Introduction
Population-based screening is a medical screening examination offered systematically to all persons in a defined target group within a program governed by approved policies, procedures, quality management, monitoring, measurement, and evaluation. Population-based screening is a well-organized, integrated approach in which all activities along the screening pathway are planned, coordinated, monitored, and assessed through a quality-improvement framework. All of these activities must be sufficiently funded to ensure that the benefits are maximized.
The Population Cancer Screening Program is supported by the values of access and equality, which are essential principles of population-screening programs, and is designed to provide guidance and inform decision-making.
Background Of Population Cancer Screening:
Population-based cancer-screening programs detect early symptoms of disease or signs that a person has a high probability of developing the disease. In many cases, early identification of cancer increases the possibility of effective treatment.
It is essential to remember that a screening test does not definitively diagnose cancer at the initial stage of testing. Further medical examinations are needed to confirm the results of a screening test, establish a diagnosis, and begin treatment in the early stage of the disease.
Screening Process
The World Health Organization (WHO) defines screening as the presumptive identification of unrecognized disease or defects through medical examinations, tests, and other measurements that can be applied rapidly. Screening is intended for everyone in a defined target population who does not have symptoms of the disease or disorder being screened for. The procedure can identify:
- A pre-disease abnormality
- early disease
- Disease risk indicators
The goal of screening for an illness or a risk indicator is to decrease the burden of disease in the community and lower the rates of disease, morbidity, and death. This is achieved by intervening to reduce an individual’s risk of disease or by detecting the disease earlier, on average, than would normally occur without screening, thereby improving disease outcomes.
Screening can decrease the risk of developing or dying from a disease, but it does not guarantee that the disease will not occur or, if it occurs, that it can be treated. A positive screening examination identifies people who have a greater probability of having the disorder and who require additional medical examinations to determine whether they have the disease or condition (Services, n.d.).
The following diagram presents the policy-analysis triangle that describes the screening pathway. Underlying the pathway is the principle of quality assurance at each point.
Because screening has benefits, costs, and harms, there is an ethical duty to maximize benefits and minimize harm, and the overall benefits should outweigh any harms that could result from screening. When community resources are used to fund screening, there should be community agreement that the benefits of screening justify the cost of testing.
Benefits Include:
- Reducing the burden of disease on the community and individuals
- Reducing mortality from the disease
- Reducing morbidity from the disease
- Improving disease outcomes
Damages Related To Population Cancer Screening May Include:
False positives: when the screening examination and assessment produce a positive result, but the person does not have the disease.
False negatives: when a screening examination and assessment produce a negative result, but the person does have the disease.
Overdiagnosis is a term used to describe some cancers and conditions that are detected and treated but might never have become dangerous during an individual’s lifetime. It does not refer to an error.
Other physical and psychological harms: harms that might occur as a consequence of screening or treatment.
Developing A Cancer Screening Test
Population-screening programs are offered only when a range of conditions can be met. These conditions may include:
- The cancer has a high degree of mortality (death) and morbidity (illness) in the population.
- The test can identify the disease or condition in its early stages or detect signs that the disease may develop in the future. These tests can be used as a warning that cancer may develop.
- The disease or illness can be treated if identified at an early stage, and treatment is more effective, affordable, safe, or acceptable in the early stages. The likelihood of successful treatment is higher when the disease is detected early.
- The screening test is acceptable to most people because people may avoid unpleasant or painful medical examinations, particularly if they have no symptoms.
- The program, including treatment when required, must be accessible to the majority of individuals in the target population. If the program is not accessible, it will be difficult to identify cancer in its early stages.
- The target population can be contacted through registers maintained in a central registry to undergo screening. People who have a higher risk of developing the disease can be invited for medical examinations at specified intervals, for example, by sending them an email.
- The program is cost-effective.
These strict requirements mean that population-based cancer-screening programs currently exist for only three types of cancer: cervical, breast, and bowel cancer. However, medical researchers are developing and testing screening methods for additional types of cancer. New tests could become available in the future.
Population-Based Cancer Screening:
Many population-based cancer-screening programs operate worldwide. Three of them are explained below:
Breast Screening Program: This program aims to identify early signs and stages of breast cancer in women aged 50–69. The screening test used is a mammogram (X-ray) of the breasts every two years. This program operates in many countries and has successfully identified cancer in its early stages and saved many lives.
Cervical Screening Program: This program aims to detect changes in the cervix that may lead to cervical cancer in women. The screening test used for medical examination is a Pap test, in which a small sample of cervical cells is obtained. Women are encouraged to begin Pap tests at 18 years of age and continue them thereafter.
Bowel Cancer Screening Program: This program aims to check for early signs of bowel cancer. It currently invites people aged 50 to 65 years to undergo screening. The screening test used is a fecal occult blood test (FOBT), which can be completed in the participant’s own home and detects traces of blood in a stool sample.
Analysis Of Success
To expand awareness and access to care, a coordinated approach must be established that includes empowerment and engagement related to integrated, person-centered services at all stages of care. This includes improving health literacy and decreasing cancer stigma. Building diagnostic capacity and improving referral pathways can overcome common barriers to timely diagnosis. Healthcare facilities at all levels of care must be equipped with the capacity to recognize cancer signs and perform or refer patients for diagnostic examinations. Pathology is particularly important in cancer diagnosis.
The Population-Based Cancer Screening Program framework was established to inform decision-makers of the significant issues that should be considered when assessing prospective programs around the world. The framework is categorized into two parts:
- The principles that must be used to examine whether cancer screening should be offered or a screening program should be introduced for particular cancers or conditions.
- The important principles for the operation and supervision of cancer-screening programs.
