Introduction to Study Designs II

Transcription

1 Introdution to Study Designs II Commonly used study designs in publi helth & epidemiologi reserh Benjmin Rihrd H. Muthmbi, DrPH, MPH Stte HIV Epidemiologist HIV Epidemiology Investigtion Setion PA Deprtment of Helth Affilition: Mnging Diretor, Institute of HIV/AIDS Surveillne & Epidemiology (ihase) Institutes of Epidemiology & Publi Helth, In. (IEPH)

2 Outline Introdution to Study Designs II Experimentl Studies: Rndomized Clinil/Controlled Trils (RCTs); Rndomized Community or Field Trils; Observtionl Studies: Cross-Setionl Studies; Cse-Control Studies; Cohort Follow-up/Longitudinl Studies: Retrospetive Follow-up/Longitudinl Studies; Prospetive Follow-up/Longitudinl Studies; Dynmi Surveillne Cohort Studies; Nested Cse-Control Studies;

3 Observtionl Studies: Cse-Control (CC) Studies Pst popultion of ses & E^ d (D=Disesed + Disesed) Order of Dt Colletion: Strt by defining nd sertining dt on ses nd ; Retrospetively (go bk in ) to sertin pst exposure; Strengths CC studies Require smller smple sizes nd re therefore reltively quik nd inexpensive; Cn study mny exposures; Are suitble for studying rre diseses; Weknesses CC studies re Subjet to rell bis nd other problems with sertinment of pst exposures; Subjet to bised seletion of ; Questionble temporl order of exposure nd outome; Not suitble for studying rre exposures;

4 Observtionl Studies: Cse-Control (CC) Studies Pst popultion of ses & E^ d (D=Disesed + Disesed) Relevnt Study Chrteristis & Key Ethil Implitions: Observtionl study with NO investigtor mnipultion of exposure or outome; Need for informed onsent depends on whether the study involves intertive reserh tivities tht would not otherwise be onduted for routine helth servie nd/or use of identifible dt, e.g. 1: interviews/tests/proedures require informed onsent if not prt of routine servie; e.g. 2: studies whih depend on reord bstrtion/hrt review do not require informed onsent if dt nnot be linked bk to (unlinked/blinded) from identifiers of subjets studied; Cse-ontrol studies my/my not be determined to be reserh depending on whether the study will led to findings generlizble to ny popultions similr to tht in whih study onduted; or if generlizble to ny soiety; IRB review is required if study is lssified s reserh; some my be exempt reserh or nonreserh if onditions for determintion re met;

5 Observtionl Studies: Cse-Control (CC) Studies Simple Anlytil Frmework Pst popultion of ses & E^ d (D=Disesed + Disesed) Strt t Anlytil Frmework: 2 x 2 tble D E b E^ d D^ Mesure of Effet: Odds Rtio OR=Exp. Odds mong ses / Exp. Odds mong OR= ( / ) / (b / d) = (. d) / (b. ) Interprettion of Mesure of Effet: Those with disese re X s more likely to hve ertin exposures thn those without the disese;

6 Observtionl Studies: Cse-Control (CC) Studies Simple Anlytil Frmework Pst popultion of ses & E^ d (D=Disesed + Disesed) Strt t Anlytil Frmework: 2 x 2 tble D E b E^ d D^ Mesure of Effet: Odds Rtio OR=Exp. Odds mong ses / Exp. Odds mong OR= ( / ) / (b / d) = (. d) / (b. ) Exmples of Applition of This Design: Cse-ontrol study exmining ontribution of highly tive nti-retrovirl therpy (HAART) for HIV to longer survivl - ses re those who re deesed (or with poor survivl) vs s those remining live or with long-term survivl Potentil Interprettion of Mesure of Effet: Those with disese (deesed) re X s less or more likely to hve ertin exposures (HAART) thn those without the disese (longer-term survivors);

7 Observtionl Studies: Cse-Control (CC) Studies Simple Anlytil Frmework Pst popultion of ses & E^ d (D=Disesed + Disesed) Strt t Anlytil Frmework: 2 x 2 tble D E b E^ d D^ Mesure of Effet: Odds Rtio OR=Exp. Odds mong ses / Exp. Odds mong OR= ( / ) / (b / d) = (. d) / (b. ) Exmples of Applition of This Design: Cse-ontrol study exmining ontribution of lte dignosis with HIV (dignosed with AIDS, dvned disese) to deth/poor survivl - ses re those who re deesed (or with poor survivl) vs s those remining live or with long-term survivl. Potentil Interprettion of Mesure of Effet: Those who died/hve poor survivl (ses) re re X s more likely to hve ertin exposures (lte dignosis/dvned disese or AIDS) thn (those without the disese/those who remin live/longer-term survivors); Publi Helth Solution: Sreening for HIV, erly dignosis, & ly tretment;

8 Observtionl Studies: Cse-Control (CC) Studies Simple Anlytil Frmework Pst popultion of ses & E^ d (D=Disesed + Disesed) Strt t Anlytil Frmework: 2 x 2 tble D E b E^ d D^ Mesure of Effet: Odds Rtio OR=Exp. Odds mong ses / Exp. Odds mong OR= ( / ) / (b / d) = (. d) / (b. ) Exmples of Applition of This Design: Cse-ontrol study exmining likely soure of holer outbrek in London (1849) or Hiti ( ) to holer disese/deth - ses re those who hd holer (or fter signs of holer) vs s those who did not hve the disese. Potentil Interprettion of Mesure of Effet: Those who hd holer/died of it (ses) re X s more likely to hve ertin exposures (drinking wter from ontminted soure) thn those without the disese ; Solution: London: John Snow removed pump hndle from wter soure used by those who got sik; Hiti: Providing len drinking wter nd wsh hnds;

9 Dr. John Snow Epidemiology nd Choler Control