2. Guided by, SUBMITTED BY, Dr.Mahmood Moothedath Ayshath Dr.Aseela,Dr Ashwathi Raifa.

3. CONTENTS Introduction Ice berg phenomenon of disease What is screening..?? Concept of screening.. Principles of screening Aims and objectives Screening V/S diagnostic tests Concept of lead time Population screening

4. When to screen.?? Screening requirements Uses of screening Types of screening Criteria for screening Screening test Problems of borderline Evaluation of screening programme Screening services Screening for oral cancer Trivandrum oral cancer screening study

5. INTRODUCTION Epidemiologist and others who study disease find that the pattern of disease in hospitals is quite different from that in a community.. That is, far larger population of disease (eg: diabetes, hypertension) is hidden from view in the community than is evident to physician or to the general public.. The anology of an iceberg, only the tip of which is seen, is widely used to describe the disease in the community…………

6. Iceberg Phenomenon of Disease The submerge portion of the iceberg represents the hidden mass of the disease (e.g. subclinical cases, carriers, undiagnosed cases). The floating tip represents what the physician sees in his practice.

7. The hidden part of the iceberg thus constitutes the mass of unrecognised disease in the community and its detection and control is a challenge to modern techniques in preventive medicine…..

8. WHAT IS SCREENING..?? Definition goes…………. The presumptive identification of unrecognised disease or defect by the application of tests, examinations or other procedures which can be applied rapidly to sort out apparently well persons who probably have a disease from those who probably do not….. (commission on chronic illness 1957 )

9. Screening is testing of apparently healthy populations to identify previously undiagnosed diseases or people at high risk of developing a disease… Screening aims to detect early disease before it becomes symptomatic…. Screening is an important aspect of prevention, but not all diseases are suitable for screening…

10. Key elements : Disease / disorder / defect Screening test Population

11. CONCEPT OF SCREENING The active search for disease among apparently healthy population is the fundamental aspect of prevention.. This is embodied in screening Historically, the annual health examinations were meant for the early detection of the “hidden “ disease. To bring such examinations within the reach of large masses of people with minimal expenditure of time

12. and money, a number of alternative approaches have come into use. They are based primarily on conserving the physician time for diagnosis and treatment and having technicians to administer simple, inexpensive laboratory tests and operate other measuring devices. This is the genesis of screening programme.. The original screening programmes were for individual diseases such as tuberculosis, syphilis or selected groups such as antenatal mothers, school children and occupational groups.

13. Over the years, the screening tests have steadily grown in number. Today screening is considered a preventive care function and some consider it a logical extension of health care..

14. Screening differs from periodic health examination in the following ways : 1) Capable of wide application 2) Relatively inexpensive 3) Requires little physician time

15. PRINCIPLES OF SCREENING Wilson and Jounger (1968) described 10 principles of screening.. 1)The condition should be an important health problem. 2)There should be an accepted treatments for person with recognised disease. 3)Facilities for diagnosis and treatment should be available. 4)There should be a recognisable latent or early symptomatic stage. 5)There should be a suitable test or examination.

16. 6)The test should be acceptable to the population. 7)The natural history of the disease,including its development from latent to declared disease, should be adequately understood. 8)There should be an agreed policy on whom to treat as patients. 9)The cost of case finding (including diagnosis and treatments of patients diagnosed) should be economically balanced in relation to possible expenditure on medical care as a whole. Case finding should be a continuous process and not a “once and for all ” project.

18. Aim The basic purpose of screening is to sort out from a large group of apparently healthy persons those likely to have the disease or at increased risk of the disease under study, to bring those who are " apparently abnormal" under medical supervision and treatment.

20. SCREENING V/S DIAGNOSTIC TESTS SCREENING TEST DIAGNOSTIC TEST Done on apparently healthy Applied to groups Test results are arbitrary and final Based on one criterion or cut off point Less accurate Done on those with indications or sick Applied to single patients, all diseases are considered Diagnosis is not final Based on evaluation of a number of symptoms, signs and laboratory findings More accurate

21. Less expensive Not a basis for a treatment Initiative comes from investigator or agency providing care More accurate Used as a basis for treatment Initiative comes from a patient with a complaint

22. CONCEPT OF “LEAD TIME” “Lead time” is the advantage gained by screening, that is, the period between diagnosis by early detection and diagnosis by other means… Detection program should be restricted to those condition in which there is considerable time lag between disease oneset and usual time of diagnosis..

