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1 st October 2010

Hormonal contraception and risk of venous thromboembolism: national follow-up study BMJ Sept 2009;339:b2890. 1 st October 2010. A critical appraisal by Mark Chadwick. Hormonal contraception and risk of VTE. Presentation of paper Critical appraisal Questions Thoughts for the weekend.

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1 st October 2010

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  1. Hormonal contraception and risk of venous thromboembolism:national follow-up studyBMJ Sept 2009;339:b2890 1st October 2010 • A critical appraisal by Mark Chadwick

  2. Hormonal contraception and risk of VTE • Presentation of paper • Critical appraisal • Questions • Thoughts for the weekend

  3. Introduction • Studies show increased risk in VTE on OCP • Higher in first yr • Higher with desogestrel / gestodene • Lower with levonorgestrel • Shift from 50mcg to 40-20mcg ethinylestradiol • Theoretical lower risk • Equivocal evidence

  4. Objective • To assess risk of VTE in current users of different types of hormonal contraception

  5. Methods • Stated Cohort study • Linkage of 4 National registries • Central personal registry • Prescriptions • Education • Health

  6. Methods • Study Population • 01 Jan 1995 – 31 Dec 2005 • All Danish women, 15-49 yrs • Prior Malignancy & CVD excluded • New diagnoses censored • Emigrants censored • Pregnancy excluded +12/+4wks

  7. Methods • End points • First time VTE diagnosis

  8. Methods • Groupings • Length = Sum of valid Rx – periods of no valid Rx

  9. Methods • Contraception Categories • Time of usage • Regime (OCP / POP / IUD) • Oestrogen dose • Progestogen • Current usage (<1yr, 1-4yrs, >4yrs) • POP type

  10. Methods • Statistics • Poisson regression • Time at risk (women yrs) • Number of VTEs • Group

  11. Methods • Confounders • drugs for DM, HT, Diuretics, β/Ca blockers, ACE-I, Statins • Schooling / Education

  12. Results

  13. Results

  14. Results

  15. Results

  16. Results • Age Related use • Young use newer OCPs , short intervals

  17. Results • VTE risk increased with • Age • Study period 1.05 (95%CI 1.04 – 1.06)/yr • Decreasing education • First year use • Some longer term use • POP No increased VTE risk cf non-users • Levonorgestrel /noresthisterone 0.59 (CI 0.33 – 1.04) • Desogestrel 1.1 (CI 0.35 – 3.41) • IUD • 0.89 (95CI 0.64 – 1.26)

  18. Discussion • Aims achieved • Factors causing VTE • Excluding cancer /CHD => increased risk estimate • Pregnancy / POP => decrease risk • Change over time • Better detection

  19. Discussion • Risk of sub-types OCP discussed • Oestrogen dose • Type of progestogen • Concern re desogestrel / gestodene • Length of use • 20mcg significant only when accounted • Strengths and limitations • Omission of BMI • Family Predisposition

  20. Take home Points • The risk of VTE • Decreases with dose of oestrogen • desogestrel / gestodene > levonorgestrel • Unchanged by POP & IUDs • Absolute risk of VTE in any COP in young women is <1:1000 user yrs

  21. Hormonal contraception and risk of VTE • Presentation of paper • Critical appraisal • Questions • Thoughts for the weekend

  22. AUTHOR

  23. Critical appraisal • Is the paper interesting and relevant? YES • Who wrote the paper? • Do they or the institution have a proven academic record? • Appropriate Experience • Area of Expertise • Previous publications

  24. Prof. Øjvind Lidegaard, Copenhagen, Denmark • 81 graduated Copenhagen University • 81-87 Clinical residences in neurology, internal medicine, gastro­enterology, psychiatry, pediatrics • 92 Specialist in O&G • 93-97 senior resident O&G at Herlev Uni Hospital • 97-06 Appointed consultant & associate Professor • 06- Professor of the Gynecological Clinic at Copenhagen Uni

  25. Prof. Øjvind Lidegaard, Copenhagen, Denmark • published 135 scientific publications • first author on 102 • Majority epidemiological studies on risk factors • female cancers • cardiovascular diseases • ‘96 dissertation on oral contraceptives and thrombotic strokes

