Criteria on whether screening for a disease is worthwhile.1
The burden of disease must be sufficient.
Screen only for conditions that cause severe disease, disability, or death.
Consider prevalence of target disease and ability to identify high-risk group, since the yield of screening is higher in high-risk groups.
Point 3shared decision-making may be important when the benefit-to-harm ratio is uncertain.
Point 4: Screening tests and preventive interventions can have benefits and harms. Adverse outcomes can include side effects, false-positive results, overdiagnosis, anxiety, and radiation exposure. The cost-effectiveness of strategies is evaluated based on the cost per year of life saved.
Point 5: The decision to implement a population-based screening and prevention strategy requires weighing the benefits and harms, including the economic impact of the strategy. The costs include not only the expense of the intervention but also time away from work, downstream costs from false-positive results, “incidentalomas” or adverse events, and other potential harms.
The test used for screening must be of high quality.
Screening tests should accurately detect the target disease when it is asymptomatic.
Screening tests should have high sensitivity and specificity.
Test results should be reproducible in a variety of settings.
Screening tests must be safe and acceptable to patients.
Ideally, screening tests should be simple and shown to be cost effective.
There must be effective treatment for the target disease.
Early detection followed by treatment must improve survival compared with detection and treatment at the usual time of presentation; in other words, people in whom the condition was diagnosed by screening should have better health outcomes than those in whom the condition was diagnosed clinically.
The benefits of screening must outweigh any adverse effects of the screening test, treatment, or impact of early diagnosis.
Ideally, benefits and harms are evaluated through a randomized trial of screening.
The best outcome to measure is either all-cause mortality or disease-specific mortality, such as breast cancer or prostate cancer mortality.
Outcomes such as cancer stage distribution (ie, whether there are more or fewer early-stage cancers found) and length of survival after diagnosis can be misleading because of lead time and length time biases.
Lead time bias: If early treatment is not more effective than later treatment, the duration of time the individual lives with the disease is longer, but the mortality rate is the same.
Length time bias: Cancers that progress rapidly from onset to symptoms are less likely to be detected by screening than slow-growing cancers, so that screening tends to identify a group with a better prognosis.
References
1. Altkorn D, Schulwolf E. How do I determine which screening tests to order?. In: Stern SC, Cifu AS, Altkorn D. eds. Symptom to Diagnosis: An Evidence-Based Guide, 4e. McGraw-Hill Education; 2020. Accessed October 12, 2024. https://accessmedicine.mhmedical.com/content.aspx?bookid=2715§ionid=249057720