1 Evidence based health SCREENING Dr.Hathaitip Tumviriyakul Diploma Family medicine,Hatyai Hospital Msc. Epidemiology LSHTM,UK

2 Objectives Understand 5 steps of evidence based health screening practice. Be able to perform a basic step of searching health screening evidence.

3 "Kill as Few Patients as Possible" - Oscar London Rule 31- Review the world literature fortnightly A Year of MEDLINE indexed journals Washington Monument 555 feet

4 Clinical state Best research evidence Patient preference Clinical expertise “Evidence-based medicine is the integration of best research evidence with clinical expertise and patient values” - Sackett, et al 2001 What EBM is

5 Step 4: Integrating with our clinical expertise and patient’s unique Step 5: Evaluating our effectiveness and efficiency and seeking ways to improve them for next time Step 1: Formulate an answerable question Step 2: Tracking down the best evidence Step 3: Critically appraising for its validity, impact, impact, applicability applicability How do we actually practiceEBM?

6 Background vs. Foreground Questions Background: what, where, why, how? Foreground: diagnosis, prognosis, treatment, … Experience with the disease background foreground Text books: -Pathophysiology -Anatomy -Physiology Ask the expert Journals Cochrane library Best evidence Novice Expert

7 Clinical Scenario ผู้ป่วยหญิง อายุ 47 ปี มาพร้อมสามีอายุรุ่น เดียวกันที่ OPD เพื่อขอตรวจ fecal occult blood tests (FOBT) เนื่องจากเพื่อนสนิทเพิ่ง ป่วยเป็นมะเร็งในลำไส้ ผู้ป่วยเชื่อว่า ป้องกันไว้ ดีกว่ารักษา ผู้ป่วยเชื่อว่า ป้องกันไว้ ดีกว่ารักษา Background knowledge: – Trials of FOBT screening ช่วยลดอัตราการตาย จาก colorectal cancer (CRC) –FOBTs อาจ Positive ได้จากหลายสาเหตุ (a high false positive rate) ซึ่งอาจจะต้อง confirm โดย colonoscopy ท่านจะ screening FOBT FOBT ในผู้ป่วยราย นี้หรือไม่

8 Step 1. The question Does FOBT screening improve survivor of colorectal neoplasms? –P opulation - relatively young, asymptomatic people at average risk of bowel cancer –I ndicator - FOBT screen –C omparator – no screen –O utcome - improve survivor of colorectal neoplasm

9 Step 1. The question Does FOBT screening improve survivor of colorectal neoplasms? –P opulation - relatively young, asymptomatic people at average risk of bowel cancer –I ndicator - FOBT screen* –C omparator – no screen –O utcome - improve survivor of colorectal neopla* Underline keywords; think of synonyms –stool guaiac screen –bowel cancer

10 Step 2: Track down the best evidence Low High Validity Low High Clinical Relevance PEARLS: high quality, relevant studies

11 Therapy Button * Means any letters “OR” synonyms PubMed via Google ((colorectal neopla* OR bowel cancer* )and mass screening)

12 Systematic review button ((colorectal neopla* OR bowel cancer* )and mass screening)

13

14 Strategies for Critical Appraisal of Studies on Screening Clinical Importance/ Test Accuracy Validity Applicability

15 Strategies for Critical Appraisal of Studies on Screening Validity

16 Validity asymptomatic diseaseIs there Randomised trial evidence that the intervention benefits people with asymptomatic disease? Were the methods for performing the test described in sufficient detail to permit replication? Were the data identified, selected,and combined in an unbiased fasion –Efficacy of the test : Bias ? Lead time bias,length time bias, volunteer bias

17 Study designs for Randomised Trials of screening Randomize screen Treat early disease outcome No screen Treat at usual time of presentation outcome Screen Early disease /RF detected Randomised Treat early disease or RF outcome Treat at usual time of presentation outcome No disease/ RF detected

18 Strategies for Critical Appraisal of Studies on Screening Clinical Importance/ Test Accuracy

19 Clinical Importance/Test Accuracy Are test characteristics presented? –Accuracy of the test :Sensitivity,Specificity –Feasibility of the test :Predictive value screeningeffectThe screening effect :how large and precise? –RR / OR,95% CI,p value –number need to screen (NNS) number of extra patients you need to screen to prevent one bad outcome 1 / ARR = NNS - Absolute Risk/Rate Reduction (ARR) = r0 -r1 = |CER-EER| CER=control event rate, EER =experimental event rate

20 Strategies for Critical Appraisal of Studies on Screening Applicability

21 Applicability Is test available and affordable in your setting? Would the consequences of the test help your patient? Inexpensive Easy to administer Impose minimal discomfort on the patients

22 Step 4: Integrating with our clinical expertise and patient’s unique Step 5 Step 5: Evaluating our effectiveness and efficiency and seeking ways to improve them for next time Step 1: Formulate an answerable question Step 2: Tracking down the best evidence Step 3: Critically appraising for its validity, impact, impact, applicability applicability How do we actually practiceEBM?