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Design of Observational and Experimental Clinical Studies

Design of Observational and Experimental Clinical Studies. Kenneth F. Schulz, PhD. Epidemiology. More than statistics; biostatistics; medical science - A specific research methodology “Methods” conjures up what images? Connotation? Word association? Presentation? NEJM Methods Section

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Design of Observational and Experimental Clinical Studies

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  1. Design of Observational and Experimental Clinical Studies Kenneth F. Schulz, PhD

  2. Epidemiology • More than statistics; biostatistics; medical science - A specific research methodology • “Methods” conjures up what images? • Connotation? Word association? Presentation? • NEJM Methods Section • Bad Rap - really fun and exhilarating

  3. Epidemiology of AIDS Before HIV • Risk groups identified • MSM • Blood recipients • IVDU • > 100 partners/year (implying that 99 are safe…) • Anal receptive intercourse/fist • Not using condoms Nash Herndon/FHI

  4. AIDS Prevention Before HIV • Exclusion of risk groups from blood donation • Education/recommendations on the risk factors

  5. AIDS Prevention Before HIV: Effects • Transfusion associated, transmission dropped • In certain areas, risk factor transmission dropped, witness the 90% reduction in syphilis in San Francisco • Supported by subsequent HIV analysis of banked blood

  6. Bacterial Vaginosis and Prematurity in Indonesia* • Association between bacterial vaginosis diagnosed at 16 to 20 weeks and preterm delivery(gestational age <37 weeks) • OR = 2.0; 95% CI 1.0 - 3.9 • Above OR adjusted for mother’s age, education, smoking and Trichomonas *Joesoef et al. Am J Obstet Gynecol 1993;169:175-8.

  7. Bacterial Vaginosis and Prematurity in Indonesia* (Cont.) • “Only bacterial vaginosis diagnosed early in the second trimester of pregnancy plays a major role as a risk factor for preterm delivery” • Clindamycin vaginal cream - an effective treatment *Joesoef et al. Am J Obstet Gynecol 1993;169:175-8. Nash Herndon/FHI

  8. Begin Program in Indonesia? • PPE • Conduct an RCT • Corollary to PPE: SE

  9. Intravaginal Clindamycin for BV: Effects on Preterm Delivery and LBW* *Joesoef et al. Am J Obstet Gynecol 1995; 173:1527-31.

  10. Study Design is Critical • Reading the literature • No study is perfect – the limitations MUST be understood • Conducting research • Serious mistakes in the study design stage cannot be corrected in subsequent stages

  11. Types of Epidemiologic Studies • Observational: “natural experience” • Descriptive: • like newspaper reporting • has no control or comparison group • Analytic: • has a control or comparison group • Experimental: investigator controls • has an exposed or experimental group plus a control or comparison group determined by investigator complexity

  12. Descriptive Studies • Estimate frequency • Time trend • Generate more specific etiologic hypotheses

  13. IUD PID? Descriptive Study of Womenwith PID Exposure (STI, IUD) Outcome (PID) © Ruth C. Kennedy © Harvey Nelson SES (Age, Marital Status, Etc.)

  14. Cohort Exposure Exposed Outcome? Not Exposed Outcome? Exposed? Outcome Exposed? Control Case-Control Outcome Observational Analytic Studies

  15. The Future Population Outcome No Outcome Outcome Sample No Outcome Exposurepresent Exposure absent Prospective Cohort Design The Present

  16. The Future Population Death No Death Death Sample No Death PTXpresent PTX absent Example of a Prospective Cohort Design: Treatment of Severe Malaria in Children The Present

  17. Case-Control Design The Past or PresentThe Present Sample of cases Exposure present Exposure absent Outcome Population with disease (cases) Sample of controls Exposure present Exposure absent No Outcome Much larger population without disease (controls)

  18. Example of Case-Control Design: OC Use and Breast Cancer The Past or PresentThe Present Sample of cases Breast Cancer OC Use OC Use absent Population with disease (cases) Sample of controls OC Use OC Use absent No Breast Cancer Much larger population without disease (controls)

  19. Randomize Sample (Subset) Unexposed Exposed Outcome Assessment RCT Paradigm Population of Interest Other allocation approach?

  20. RCT Paradigm Women with Postpartum Febrile Morbidity Randomize New Antibiotic Ampicillin Sample (Subset) Outcome Assessment Recovered within 7 days

  21. During the Emergence of Modern Epidemiology(around 1950) • Sir Austin Bradford Hill, Sir Richard Doll and colleagues conducted: • A case-control study of lung cancer • A cohort study of smoking and lung cancer • The first RCT in medicine, streptomycin for treatment of TB

  22. END

  23. Epidemiologic Goals • Read the literature more critically • Ability to conceptualize EPI research designs • Implement simple designs • Seek assistance from the appropriate people and ask the right questions

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