Disease Screening: Early Detection and Prevention

• Screening involves testing healthy individuals for early stages or precursors of a disease, without existing symptoms related to that disease.
• A well-functioning screening program identifies earlier stages of a disease than clinical or general practice diagnoses.
• Sensitivity indicates how well a test identifies those with a (preclinical stage of a) disease.
• Specificity indicates how well a test correctly identifies those without a (preclinical stage of a) disease, avoiding unnecessary further tests.
• Optimum between referring or not referring screened individuals depending on the relative severity of a false-positive test result in comparison to a false-negative test.
• Overdiagnosis and overtreatment involves early detection and treatment of a disease through screening that would never have caused symptoms (or diagnosis) during a patient's lifetime; this is one of the main drawbacks of screening.

Theories and Methods

• The natural course of a disease, screening test characteristics, and treatment options at an early stage determine expected health benefits for a population or group of patients.
• Large-scale randomized trials with participants who undergo the screening test vs. those who do not, provides evidence of how much health gain early detection and treatment can achieve.
• The difference between numbers and stages of diseases in population research vs. diagnosed diseases in the clinic gives a good indication of the advancement and the preclinically detectable stage.
• The benefit-risk ratio is the relationship between health benefits and side effects of a screening program and must be favorable enough to consider screening and have a reasonable relationship between costs and effectiveness.

Felten

• Large-scale trials in breast cancer, prostate cancer, colon cancer, and lung cancer show that screening can detect the disease at an earlier stage and reduce mortality.
• For many of Dutch population studies on cancer, the specificity is more than 90%, while sensitivity usually varies between 60 and 90%.
• Three cancer screening programs are implemented in the Netherlands and many European countries: cervical cancer, breast cancer, and colon cancer.
• The United States Preventive Services Task Force (USPSTF) provides recommendations on screening for many diseases that have a favorable benefit-risk ratio.
• The assessment of benefit-risk ratio is often sensitive, and this consideration of pros and cons at the individual and population level can vary.

Introduction

• Primary prevention aims to prevent the development of a disease.
• Secondary prevention, or screening, is aimed at detecting conditions in an early stage, so that early treatment is possible and deterioration of the disease can be prevented.
• Screening and systematic early detection of disease are nearly the same.

Key concept

• Screening involves testing healthy individuals for precursors or early stages of a disease without existing symptoms.
• A well-functioning screening program identifies earlier disease stages than clinical practice.

Theory of screening: general principals

• Screening is widely practiced in primary care and hospitals, though not always explicitly.
• Many doctors aim recognize diseases as early as possible.
• Diagnosis includes measuring blood pressure, blood glucose, or prostate-specific antigen (PSA) to detect hypertension, diabetes, and prostate cancer.
• A screening test separates individuals to be examined further from those who do not for example, test-positives and test-negatives.
• Screening means literally 'to sift'.
• The screened group with a high risk will turn out to have the disease without symptoms with further diagnostics; treatment will hopefully be more effective than later.

Structured programs

• Population screening involves actively offering it to large groups of general population.
• The Dutch Population Screening Act (Wbo) protects people against population studies harmful to their physical and mental health.
• Screening using ionizing radiation, cancer screening, and screening for severe diseases without prevention are licensed in the Netherlands; the Minister of Health, Welfare and Sport can grant licenses on the Health Council's recommendation.

Theory of screening

• An underlying principle says a disease is detectable with a test during a period before clinical diagnosis and this is precinical detectable stage.
• The duration depends on the disease and the test, influenced by age or gender.
• A more sensitive test can detect disease at an earlier stage.
• The extent of diagnosis advancement done by screening determined by screening test's effectiveness and the disease itself because rapid-growing tumors may not be easily detected.
• The potential health gain of early detection and treatment depends on the disease's course and therapeutic possibilities.

Spectrum of diseases

• On one hand, pancreatic cancer
• On the other hand, prostate cancer or cervical cancer
• These diseases may be detected up to ten years before clinical diagnosis.
• The number and stages of diseases found via population screening gives a good indication of advancement.
• Large-scale randomized trials can provide evidence for how much health gain early detection and treatment can achieve.

