In medicine, screening is a strategy used to look for as-yet-unrecognised conditions or risk markers. This testing can be applied to individuals or to a whole population without symptoms or signs of the disease being screened.

In medicine, screening is a strategy used to look for as-yet-unrecognised conditions or risk markers.[1][2][3] This testing can be applied to individuals or to a whole population without symptoms or signs of the disease being screened.

Screening interventions are designed to identify conditions which could at some future point turn into disease, thus enabling earlier intervention and management in the hope to reduce mortality and suffering from a disease. Although screening may lead to an earlier diagnosis, not all screening tests have been shown to benefit the person being screened- overdiagnosis, misdiagnosis, and creating a false sense of security are some potential adverse effects of screening. Additionally, some screening tests can be inappropriately overused.[4][5] For these reasons, a test used in a screening program, especially for a disease with low incidence, must have good sensitivity in addition to acceptable specificity.[6]

Several types of screening exist: universal (population-based) screening involves testing of all individuals in a certain category (for example, all children of a certain age). Case finding involves testing a smaller group of people based on the presence of risk factors (for example, because a family member has been diagnosed with a hereditary disease). When delivered to large numbers of people at the population level rather than by individual clinicians, testing asymptomatic people for disease because they have one or more risk factors is sometimes referred to as targeted or stratified screening.[7] Screening interventions are not designed to be diagnostic, and often have significant rates of both false positive and false negative results.

In the US, frequently updated recommendations for screening are provided by the independent panel of experts, the United States Preventive Services Task Force.[8] In the UK, recommendations are provided by the UK National Screening Committee.[9]

Principles

In 1968, the World Health Organization published guidelines on the Principles and practice of screening for disease, which is often referred to as the Wilson and Jungner criteria.[10] The principles are still broadly applicable today:

  1. The condition should be an important health problem.
  2. There should be a treatment for the condition.
  3. Facilities for diagnosis and treatment should be available.
  4. There should be a latent stage of the disease.
  5. There should be a test or examination for the condition.
  6. The test should be acceptable to the population.
  7. The natural history of the disease should be adequately understood.
  8. There should be an agreed policy on whom to treat.
  9. The total cost of finding a case should be economically balanced in relation to medical expenditure as a whole.
  10. Case-finding should be a continuous process, not just a "once and for all" project.

In 2008, with the emergence of new genomic technologies, the WHO synthesised and modified these with the new understanding as follows:

Synthesis of emerging screening criteria proposed over the past 40 years

  • The screening programme should respond to a recognized need.
  • The objectives of screening should be defined at the outset.
  • There should be a defined target population.
  • There should be scientific evidence of screening programme effectiveness.
  • The programme should integrate education, testing, clinical services and programme management.
  • There should be quality assurance, with mechanisms to minimize potential risks of screening.
  • The programme should ensure informed consent, confidentiality and respect for personal, bodily autonomy.
  • The programme should promote equity and access to screening for the entire target population.
  • Programme evaluation should be planned from the outset.
  • The overall benefits of screening should outweigh the harm.

In summation, "when it comes to the allocation of scarce resources, economic considerations must be considered alongside 'notions of justice, equity, personal freedom, political feasibility, and the constraints of current law'."[11]

Types

  • Mass screening (sometimes termed population-based screening): The screening of a whole population or subgroup. It is offered to all, irrespective of the risk status of the individual.
  • High risk or targeted screening or selective screening: High risk screening is conducted only among high-risk people.
  • Multiphasic screening: The application of two or more screening tests to a large population at one time, instead of carrying out separate screening tests for single diseases.
  • When done thoughtfully and based on research, identification of risk factors can be a strategy for medical screening.[12]

Examples

Common programs

In many countries there are population-based screening programmes. In some countries, such as the UK, policy is made nationally and programmes are delivered nationwide to uniform quality standards. Common screening programmes include:[citation needed]

  • Cancer screening
    • Pap smear or liquid-based cytology to detect potentially precancerous lesions and prevent cervical cancer
    • Mammography to detect breast cancer
    • Colonoscopy and fecal occult blood test to detect colorectal cancer
    • Dermatological check to detect melanoma
    • PSA to detect prostate cancer
  • PPD test to screen for exposure to tuberculosis
  • Beck Depression Inventory to screen for depression
  • SPAI-B, the Liebowitz Social Anxiety Scale and Social Phobia Inventory to screen for social anxiety disorder
  • Alpha-fetoprotein, blood tests and ultrasound scans for pregnant women to detect fetal abnormalities
  • Bitewing radiographs to screen for interproximal dental caries
  • Ophthalmoscopy or digital photography and image grading for diabetic retinopathy
  • Ultrasound scan for abdominal aortic aneurysm
  • SARI Screening Tool for COVID-19 and MERS[13]
  • Screening of potential sperm bank donors
  • Screening for metabolic syndrome
  • Screening for potential hearing loss in newborns
  • Hearing screening at occupational health programs[14]

School-based

Most public school systems in the United States screen students periodically for hearing and vision deficiencies and dental problems. Screening for spinal and posture issues such as scoliosis is sometimes carried out, but is controversial as scoliosis (unlike vision or dental issues) is found in only a very small segment of the general population and because students must remove their shirts for screening. Many states no longer mandate scoliosis screenings, or allow them to be waived with parental notification. There are currently bills being introduced in various U.S. states to mandate mental health screenings for students attending public schools in hopes to prevent self-harm as well as the harming of peers. Those proposing these bills hope to diagnose and treat mental illnesses such as depression and anxiety. [citation needed]

Screening for social determinants of health

The social determinants of health are the economic and social conditions that influence individual and group differences in health status.[15] Those conditions may have adverse effects on their health and well-being. To mitigate those adverse effects, certain health policies like the United States Affordable Care Act (2010) gave increased traction to preventive programs, such as those that routinely screen for social determinants of health.[16] Screening is believed to a valuable tool in identifying patients' basic needs in a social determinants of health framework so that they can be better served.[17][18]