Screening Dr Gerry Bryant

What is screening? Systematic application of a test or enquiry, to identify individuals at sufficient risk of a specific disorder to benefit from further investigation or direct preventive action, among persons who have not sought medical attention on account of symptoms of that disorder Sieving, sorting, treating

Why screen? Protection of public health Prior to entering an organisation Protection of the workforce For life insurance Early diagnosis of disease

Some screening programmes can help All screening programmes can harm

Pros & cons of screening

Testing a screening programme - Wilson & Junger Criteria (1968) 1The condition being screened for should be an important health problem 2The natural history of the condition should be well understood 3There should be a detectable early stage 4Treatment at an early stage should be of more benefit than at a later stage 5A suitable test should be devised for the early stage 6The test should be acceptable 7Intervals for repeating the test should be determined 8Adequate health service provision should be made for the extra clinical workload resulting from screening 9The risks, both physical and psychological, should be less than the benefits 10The costs should be balanced against the benefits

Testing a screening programme - UK National Screening Committee criteria (2003) The condition 1The condition should be an important health problem. 2The epidemiology and natural history of the condition, including development from latent to declared disease, should be adequately understood and there should be a detectable risk factor, disease marker, latent period or early symptomatic stage. 3All the cost-effective primary prevention interventions should have been implemented as far as practicable. 4If the carriers of a mutation are identified as a result of screening the natural history of people with this status should be understood, including the psychological implications.

Testing a screening programme - UK National Screening Committee criteria (2003) The test 5There should be a simple, safe, precise and validated screening test. 6The distribution of test values in the target population should be known and a suitable cut-off level defined and agreed. 7The test should be acceptable to the population. 8There should be an agreed policy on the further diagnostic investigation of individuals with a positive test result and on the choices available to those individuals. 9If the test is for mutations the criteria used to select the subset of mutations to be covered by screening, if all possible mutations are not being tested for, should be clearly set out.

Testing a screening programme - UK National Screening Committee criteria (2003) The treatment 10.There should be an effective treatment or intervention for patients identified through early detection, with evidence of early treatment leading to better outcomes than late treatment. 11.There should be agreed evidence-based policies covering which individuals should be offered treatment and the appropriate treatment to be offered. 12.Clinical management of the condition and patient outcomes should be optimised in all healthcare providers prior to participation in a screening programme.

Testing a screening programme - UK National Screening Committee criteria (2003) The screening programme 13There should be evidence from high-quality randomised controlled trials that the screening programme is effective in reducing mortality or morbidity. Where screening is aimed solely at providing information to allow the person being screened to make an 'informed choice' (for example, Down's syndrome and cystic fibrosis carrier screening), there must be evidence from high-quality trials that the test accurately measures risk. 14The information that is provided about the test and its outcome must be of value and readily understood by the individual being screened. 15There should be evidence that the complete screening programme (test, diagnostic procedures, treatment/intervention) is clinically, socially. and ethically acceptable to health professionals and the public. 16The benefit from the screening programme should outweigh the physical and psychological harm (caused by the test, diagnostic procedures and treatment).The opportunity cost of the screening programme (including testing, diagnosis and treatment, administration, training and quality assurance) should be economically balanced in relation to expenditure on medical care as a whole (ie value for money). 17There should be a plan for managing and monitoring the screening programme and an agreed set of quality assurance standards. 18Adequate staffing and facilities for testing, diagnosis, treatment, and programme management should be available prior to the commencement of the screening programme. 19All other options for managing the condition should have been considered (for example, improving treatment and providing other services), to ensure that no more cost-effective intervention could be introduced or current interventions increased within the resources available. 20Evidence-based information, explaining the consequences of testing, investigation, and treatment, should be made available to potential participants to assist them in making an informed choice. 21Public pressure for widening the eligibility criteria for reducing the screening interval, and for increasing the sensitivity of the testing process, should be anticipated. Decisions about these parameters should be scientifically justifiable to the public. 22If screening is for a mutation, the programme should be acceptable to people identified as carriers and to other family members.

11 Randomised control trials of screening time randomise screenno screen outcome treat early disease treat at time of presentation screen no disease or risk factor identified early disease or risk factor identified outcome randomise treat early disease treat at usual time of presentation outcome

12 Bias in screening programmes Lead time bias biologic onset of disease disease detectable by screen Woman A diagnosed at screen Symptoms develop - Woman B diagnosed Woman A & B die of disease 3 year survival 5 year survival Length time bias over-representation among screen-detected cases of those with long pre-clinical phase of disease - less rapidly progressive

13 Mathematics of screening

14 Sensitivity and specificity Sensitivity = a/(a+c) if you have the disease, probability of testing positive (want to be high) Specificity = d/(b+d) if you do not have the disease, probability of testing negative (want to be high)

15 Predictive values Positive predictive value = a/(a+b) probability that a person with a positive test has the disease Negative predictive value = d/(c+d) probability that a person with a negative test does not have the disease

NHS Cancer Screening Programmes - Breast Screening (1988) To detect cancer or DCIS Who? – women aged years by invite, >70 by self-referral What? – mammography How often? – every 3 years Recent changes? – extend to years from 2012 Cost? – £75m per year in England – £37.50 for each woman invited – £45.50 for each woman screened Does it work? – 500 women screened – 1 breast cancer death prevented Who does what? – PCT – Primary Care Team – Breast Screening Unit – Breast Surgery

NHS Cancer Screening Programmes - Cervical Cancer Screening (1988) To detect pre-cancerous changes - CIN Who? – women aged 25 to 65 years What? – liquid-based cytology of cells from cervical sweep How often? – women aged 25 to 50 every 3 years – women aged 50 to 65 every 5 years Cost? – £157m per year in England Does it work? – estimated prevents 3900 cervical cancers per year in England Who does what? – PCT – Primary Care Team – Laboratory – Colposcopy Service Failsafe systems – Laboratory – Colposcopy Service

NHS Cancer Screening Programmes - Bowel Cancer Screening (2006) To detect cancer (and pre-malignant polyps) Who? – people aged years – self-referral of older people by telephoning What? – FOB kits – by post How often? – every two years Recent changes? – roll-out to age from this year Cost? – £76.2m per year in England Does it work? – 1000 screened - 2 bowel cancers detected – 16% reduction in bowel cancer deaths Who does what? – Programme Hub (Eastern) – Screening Centre (Derby) – Cancer Centre (Derby-Burton) – Primary Care

NHS Screening Programmes - Diabetic Retinopathy Screening (2007) Who? – aged over 12 years with diabetes mellitus What? – digital retinal photography How often? – annual Who does what? – PCT – Primary Care – Retinopathy Screeners – Ophthalmologist

NHS Screening Programmes - Abdominal Aortic Aneurysm Screening (2013) Who? – 65 year old men by invitation – men > 65 years who have never been screened or treated for AAA by self- referral – not yet available here - roll-out by 2013 (Leicestershire & South Staffs already included) What? – USS of abdomen – diameter of aorta measured How often? – once Will it work? – affects 1 in 25 men aged – screening may reduce death from ruptured AAA by 50% Who does what? – Local Screening Centre – Vascular Surgery Service – Primary Care

Others Prostate cancer – men – PSA test Chlamydia – sexually active under 25’s – urine test - postal Health check – vascular risk assessment – not yet rolled out ?2013 – adults over age 40 years – every 5 years – to assess / reduce / manage risk of stroke, heart disease, kidney disease & diabetes – age, gender, ethnicity, lifestyle, smoking, family history, BMI, BP, cholesterol – blood glucose +/- U&Es if indicated

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