Decision-making relies on several factors, including the cancer being targeted, the risk of that particular cancer in a specific population, and the capacity and resources of the health system in a given country. In areas where most patients are diagnosed at a late stage, early diagnosis could have a significant influence and can help build better health-system capacity. If recognition of cancer at an early stage is possible, it is vital that appropriate intervention at that time has the potential to change the course of the disease. Preferably, there should be strong evidence from well-conducted clinical trials that early treatment or intervention improves outcomes.
CPC can play a crucial role in cancer prevention and screening, but it is necessary to define and establish the role of this center. The goal is to achieve improved outcomes in the early detection of the most common malignant neoplasms.
Screening programs for cervical and colorectal cancers have higher success rates than others because these cancers are comparatively similar, slow-developing, and often have recognizable precursors that can be detected and removed. However, identifying the true obligate precursors of invasive disease remains a challenge worldwide.
Challenges Of Cancer Screening Programs
Cancer screening has significantly decreased illness and death rates around the world. For example, after the establishment of the National Cervical Screening Program in 1992, the death rate from cervical cancer almost halved and is now among the lowest in the world. This reduction in cervical cancer was associated with the population-screening program.
- Despite the importance of screening, many challenges and difficulties need to be overcome when examining large numbers of individuals in a population-based program, including:
- Some people may find certain medical screening tests offensive, painful, unpleasant, or awkward and may not be willing to participate in the program.
- An individual may be frightened of medical examinations or procedures and avoid the screening process altogether. Anxieties or worries about a screening test should be discussed with a doctor. It may be useful to visit the doctor with a family member or colleague for support and comfort.
- Cancer-screening examinations are not perfect. Every test carries a small risk of producing a false negative. There is also a small risk of producing a false positive. This can result in unnecessary concern and invasive tests such as a biopsy. Some of these tests can carry a small but potentially significant risk of side effects or complications.
- Every test also carries a small risk of overdiagnosis, which refers to the diagnosis of a disease that would never cause symptoms or death during the individual’s lifetime.
Types Of Population Cancer Screening Programs
There are three methods for the detection of cancer:
Mass-based (population-based) screening: In this approach, all people in a defined age group are screened for cancer, and if cancer is identified, treatment is started promptly; an example is cervical-cancer screening.
Selective screening: In this method, specific groups of people in high-risk categories are screened. These people have a high risk of disease and may need a medical check-up every six months to one year. An example is genetic screening of individuals who have a strong family history of breast cancer.
Opportunistic screening: In this method, screening tests are offered to people who are being treated for other conditions but who have a higher probability of developing another disease. Screening may also be offered as part of a regular medical examination. An example is genetic screening offered to people with a known family history of breast, bowel, or skin cancer.
The Screening Test Policy
The screening examination must be sufficiently accurate to detect the condition before symptoms or other clinical indications appear. The result must have high accuracy, which is assessed by considering the sensitivity and specificity of the screening test. Accuracy is essential in a screening test. Sensitivity refers to the ability of an examination to correctly identify people who have the disease or condition; that is, the percentage of individuals with the disease at the time of screening who have a positive screening test.
Specificity describes the ability of the examination to correctly identify people who do not have the disease. A medical examination with poor specificity will result in a higher rate of false positives: healthy individuals will incorrectly test positive and may be subjected to more invasive diagnostic testing (McConnell, A. 2010).
Another valuable characteristic of a screening examination is the positive predictive value (PPV), which is the probability of having the disease if the screening test is positive (i.e., a true positive). PPV is influenced by the sensitivity and specificity of the medical examination and by how common or uncommon the condition is in the population being screened. In breast-cancer screening, for example, the PPV represents the total number of cancers identified as a percentage of women who are recalled for additional investigations after mammography screening (Buse & Walt, 2012).
The policy triangle demonstrates that several components drive health policy. Health policies are shaped by and contribute to their context, the use of power through influence or resources, and internal or external issues that may appear unrelated to the policy process itself.
Actors refers to individuals, organizations, or the state whose activities significantly affect health policy. All actors have their own interests and agendas. Examples of actors include individuals, international NGOs, national NGOs, pressure or interest groups, international organizations, bilateral agencies, funding organizations, private-sector companies, and the media.
Context refers to systemic factors that include administrative, financial, societal, or cultural factors at both national and international levels. These can influence health policy.
Content is the substance of a particular policy and details the issues and topics covered.
The process is the way in which policies are initiated, developed, framed, changed, communicated, implemented, and evaluated.
Lastly, the screening test should be acceptable to people and cause minimal anxiety; otherwise, participation in the screening program will be low. For example, some women find having a Pap test painful or uncomfortable and are therefore under-screened. Considerable resources are consequently required for educational campaigns to encourage women to undergo Pap tests. A smaller number of women have reported pain or anxiety during mammographic screening. Resources should be dedicated to radiographer training to address this issue.
Conclusion
Population cancer screening helps identify cancer in its earlier stages. Early detection of cancer usually increases the probability of successful treatment by identifying symptomatic patients as soon as possible. Delays in accessing cancer care are commonly associated with late-stage presentation, particularly in low-resource settings and vulnerable populations. The consequences of delayed or inaccessible cancer care include a lower probability of survival, greater morbidity from treatment, and higher costs of care, resulting in preventable deaths and disability from cancer. Early diagnosis can improve cancer outcomes by allowing treatment to begin at an early stage. It is therefore an important public-health strategy in all settings.
References
Services, D. of H. & H. (n.d.). Cancer screening. Retrieved August 23, 2017, from https://www.betterhealth.vic.gov.au:443/health/conditionsandtreatments/cancer-screening
Buse, K., Mays, N., & Walt, G. (2012). Making health policy. McGraw-Hill Education (UK).
McConnell, A. (2010). Policy success, policy failure and gray areas in-between. Journal of Public Policy, 30(3), 345-362.
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