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DEPARTMENT OF PEDIATRICS Research Seminar STUDY DESIGN 10/22/09

DEPARTMENT OF PEDIATRICS Research Seminar STUDY DESIGN 10/22/09. David H. Rubin, MD Chairman, Department of Pediatrics, St. Barnabas Hospital Professor of Clinical Pediatrics Albert Einstein College of Medicine. RESEARCH DESIGN (Jekel, 2007). ADDITIONAL STUDY DESIGNS. Medical record review

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DEPARTMENT OF PEDIATRICS Research Seminar STUDY DESIGN 10/22/09

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  1. DEPARTMENT OF PEDIATRICSResearch SeminarSTUDY DESIGN10/22/09 David H. Rubin, MD Chairman, Department of Pediatrics, St. Barnabas Hospital Professor of Clinical Pediatrics Albert Einstein College of Medicine

  2. RESEARCH DESIGN(Jekel, 2007)

  3. ADDITIONAL STUDY DESIGNS • Medical record review • Survey study

  4. CASE CONTROL STUDIES

  5. CASE CONTROL STUDY EXPOSURE? CONDITION OR PROBLEM YES YES NO RESEARCH POPULATION AT RISK TIME YES NO NO (Fletcher, 1996)

  6. CASE CONTROL STUDIES/RECENT LITERATURE • Pubmed search of “case control studies” • 356,299 studies identified • Case control studies and emergency medicine journals • Ann Emerg Med: 602 studies (1980-2007) • Jour Emerg Med: 197 studies (1984-2007) • Acad Emerg Med: 357 studies (1994-2007) • Ped Emerg Care: 288 studies (1985-2007)

  7. NESTED CASE CONTROL STUDY (Gordis, 2000) • Case control study “nested” in cohort study • Population identified and followed over time • Disease develops in some members of the population • Case control study of • Cases (disease develops) and • Controls (disease does not develop)

  8. ADVANTAGES OF CASE CONTROL STUDIES(Fletcher et al, 1996, Newman et al, 2001) • Relatively easy to perform • Can study several risk factors and rare diseases without waiting for disease to occur • Beneficial for diseases with long latency • High yield of information with relatively few subjects • Ability to examine a large number of predictor variables makes case control studies useful for generating hypotheses

  9. DISADVANTAGES OF CASE CONTROL STUDIES (Fletcher et al, 1996, Newman et al, 2001) • Information available may be limited • No direct method to estimate incidence or prevalence of a disease • Only 1 main outcome can be studied • In cohort and cross sectional studies, several outcomes can be examined • Biggest weakness is bias

  10. BIAS IN CASE CONTROL STUDIES(Fletcher 1996) • Investigators create the comparison groups – there is no waiting to see who becomes a case and who becomes a control • Cases and controls are comparable if: • Controls would have been defined as cases if they developed the condition under study • Cases and controls need to be members of the same “base population”

  11. COHORT STUDIES

  12. COHORT STUDY • T0 T1 • Population followed forward over time • Baseline: acute pharyngitis • Outcome: Prevention of rheumatic fever or glomerulonephritis • Admission Criteria?: Evidence of ß-hemolytic streptococcus vs pharyngeal inflammation

  13. COHORT STUDY CONDITION OR PROBLEM EXPOSURE? YES YES POPULATION TIME NO SAMPLE YES NO NO (Fletcher, 1996)

  14. CROSS SECTIONAL STUDIES

  15. CROSS SECTIONAL STUDY T0 • T1 • Collect data on 2 groups at 1 point in time • Compare group differences • Cholesterol levels in athletes vs. non athletes at a midwest university

  16. CROSS SECTIONAL DESIGN • Face to face interview • Mailed questionnaire • Emailed questionnaire • Telephone interview • Mailed interview with telephone F/U • Interview and observation

  17. RANDOMIZED CLINICAL TRIALS

  18. RANDOMIZED CONTROL TRIAL CONTROL ENROLL SUBJECTS EXPERIMENTAL RANDOMIZATION TIME 0; BASELINE T1; FOLLOWUP

  19. SURVEY STUDIES

  20. SURVEY STUDIES • Collect information about people to describe, compare, or explain • Knowledge • Attitude • Behavior

  21. SURVEY STUDIES • Features of good survey studies • Specific measurable objectives • Solid research design • Good choice of population or sample • Reliable and valid instruments • Comprehensive analysis • Accurate reporting of results