Screening test and qualities

• Many factors decide decision-making between policymakers considering mass screening and individuals considering invitations.

Screening Test and Disease Relationship

• The primary question is the ability of the screening test to differentiate between individuals likely to have the disease and those who are not.
• The quality relies on reliability and validity- repeatability and agreement across assessors. Validity indicates to what extent the test can detect a certain disease.
• Validity relates to the sensitivity, specificity, and predictive values of the test.

Test characteristics

• Sensitivity and specificity determine each tests ability to identify a disease.
• Tradeoff needs to be considered to the severity of having a false-positive and false-negative.

Screen result and accuracy

• Choosing a good cut-off point between a positive and negative test is important.

• Radiologists must determine what qualifies as a positive result of a mammogram and values might vary differently among various radiologists who each value 1% chance of finding cancer.

• Different tests have different degrees of sensitivities and specificities.

• The higher PSA value as the cut-off point, the lower the sensitivity but the higher the specificity. and vice versa.

• Reviewing all possible cut-off points and plotting them with the given sensitivity and specificity in a figure, receiver operating characteristic curve- ROC, make choosing combination easier shown from x-rays with the use of systems or trained radiologists.

• The lower the cut-off point, the higher the sensitivity but lower the specificity. This relies on several factors like comparing severity.

• Sensitivity of the test usually can't directly be determined because it would need to be required for all negative personnel to be tested.

Benefits/drawbacks of screening

• Criteria of good decision is determining if the proper balance is being assessed for positives/negatives of the persons involved.
• If tests do contain errors it can be a set back given its inaccuracy.

In-depth Overdiagnostics/Treatments

• Screening is an effective mode of action provided it's an effective test.
• Screening for cancer is most important because it often leads to a false result.
• Testing positive can cause issues when the person doesn't test right/ have cancer.
• A very useful program would allow for early detection and less side effects.
• Other programs can increase other diseases as well.
• Proper screening tests help determine diagnosis and risks.

Benefits of screening

• Less unfavorable outcomes with gains in health.
• Efficient Diagnostics
• Reduced or mutilating treatments

Cons of screening

• Over-diagnostics and treatment
• Side effects
• False rest assured and unchecked issues later on

Screening for Cancer

• Screening is a valuable tool for treating cancer.
• There can be negative side effects, but with the proper evaluation can change the situation.

Overdiagnostics and treatment

• Early diagnoses can bring forth underlying diseases as well.
• Many early detections would not have come to light had it not gotten screened and often not worth worrying about.

Screening considerations.

• Good screening should be beneficial for society.

• Test should be accepted and provide the proper capacities.

• Balance should exist from wins and what is provided.

• Benefits, losses, diagnostic advances.

• Overall, effect of screening on an individual should be considered/ reviewed.

• The course of disease, test, and when discovered can determine better health.

• Tests should be implemented to accurately create the appropriate screening.

• Implementations must not further negatively affect social economic groups/effects.

• Screening to have appropriate and equal balance.

• Screening most accurate and helps the population.

• The most valuable information is from over/mis-diagnostics.

• What must be considered is if tests can be performed, what conditions and test could be.

• USPSTF states screening has many accurate and helpful test benefits if used appropriately.

• Weighing benefits vs individual/community is beneficial.

• Certainty of the outcomes matters and creates good habits.

• What are the negative side effects? Benefits? Is this truly worth the time?

• The test gives a moment to asses, and must be accurate.

• Balance is required for safety tests and effectiveness for the people.

• There is more likelihood they will die and have the chance to die without knowing.

• Does the criteria meet the standards. - Cancer specific.

• What happens with an abnormal situation occurs.

Risks of certain practices

• Risk stratifications - Women with low risk, women with high.

• Case study - Screen/assess.

• Screening is great however must be considered.

• Screening done with the aid from long term smokers/ex - reduces the damage effects from cancer.

• One should note, that these criteria are more or just as important as ever.