Concepts of Screening

1. Concepts of Screening Helena Kemp Consultant Chemical Pathologist North Bristol NHS Trust

2. Outline of talk • The definition & principles of screening • National screening policy • The screening ‘test’ • The screening ‘programme’ • Quality management • Public & professional education • A model of screening - MCADD • The balance of harm vs benefit

3. Definition of Screening ‘The systematic application of a test or enquiry to identify individuals at risk of a specific disorder to warrant further investigation or direct preventative action, amongst persons who have not sought medical attention on account of symptoms of that disorder. ‘

4. Principles of ScreeningWilson and Jungner 1968 • The condition is an important health problem • Its natural history is well understood • It is recognisable at an early stage • Treatment is better at an early stage • A suitable test exists • An acceptable test exists • Adequate facilities exist to cope with abnormalities detected • Screening is done at repeated intervals when the onset is insidious • The chance of harm is less than the chance of benefit • The cost is balanced against benefit

5. Screening in the UK Improving Screening: A Public Health Task for the Nineties Public Health Network – March 1994 - Variations in policy, including no policy - Variations in practice - Absence of standards - Absence of performance measurement - Patchy training - Poor patient information - No clear lines of accountability

6. The UK National Screening Committee • Established 1996 • The UK National Screening Committee advises Ministers, the devolved National Assemblies and the Scottish Parliament on: • The case for implementing new population screening programmes. • Screening technologies • The case for continuing, modifying or withdrawing existing population screening programmes • Set up practical mechanisms to oversee the introduction & implementation of a new programme in the NHS & monitor effectiveness and quality assurance

7. Consumer groups HTA Population ScreeningPanel Advisory groups egg Child Health Subgroup and antenatal Subgroup DH Policy Research Programme NSC Royal Colleges Other sources of evidence e.g. MRC Professional organisations NHS managing clinical innovations group

8. Revised definition of screening ‘Screening is a public health service in which members of a defined population, who do not necessarily perceive they are at risk of, or are already affected by a disease or its complications, are asked a question or offered a test, to identify those individuals who are more likely to be helped than harmed by further tests or treatment to reduce the risk of a disease or its complications’.

9. UK National Screening Committee revised criteria 2003www.nsc.nhs.uk/pdfs/criteria.pdf • Appraise the viability, effectiveness and appropriateness of a screening test • Additional criteria: • Requirements of screening programmes which include mutation analysis • Evidence base i.e. Randomised Controlled Trial data to indicate that screening programme effectively reduces mortality or morbidity • Quality management of screening programmes • Provision of information for informed choice to participate

10. NSC screening policieswww.nsc.co.uk • Nationally managed programme • e.g. Antenatal Downs screening, Newborn CF, Breast Cancer • Planned National programme • e.g National Chlamydia Screening Programme • Screening - with reservations • e.g. Prostate Cancer (Prostate Cancer Risk Management Programme) • Under review • e.g. abdominal aortic aneurysm men over 65 years • Not recommended • e.g. antenatal CF, CAH, bladder cancer

11. UK National Screening Committee Programmes Director, Sir Muir Gray Vascular Screening Cancer Screening Programmes Fetal, Maternal & Child Health subgroup (FMCH) Vascular Diseases Risk Management Diabetic Retinopathy Sickle Cell and Thalassaemia Screening Down‘s Syndrome Screening Fetal Anomaly Ultrasound screening Infectious Diseases; HIV, Hepatitis B, Syphilis, Rubella Newborn Blood spot screening Cystic Fibrosis screening Newborn and 6-8 week Infant Physical Examinations Newborn Hearing Screening Cervical Screening Breast Screening Bowel Cancer Screening NSC Organisational Structure

12. The screening test • An enquiry e.g. ethnicity • An examination e.g. 6-8 wk physical examination • An investigative procedure e.g. fetal anomaly scanning • A single analytical test e.g. phenylalanine PKU • Multiple markers • Multivariate risk calculation • Multi protocol

13. Screening Algorithm newborn CF screening

14. Assessing the performance of a screening test Sensitivity = a / a + c Specificity = d/ b + d Positive predictive value = a/ a + b Negative predictive value = d/ c + d

15. Performance of a screening test • Detection rate (sensitivity) The proportion of affected individuals with a positive result • False positive rate (specificity = 1-FPR) The proportion of unaffected individuals with a positive result • Positive predictive value The chance that those with a positive test result are affected • Performance will depend on cut-off levels chosen • Cut–off chosen will be influenced by many factors including justification for further tests and resources