  22. MEASURABLE OBJECTIVES • Define aim of the study • Define hypothesis • Define outcomes • Define independent, dependant, and confounding variables

  23. SAMPLING OF POPULATION • Many options • Sample - subset of the population chosen for study (characteristics similar to larger group) • Representative sample – use an unbiased method to choose survey participants • All members of the pediatric clinic at SBH who are between 2 and 3 years of age • Children seen at the Pediatric Endocrine Clinic for any illness related to diabetes mellitus

  24. DESCRIPTIVE REPORTS

  25. DESCRIPTIVE REPORTS Description of a new aspect or new disease No comparison group needed Description is usually a basic statistic summary or profile of the group of cases Mean, SD, range, confidence intervals, correlation between variables

  26. MEDICAL RECORD REVIEW

  27. MEDICAL RECORD REVIEW • Uses pre-recorded patient focused data as the primary source of information in a research study • Physician, nurses notes • Ambulance call reports • Diagnostic tests • Clinic, administrative, government records • Computerized databases

  28. WHY SELECT THIS DESIGN? • Addresses issues that cannot be addressed with prospective studies • Effect of harmful exposures (no randomization possible) • Effect of potentially beneficial exposures • Occurrence of rare events • Studies of patterns of disease or behavior • Quality assurance studies • Studies where cases may be shared (trauma database) • Pilot studies for prospective studies

  29. DATA QUALITY • “Free form” quality of medical records may increase missing and/or erroneous data • Handwriting may be illegible or uninterruptible • May miss examining potential cases • Computer vs paper records • Data abstraction techniques require standardization

  30. SAMPLE SIZE • Usually determined based on the summary measure and the size/width of the confidence interval desired • An interval with a greater CI (eg 99% CI v 95% CI) is wider and more likely includes the true population value • The width of the CI depends on sample size

  31. SAMPLING • Select all cases within a given time frame • For nonconsecutive sampling it is best to choose probability sampling • Provides equal opportunity for each eligible case to be selected • Use random number generator • Triage level • Incidental sampling – choosing most easily accessible cases • Systematic sampling – choosing every xth case

  32. RELIABILITY • Very important • Any differences in data extraction by 2 different people? • Kappa • Value ranges from -1 (perfect disagreement) to 1 (perfect agreement) • K = [observed agreement (%) – expected agreement (%) / [100% - expected agreement (%)] • Try to achieve kappa of 0.6 or better (60% agreement)

  33. MINIMUM REQUIREMENTS FOR MEDICAL RECORD REVIEWS(Lowenstein, 2005) • Explicit protocols for case selection/exclusion • Abstractor training • Precise definitions of key variables • Use of standardized abstraction and coding forms • Monitoring of abstractor performance • Blinding of abstractors to study hypothesis and patient groups • Testing of interrater reliability

  34. QUALITY OF MEDICAL RECORD REVIEWS(Badcock, 2005) • Observational study of medical record reviews published in several emergency medicine journals • 107 articles analyzed • Clear aim reported in 93% • Standard abstraction forms: 51% • Interrater reliability: 25% • Ethics approval: 68% • Sample size/power: 10%

  35. METHODOLOGY FOR RETROSPECTIVE REVIEWS IN CHILD PSYCHIATRY • Conceive question • Literature review • Proposal methods • Create data abstraction instrument and manual • Sample size • Obtain IRB approval • Pilot study

  36. SAMPLE SIZE(Gearing 2006) • Estimate 10 charts per variable (Sackett, 1991) • Others estimate 5-7 charts/variable • Convenience sampling – select cases over specific time period • Quota sampling – predetermined number sampled • Systematic sampling – every “nth” case chosen

  37. PRACTICAL ISSUES • Check all possible CPT codes for diagnosis or procedure code • Febrile seizure may have been coded as seizure • Gastroenteritis may have been coded as viral syndrome • Pilot your Data Abstraction Form • Create detailed “Codebook” for your study • Especially critical if > 1 researcher on study

  38. REFERENCES • Fink A. How to design survey studies. Sage Publications, Thousand Oaks, CA. 2003. • Kline TJB. Psychological testing –a practical approach to design and evaluation. 2005. Thousand Oaks. Sage. • Friedman JN. Development of a clinical dehydration scale for use in children between 1 and 36 months of age. J Pediatr 2004:145:201-207.

