After doctors have completed a medical history and physical examination of the patient they will begin making educated guesses about the causes of the patient's symptoms. To properly diagnose the patient, the doctor will usually need to perform targeted diagnostic tests to gain an accurate understanding of what is and what is not causing symptoms
Failing to order a diagnostic test is one of the most common medical malpractice errors.
Screening or Diagnosis
Diagnoses come in many layers: first doctors will evaluate a patient's health by talking to the patient about her personal and family medical history, next the doctor will complete a full physical examination. After these steps, the doctor will have some idea of what might be causing symptoms in the patient. The doctor will order specific diagnostic tests to establish the presence of a disease and to rule out possible diseases.
However, doctors can also diagnose patients who are not experiencing any symptoms by using a screening test. Screening tests are used for patients who have indicators of a disease, even if the patient has not noted any symptoms of a disease.
Common screening tests include:
- Mammograms for breast cancer
- Blood pressure for hypertension
- Cholesterol for heart disease
- Blood sugar levels for diabetes
- Pap smear for cervical cancer
- Prostate Specific Antigen (PSA) test for prostate cancer
- Thyroid-Stimulating Hormone (TSH) for hyperthyroid
Screening tests are usually simple, cheap tests that can make a big difference in a patient's diagnosis. A screening test can be the difference between a diagnosis of stage 1 breast cancer and stage 4 breast cancer.
If a screening test comes out positive, the doctor will complete further diagnostic tests on the patient to establish the presence of a specific disease.
Goals of Diagnostic Tests
The main reasons to complete a diagnostic test are:
- Establish the presence of a disease in a patient experiencing symptoms
- Screen for a disease in a patient who is not experiencing symptoms
- Determine specific medical data about a diagnosis
- Monitor the progression of treatments or medications on a patient's disease
- Establish that a patient is cured and disease free
Diagnostic tests are not the first step in determining disease. They are the last step to refine a diagnosis and confirm the presence of a disease. One diagnostic test can be used for multiple purposes, and the tests may be repeated to establish that a patient is disease free. Some diagnostic tests can be used to diagnose and treat a patient simultaneously; colonoscopies can be used to both detect polyps on the intestine and to remove the polyps.
Duty to Employ Proper Lab and Diagnostic Procedures
Performing screening and diagnostic tests accurately and in a timely manner is part of a physician's basic duty. Failing to do so postpones treatment and can cause irreversible damages to a patient's health. Performing the procedures too often can also harm patients; invasive diagnostic tests like endoscopies can create excessive risks for patients who do not need them. Doctors are trained to recognize when tests are needed and they can be held liable for damages to patients when they fail their duty to properly perform diagnostic tests.
Once doctors complete diagnostic and screening tests, they must accurately report the results to patients and any other members of the patient's care team (like their general physician) that might need to know.
Before a doctor performs a diagnostic test, patients should know:
- Why the test is being performed
- How the test will be performed
- What the test is specifically looking for
- If the test is the only way to obtain needed information
- How the patient should prepare for the test
- When the patient will receive results of the test
- What will happen next after the test
Types of Diagnostic Tests
These include blood tests, urinalysis, synovial fluid (fluid around a joint), semen analysis, and many other types of tests. These samples are usually obtained by using a needle and syringe.
Imaging tests allow doctors to see inside a patient's body. These tests can be used to determine the stage of a disease, and to monitor the progress of treatments. Imaging tests are non-invasive and painless.
Examples of imaging tests include:
- Radiation or x-rays tests like CT or PET scans
- Magnetic resonance imaging (MRI) scans
- Ultrasounds and other sound wave tests
- Dyes and contrast agents used to highlight and outline organs in imaging tests
Endoscopes are thin flexible viewing tubes that doctors insert into patients' bodies to see inside. Endoscopies may be performed through the nose, mouth, or anus, or surgically through the abdomen, through joints, or through the lungs or chest.
Biopsies are small tissue samples that are removed and examined for abnormalities like cancer, inflammation, or the presence of specific abnormal cells.
Measurement of Vital Functions
Doctors may measure various vital functions in the patient like the electrical activity of the heart (ECG), or the electrical activity of the brain (EEG)
Genetic testing of the skin, blood, or bone marrow can be used to determine if a fetus possesses a genetic disorder, if a child is at risk for a disorder, or if an adult possesses a disorder that she might pass on to family.