16. Roc curve analysis

17. Screening programmes • Systematic • Breast cancer, newborn bloodspot • Opportunistic • STI • Targeted • Tay sachs ashkenasi jewish population

18. Newborn bloodspot screening Pre-analytical Obtaining informed consent Child, family, midwife Taking the sample Midwife Sending sample to lab Midwife Analytical Primary screening test Screening lab Second tier tests Screening & referral labs Interpretation and reporting Screening lab consultant Post analytical Checking coverage Child Health Department Reporting normal results to parents Health visitor Confirmation of positives Specialist paediatrician Genetic counselling Genetic Nurse/midwife

19. Integration of screening programmes

20. Principles of quality management for screeningNuffield Institute of Health March 2000 • A clear coherent framework of objectives, standards & guidance • A culture of learning, not blame • A partnership with staff and users • Continuous quality improvement • Clear management structures • Effective & efficient performance measurement • Adequate systems & resources • Bridging the expectation gap

21. Set process standards coverage, timeliness, communication of results, referral standards Information for parents and professionals PatientRegisters Training UKNSPC Policy for blood spots retention Policy for parental consent Informatics The UK Newborn Screening Programme Centre (est. 2002)

22. Timely sample collection Timely sample dispatch Completeness of coverage Enhanced tracking abilities Timely notification of unscreened babies Timely processing of positive screening samples Process standards Newborn bloodspot screening

23. Laboratory quality standards newborn sickle cell screening • Accreditation by an appropriate body (e.g. CPA). • Consultant led service with defined lines of responsibility for all laboratory aspects of the service. • HPLC & IEF methodology with a different technique for confirmation from initial screen. • Appropriate internal quality control undertaken and documented • Compulsory participation in an accredited EQA appropriate for newborn screening (NEQAS scheme) • Provision of information on screening performance to monitoring groups (NSC, NPC). • Workload should exceed 25,000 specimens per year (ideally 50,000).

24. Parent Information

25. Education resources for HCP • Internet resources • www.screening.nhs.uk/cpd • Programme specific training material • Educational programs • PEGASUS • NSC commissioned professional training for informed choice • Other Resources • Cards for Midwives

27. A model of screening -MCADD • Evidence base • Pilot study • Assessment against NSC criteria • Ministerial announcement Feb 2007 • Implementation

28. The balance of harm vs benefit

29. Extended newborn screeningNewborn Screening with Tandem MS - New South Wales, Australia B Wilcken et al NEJM 2003; 348:2304-12 • 4 years experience 1998-2002 • 362,000 newborns screened • 31 disorders detected, 57 babies (15.7 per 100,000 screened) • Urea cycle 7 • Amino acid disorders 9 • Organic acid disorders 12 • Fatty acid oxidation disorders 29 • SCAD 5 • MCAD 17 • VLCAD 3 • Carnitine defects 4

30. Effect of Expanded Newborn screening for biochemical genetic disorders on child outcomes and parental stressWaisbren et al JAMA 2003 290 2564-2572 • Prospective study of expanded screening 1999-2002 • Participants • 50 affected families – identified by NS • 33 affected families - clinically diagnosed • 94 false positive children • 81 screen normal children • Main outcome measures • Child’s health and development • Parental Stress index

31. Results • Cases identified by newborn screening vs clinical diagnosis • 28% NS vs 55% clinically identified required hospitalisation • 1 NS vs 8 clinically identified children severe learning difficulties • Mothers in screened group reported lower stress on PSI than mothers in clinically identified group • False positive group vs normal screening result • 21% children with false positive results vs 10% hospitalised • Mothers in false positive group attained higher scores on PSI • Mothers in false positive group attained higher scores on Parent child dysfunction subscale

32. False positives in expanded newborn screening • Prevalence of true positives • 1 in 2400 infants screened (0.04%) • Prevalence of false positives • 1 in 300 infants screened (0.33%) • 8 false positives for every true positive • Approx 13,000 false positives/year A review of the psychosocial effects of false positive results on parents and current communication practices in newborn screening Hewlett & Waisbren JIMD 2006 29:677-682

33. Useful resources • www.nelh.nhs.uk/screening • www.nsc.nhs.uk • www.screening.nhs.uk • Downs screening • www.nehl.nhs.uk/screening/dssp/home.htm • Newborn screening • www.newbornscreening-bloodspot.org.uk • Sickle cell and thalassaemia • www.kcl-phs.org.uk/haemscreening