  39. REFERENCES • Cumming RG, Le Couteur D. Benzodiazepines and risk of hip fractures in older people; a review of the evidence. CNS Drugs. 2003;17(11):825-837. • Ding R, McCarthy M, Li G. Patients who leave without being seen: their characteristics and history of emergency department use. Ann Emerg Med 2006;48:686-693. • Feinstein AR. Clinical Epidemiology. Philadelphia. WB Saunders. 1985 • Fletcher RH, Fletcher SW, Wagner EH. Clinical Epidemiology The Essentials. Philadelphia: Lippincott Williams and Wilkins, 1996. • Gordis L. Epidemiology 2nd edition. Philadelphia: WB Saunders, 2000.

  40. REFERENCES • Worster A, Haines T. Advanced statistics: understanding medical record review (MRR) studies. Acad Emerg Med 2004;11:187-192. • Lowenstein SR. Medical record reviews in emergency medicine: the blessing and the cure. Annals Emerg Med April 2005;45(4):452-455. • Babcock D et al. The quality of medical record review studies in the international emergency medicine literature. 2005;45(4):444-447. • Worster A. et al. Reassessing the methods of medical record review studies 2005;45:448-451. • Gearing et al. Methodology for Retrospective chart review in child adolescent psychiatry. J Can Acad Child Adoles Psychiatry 15:3:2006

  41. REFERENCES • Hellems MA, Kramer MS, Hayden G. Case control confusion. Ambulatory Pediatrics 2006;6:96-99. Altzema C, Ann Emerg Med 2004;44:169-174 • Horwitz RI, Feinstein AR. Methodologic standards and contradictory results in case control studies. Amer Jour of Med 1979;66:556-564. • Hurwitz ES, Barrett MJ, Bregman D et al. Public Health Service study of Reye’s syndrome and medications. Report of the main study. JAMA 1987;257:1905-11. • Jekel JF, Katz DL, Elmore JG, Wild DMG. Epidemiology, Biostatistics and Preventive Medicine 3rd edition. Philadelphia: Saunders, 2007.

  42. REFERENCES • Katz AR. Selection of cases and controls. Additional information is needed. Int J Cardiology 2007;doi:10.1016/j.ijcard206.12.047 • Levy JA, Bachur RG. Intravenous dextrose during outpatient rehydration in pediatric gastroenteritis. Acad Emerg Med 2007;14:324-331. • Newman TB, Browner W, Cummings SR, Hulley SB in Hulley SB et al. Designing Clinical Research. 2nd edition. Philadelphia: Lippincott, 2001. • Neuman MI, Kelley M, Harper MB et al. Factors associated with antimicrobial resistance and mortality in pneumococcal bacteremia. Jour Emerg Med 2006;32(4):349-357.

  43. REFERENCES • O’Brien KL, Selanikio JD, Hecdivert C et al. Epidemic of pediatric deaths from acute renal failure caused by diethylene glycol poisoning. Acute Renal Failure Investigating Team. JAMA 1998;279:1175-1180. • Panagiotakos DB, Rallidis LS, Pitsavos C et al. Cigarette smoking and myocardial infarction in young men and women: A case-control studyInternational Journal of Cardiology, Volume 116, Issue 3, 4 April 2007: 371-375. • Pierfitte C, Macouillard G, Thicoipe M et al. Benzodiazepines and hip fractures in elderly people. BMJ 2001;322:704-708. • Schultz CH, Koenig KL, Lewis RJ. Decisionmaking in hospital earthquake evacuation: does distance from the epicenter matter? Ann Emerg Med 2007;50:320-326.

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