What is “screening” in medicine?
Screening is based upon the simple idea that results of treatment of a disease are better – i.e. lower chance of death, faster recovery, fewer complications, less disability, less expense – when disease has been diagnosed at an early stage, before it has caused permanent damage.
There are many ways to screen.
COVID screening is a recent example of how this process works. COVID screening is not one single test, but rather represents a process, relying on multiple steps.
The first step is to ask questions. A person is asked about risk factors, for example have they recently traveled to another country? Have they been in contact with a person infected with COVID?
The next step is to screen for fever with a thermometer.
If the patient has a fever, or has had contact with a sick patient, then the risk of COVID is higher and the next step in the process is to test for COVID virus by nasopharyngeal swab.
If the COVID infection diagnosis can be made at this stage, before pneumonia and sepsis force hospitalization, treatment can be begun with antiviral drugs and or convalescent serum. Both of these treatments lower chance of hospitalization, complications and death.
If these treatments are given only after the patient has become so sick that hospitalization in an ICU is required or ventilator support is needed, then medical treatments have less effectiveness and the chance of death or major complications is much higher.
Everyone is familiar with many other forms of medical screening.
When the doctor feels your pulse they are screening for cardiac arrhythmia.
A blood pressure measurement is a screen for hypertension.
A weight measurement screens for obesity.
You are asked to read an eye chart to screen for vision loss.
A tonometer placed on your eyeball screens for glaucoma.
There are literally hundreds of other screens that a patient goes through in the course of medical care. There is nothing exotic or intrusive about screening in medicine.
Screening can also take place in laboratory testing.
A urine specimen can be used to screen for diabetes, kidney disease, pregnancy and other conditions.
“Routine” blood tests screen for anemia, diabetes, hyper cholesterolemia, hepatitis, kidney disease, AIDS and other diseases.
Screening can also be carried out using x-rays and other imaging tests. Chest x-rays were used extensively for tuberculosis in past years, when that disease was more common in the U.S. . Pregnant women undergo ultrasound examinations to ensure that the fetus is safe.
The reason that I give so many examples of screening is that, in recent years, some doctors have attacked screening, pushing forward the idea that there are major harms to screening, particularly in the case of cancer screening.
The potential risks of medical screening will be discussed further in future blogs.