  26. Prof. Øjvind Lidegaard, Copenhagen, Denmark • Member of Board of Directors, Danish Society of Medical Informatics, 1988–1993. • Head of “Working group on gynecological technology assessment and quality assurance”, Danish Society of Obstetrics and Gynecology (DSOG) 1990–1997. • Head of “Committee on postgraduate education”, DSOG, April 1992 to April 1996. • Head of “Scandinavian Committee on postgraduate education”, Scandinavian Society of Obstetrics and Gynecology (NFOG) August 1994 to August 1996. • Consultant in “Committee on postgraduate education”, Danish Medical Association, 1991–1996. • Consultant in WHO on the project “Obstetrical quality indicators”, 1991–1995. • Head of guideline group in gynaecological reproduction, DSOG, 2000–2008. • Member of guideline group in hormone replacement therapy, DSOG 2000–2003 • Member of guideline group in contraception, • DSOG 2000–2008. • Member of Climate and health working group, Danish Medical Association since 2008.

  27. INTRODUCTION

  28. Introduction • Title • Clear / Concise / Appropriate • YES • Was the study original? • No, but follow-up to original

  29. Introduction • Literature Review • Did the study introduction address the relevant points? • Yes • Method / Extent / Up to date • Yes

  30. Introduction • Hypothesis • Were the hypotheses/aims clearly stated? • YES • Purpose • Who sponsored - Uni , pharm companies ? who • Who benefits - • Need for answer - YES

  31. METHOD / DATA

  32. Methods 1 • Type of research? • Objective / Subjective / Questionnaire / Interview

  33. Methods 1 Type of research? Objective / Subjective / Questionnaire / Interview Was there Ethics approval? DATA PROTECTION ONLY AS NOT REQUIRED

  34. Methods 1 • Was there Validation? • YES … but .. • 10% VTE uncertain • Therefore of remainder • 97% imaged, 2% treated • 94% imaged & treated • Uncertainty <1% • NO 11%

  35. Methods 2 • Level of Evidence? • Ia Meta-analysis of RCCT • Ib RCCT • IIa controlled trial NOT randomised • IIb quasi-experimental study • III descriptive study • IV expert opinion

  36. Methods 2 Level of Evidence? Ia Meta-analysis of RCCT Ib RCCT IIa controlled trial NOT randomised IIb quasi-experimental study III descriptive study IV expert opinion

  37. Methods 3 • Was the study design appropriate? • Review - systematic or meta-analysis • Drug treatment - randomised controlled trail • Causation - case - control study • Prognosis - cohort study

  38. Methods 3 • Was the study design appropriate? • Review - systematic or meta-analysis • Drug treatment - randomised controlled trail • Causation - case - control study • Prognosis - cohort study • Unclear if historic • Previously was case-control !

  39. ….!!! Time Out !!!…..

  40. Cohort Study • an observational study that takes a group (cohort) of patients and follows their progress in order to measure outcomes such as disease or mortality rates, and make comparisons according to the treatments that patients received. A Daly, 2008

  41. Cohort Study

  42. Disease + Exposed Disease - Study population Disease + Non-exposed Disease - Cohort Study

  43. Case-Control Study • a study that starts with the identification of a group of individuals sharing the same characteristics (disease) and a suitable comparison group (no disease). All subjects are then assessed with respect to things that happened in the past that might be related to contracting the disease. A Daly, 2008

  44. Case-Control Study Exposed Cases Non-exposed Study Population Exposed Controls Non-exposed

  45. Disease + Exposed Disease - Study population Disease + Non-exposed Disease - Retrospective Cohort Study

  46. Cohort Analysis • Analysis of results is a matter of calculating and comparing rates, which are commonly expressed in terms of person-years of observation. • 1 person is observed for 10 years, = 10 person-years. • 2 years observation of 5 persons, = 10-person years. • The use of person-years is a convenient way to generate larger numbers for calculation of rates that are more stable than with smaller numbers over numerous timelines. J Last, enotes.com

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