23. POPULATION SCREENING …………..defined as application of a test to asymptomatic people to detect occult disease or a precursor state (Alan Morrison, screening on chronic disease, 1985 ) Familiar examples of use of population screening are cancer screening..

24. When to screen?

25. SCREENING REQUIREMENTS 1) Suitable disease 2) Suitable test 3) Suitable program 4) Good use of resources

26. 1)Suitable disease - serious consequences if untreated - detectable before symptoms appear -better outcomes if treatment begins before clinical diagnosis 2) Suitable test - detect during pre-symptomatic phase - safe - accurate - acceptable,cost effective

27. 3) Suitable program - reaches appropriate target population - quality control of testing - good follow up of positives - efficient 4) Good use of resources - costs of screening tests - cost of follow up-diagnostic tests - cost of treatment - benefits v/s alternatives

28. USES OF SCREENING Four main uses : A) Case detection – also known as “ prescriptive screening”. It is defined as the presumptive identification of unrecognised disease,which does not arise from patient’s request. Eg: neonatal screening. B) Control of disease – also known as “prospective screening”. The people are examined for the benefit of others. Eg: screening of immigrants from infectious diseases

29. C) Research purposes - e.g. cancer, hypertension. Screening may aid in obtaining more basic knowledge about the natural history of such diseases. D) Educational opportunities - screening programs (as for example, screening for diabetes) provide opportunities for creating public awareness and for educating health professionals.

30. Types of Screening Mass screening High risk selective screening Multiphasic screening

31. Types of Screening a.) Mass screening - it is offered to all, irrespective of the particular risk individual.

32. b.) High risk or selective screening Screening will be most productive if applied selectively to high risk groups, the groups defined on the basis of epidemiological research. More recently, epidemiologists have extended the concept of screening for disease to screening for "risk factors"

33. c.) Multiphasic screening the application of two or more screening tests in combination to a large number of people at one time than to carry out separate screening tests for single diseases.

34. Criteria for Screening The criteria for screening are based on two considerations: DISEASE to be screened TEST to be applied.

35. 1- Disease: the disease to be screened should fulfill the following criteria before it is considered suitable for screening: The condition sought should be an important health problem (in general, prevalence should be high) The natural history of the condition, including development from latent to declared disease, should be adequately understood (so that we can know at what stage the process ceases to be reversible) There is a test that can detect the disease prior to the onset of signs and symptoms

36. Facilities should be available for confirmation of the diagnosis There is an effective treatment There is good evidence that early detection and treatment reduces morbidity and mortality The expected benefits (e.g, the number of lives saved) of early detection exceed the risks and costs. When the above criteria are satisfied, then only, it would be appropriate to consider a suitable screening test.

37. Criteria for Screening 2- Screening test The test must satisfy the criteria of: Acceptability Repeatability Validity Simplicity Safety Rapidity ease of administration cost.

38. Screening Test Concerned with a Functional Definition of Normality versus Abnormality Screening Test Normal Abnormal

39. 1) Acceptability- Test should be acceptable to the people at whom it is aimed. In general, tests that are painful, discomforting or embarrassing (e.g. rectal or vaginal examinations) are not likely to be acceptable to the population in mass campaigns

40. 2.) Repeatability- sometimes called reliability, precision or reproducibility. That is the test must give consistent results when repeated more than once on the same individual or material, under the same conditions. The repeatability of the test depends upon three major factors, namely observer variation, biological (or subject) variation and errors relating to technical methods.

41. A. Observer variation Types: 1.) Intra-observer variation or within observer variation: This is a variation between repeated observations by the same observer on the same subject or material at the same time… 2.) Inter-observer variation: This is a variation between different observers on the same subject or material, also known as between observer variation.

42. B. Biological (subject) variation The fluctuation in the variate measured in the same individual may be due to: (a) changes in the parameters observed. (b) variations in the way patients perceive their symptoms and answer (c) regression to the mean. observer variation may be checked by repeat measurement at the same time, biological variation is tested by repeat measurements over time.

43. C. Errors relating to technical methods Repeatability may be affected by variations inherent in the method, e.g. defective instruments, erroneous calibration, faulty reagents; or the test itself might be inappropriate or unreliable.

