Although primary prevention is most effective and efficient, sometimes things slip through cracks in our primary prevention efforts. Secondary prevention refers to our efforts to detect a disease early before one has developed symptoms from it, and prevent it from getting worse or spreading to others. Secondary prevention is often referred to as screening. For example, each time you visit a doctor your weight, blood pressure, and pulse are generally measured. This is done to detect any abnormalities or changes even if you don’t feel any symptoms related to those changes. Sexually active women are screened for cervical cancer with a Papanicalou test. We screen pregnant women for anemia, inadequate weight gain, high blood pressure, and several other problems that would impact the health of the mother and the fetus. We check newborns for various indicators of diseases that may not become apparent until they are older but have significant implications for their growth and development. We screen growing children for evidence of any delay in reaching their developmental milestones. These could be indicators of not only physiological problems but even psychosocial problems. In some countries teenagers and young adults are screened for depression, problems at school, tobacco, alcohol, and drug use, and sexually transmitted diseases. Some societies screen people for vision problems and glaucoma. Some recommend regular dental check-ups to detect tooth and gum disease early before people develop bleeding gums or tooth abscesses. People in occupations that carry a high risk of exposure to a toxic agent are often screened for early signs of disease before the worker may be aware of any problem. Examples of secondary prevention programs in the workplace include hearing screening in noisy workplaces or blood lead levels in workers who handle lead. Hospitals and schools often screen their employees for infectious diseases such as tuberculosis in order to catch the disease in an employee who might not have any symptoms to prevent the spread of tuberculosis to others. Workplaces sometimes screen employees for drugs of abuse, particularly if job performance has an impact on the safety of the public. Pilots, commercial truck drivers, and air traffic controllers are examples of workers who must be very alert and conscientious in their duties to prevent accidents. The effects of using drugs and alcohol can impact job performance even if the worker is not intoxicated while on duty. Many airports are now screening all passengers for items which could be used as weapons. This measure doesn’t prevent anyone from having bad intentions. It is an attempt to prevent someone from carrying out harm once the intention has already developed. In this scenario primary prevention efforts would involve measures that create harmonious and friendly relations with all people and all nations so that nobody would want to harm others.
Most secondary prevention efforts are aimed at selective groups. It is highly inefficient to screen the whole entire population of the world for every possible disease. Not all women need to get a Papanicalou test, only women who are at high risk for developing cervical cancer. Everyone in the world doesn’t need to have a screening colonoscopy to detect colon cancer or a mammogram to detect breast cancer. It only makes sense for those at high risk. In fact, if one is not at risk for getting a disease or at very low risk then the possibilities of having complications from the screening test may be greater than the chance of getting the disease itself. Of course some screening tests are very low risk, like screening for depression or tobacco, alcohol, or drug abuse.