1. Uses and Abuses of Screening Tests Screening tests are ubiquitous in practice Principles of screening are widely misunderstood Goal of screening is to test apparently well people to find those at increased risk of a disease or disorder Inappropriate screening is harmful –Injurious to one’s health – Stigmatizing –Costly

2. Differences between Clinical and Screening Tests Clinical Tests Patient Initiated Patient with a complaint Risk and cost acceptable to the patient Screening Tests Provider Initiated Healthy patient Patient not seeking help If patient initiated, then can be costly and of no clinical value

3. When Earlier Diagnosis is Worth the Cost If improves survival or quality of life If the clinician has the time to manage the Dx before Sx develop If the patient with an earlier Dx will comply with intervention If the screening program effectiveness has been established If the test cost, accuracy and acceptibility are acceptable to the patient and society (Sackett, Clinical Epidemiology: a basic science for clinical medicine)

4. Questions Clinicians Should Ask Themselves Before Screening a Patient What are the potential harms of screening? What right do clinicians have to rob people of their perceived health, and for what gain? If a test is available, should it be used? Is the test valid? Where should the cut-off for abnormal be? Can test results be trusted? Should a follow-up test be done? Does the screening test really improve health? (Grimes, Lancet 2002)

5. Criteria Needed for a Screening Program Disease –medically important and clearly defined –prevalence known –effective intervention exists Policy –cost-effective –facilities for Dx and Rx available –course of action is generally agreed upon and acceptable Tests –safe, valid, and reliable –reasonable cut-off level defined (Cuckle, Principles of screening. In: Antenatal and neonatal screening)