44. 3. Validity (accuracy) The term validity refers to what extent the test accurately measures which it purports to measure. In other words, validity expresses the ability of a test to separate or distinguish those who have the disease form those who do not Validity has two components : sensitivity and specificity

45. True Disease Status Screening Test PositiveNegativeTotal Positive True Positives (TP) False Positives (FP) TP+FP Negative False Negatives (FN) True Negatives (TN) FN+TN Total TP+FNFP+TNTP+FP+FN+TN Outcomes of a Screening Test

46. True positive – the test was positive and the individual did have the disease.. False positive – the test was positive and the individual did not have the disease.. False negative – the test was negative and the individual did have the disease.. True negative – the test was negative and the individual did not have the disease

47. Sensitivity - the ability of a test to identify correctly all those who have the disease, that is "true positive“… A 90% sensitivity means that 90% of the diseased people screened by the test will give a "true positive". Specificity - is defined as the ability of a test to identify correctly those who do not have the disease, that is " true negatives“…… A 90% specificity means that 90% of the non-diseased people give "true negative"

49. Predictive accuracy – depends upon sensitivity, specificity and disease prevalence.. positive predictive value is the proportion of all people with positive test who have the disease………. negative predictive value is the proportion of all people with negative test who do not have disease……….

50. Yield – is the amount of previously unrecognised disease that is diagnosed as a result of screening effort…..

51. Evaluation of a screening program A) Randomised controlled trials – ideally evaluation should be done by RCT in which one group (randomly selected ) recieves a screening test and a control which receive no such test.. B) Uncontrolled trials – sometimes uncontrolled trials are used to see if people with disease detected through screening appear to live longer after a diagnosis and treatment than patients who were not screened

52. C) Other methods – other methods of evaluation such as case control studies & comparison in trends between areas with different degrees of screening coverage..

53. Screening Services EPSDT – Early Periodic Screening, Diagnostic & Treatment services EPDST service is a medicaid’s comprehensive and preventive child health program for individuals under age 21. EPDST screening services must include – - comprehensive health and developmental history, including assessment of both physical and mental health development

54. - appropriate immunizations - lead toxicity screening for children - health education

55. Screening for oral cancer Oral cancer is a major health problem Oral cancer incidence on the increase Survival rates remain unchanged Easily accessible sites Long premalignant and early invasive phase Better Rx outcomes in early stages

56. Screening Tools for oral cancer Visual inspection Self Examination Toluidine blue Fluorescence imaging Exfoliate cytology/Brush biopsy Saliva Examination

57. Oral Visual Inspection Sensitivity 58 – 94 % Specificity76 - 98% Most widely evaluated test Warnakulasuriya KAAS et al., Bull WHO 1984; 62: 243- 250 Mehta FS et al., Cancer Detect Prev 1986; 9: 219-225 Mathew B et al., Br J Cancer 1997; 76: 390-394 Ramadas K et al., Oral oncol 2003; 39: 580-88

58. Toludine Blue Test Tested only in a few specified clinical settings High false negative and false positive rates

59. Oral Cytology Lesion has to be seen before the sample collection Yield is poor Interpretation highly subjective High false negative rates

60. Analysis of Saliva Increased levels 4 mRNA from the following genes Interleukin1 beta Ornithine decarboxylase antizyme1 Spermidine/spermine N1-acetyl transferase Interleukin8

61. Vizilite it is an oral cancer screening tool that may help the clinician more easily visualise suspicious lesions. It is not a diagnostic tool. kit contents : - chemi-luminescent device -30ml acetic acid - light stick holder

63. Objective  To evaluate the efficacy of oral cancer screening by visual inspection of the oral cavity in detecting early stages of oral cancer and in reducing mortality  To study the determinants of population compliance for intervention  To evaluate the cost effectiveness of intervention Sankaranarayanan R, Ramadas K et al., Lancet 2005; 365: 1927-1933

64. Map Showing Study Clusters INDIA T RIVANDRUM C ITY Kerala Indian Ocean Bay of Bengal Arabian Sea Vakkom Kadakavoor Kizhuvilam Azhoor Mangalapuram Andoorkonam Pothencode Kazhakuttam Sreekariyam Attipra Kadinamkulam Chirayinkil Anjuthengu Intervention Clusters Control Clusters T RIVANDRUM C ITY Arabian Sea

65. Screen positivity  White, red, nodular lesions suggestive of leukoplakia or eythroplakia  Oral submucous fibrosis  Suspicious ulcer or growth

66. Referral investigations  Clinical examination by dentist or clinical oncologist  Histological examination

67. Monitoring and Evaluation  Process measures Participation in screening Screen (test) positivity Compliance with referral for reference investigators  Intermediate outcomes Detection rates of precancers and cancer Programme sensitivity Positive predictive value of screening test to detect both precancers and invasive cancer Stage distribution of cancers Survival Case fatality rate  Final outcome Reduction in mortality from oral cancer