the disease.
Outcomes of the diagnosis however are not always 100%. My brother, who is a medical student, told me that they have to think of differentials. It is possible to have possible same signs, symptoms and laboratory results that can be replicated by some other disease entry. He made Pulmonary Tuberculosis (Pulmo TB) here in the Philippines as an example. He said that Pulmo TB is so rampant here in the Philippines to the point that clinicians diagnose this quickly as long as the patient has chronic cough, afternoon fever, chills and probably weight loss, for laboratory, chest x-ray and sputum acid fast bacilli will be requested. Apparently, somewhere in the Visayas region, there is a disease entity that presents exactly the same as Pulmo TB. They have the same symptoms but this one has a negative laboratory results and not to mention that TB meds don’t respond to the patient. It was concluded that the disease is parasitic.
Therefore we can say that the limitations of diagnosis are:
1. Some clinicians are too dependent on the data given by the patient. 80-90% of the time, they have a diagnosis in their heads based on the history alone.
In the episode of House, this is seen on the farmer. He told the doctors that a snake bit him, but in truth, his dog bit him. Therefore, this leaded to the doctor’s wrong diagnosis.
2. The diagnosis is totally dependent on the statistics of each disease entity. Clinicians would always think of the most common diseases before considering a rare one.
In the episode of House, this is seen on the volleyball player. They thought it was just an ordinary tendinitis and her thyroid problems. The medication given doesn’t work and she develops other symptoms. More tests were done and it was revealed that she had a cancerous tumor on her femur.
3. The patient’s financial capacities. Not everyone is blessed to have enough money for him or her to pay the examinations needed to produce data for an accurate diagnosis.
4. There is what we call false-positives and false-negatives. This is only capable when they are only laboratory dependent to figure out the diagnosis. While there are gold standard tests in figuring out that you have a certain disease, usually it is a hassle to do because its either its too expensive or its going to take a long time before they get the results. This is difficult because there would be cases that by the time the results are out, it’s already too late. So we are left to rely on other less expensive tests but they are not 100% accurate in diagnosing the disease.