Train the Trainer Course book - Cochrane Public Health Group

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Introduction of bias into the conduct of a primary study Recruit participants SELECTION BIAS Allocate to intervention and control groups ALLOCATION BIAS Intervention group CONFOUNDING (dissimilar groups) Control group Implement intervention INTEGRITY OF INTERVENTION Implement intervention Follow-up participants INTENTION- TO-TREAT WITHDRAWALS/ DROP OUTS Follow-up participants Measure outcomes BLINDING OUTCOME ASSESSORS Measure outcomes Analyse data DATA COLLECTION METHODS STATISTICAL ANALYSIS Analyse data 68
Types of bias in health promotion and public health studies Bias A systematic error or deviation in results. Common types of bias in health promotion and public health studies arise from systematic differences in the groups that are compared (allocation bias), the exposure to other factors apart from the intervention of interest (eg. contamination), withdrawals from the study (attrition bias), assessment of outcomes (detection bias), including data collection methods, and inadequate implementation of the intervention. The following sections of this unit describe the types of bias to be assessed using The Quality Assessment Tool for Quantitative Studies (http://www.city.hamilton.on.ca/phcs/EPHPP/) developed by the Effective Public Health Practice Project, Canada. Further information is also provided in the Quality Assessment Dictionary provided in the following pages. 1) Selection bias Selection bias is used to describe a systematic difference in characteristics between those who are selected for study and those who are not. As noted in the Quality Assessment Dictionary, it occurs when the study sample (communities, schools, organisations, etc) does not represent the target population for whom the intervention was intended. Examples: Results from a teaching hospital may not be generalisable to those in non-teaching hospitals Results which recruited volunteers may not be generalisable to the general population Results from low SES schools or inner city schools may not be generalisable to all schools Examples from www.re-aim.org Example: Eakin and her associates (1998) illustrate selection bias in a smoking cessation study offered to participants in a planned-parenthood program. They begin by explicitly reporting their inclusion criteria --female smokers between 15 and 35 years of age who are patients at a planned-parenthood clinic. During a routine visit to the clinic the patient services staff described the study and solicited participants. Those women who declined (n=185) were asked to complete a short questionnaire that included questions to assess demographics, smoking rate, and reasons for non-participation. Participants (n=518) also completed baseline demographic and smoking rate assessments. They tracked recruitment efforts and reported that 74% percent of the women approached agreed to participate in the study. To determine the representativeness of the sample two procedures were completed. First, based on information from patient medical charts, those who were contacted were compared on personal demographics to those who were not contacted. Second, participants were compared to non-participants on personal demographics and smoking rate. The study found that those contacted did not differ from those not contacted on any of the test variables. Also, the results suggested that participants were slightly younger than non-participants, but there were no other differences between these groups. This suggests that Eakin and her associates were fairly successful in contacting and recruiting a fairly representative sample of their target population. Example: The Language for Health (Elder et al., 2000) nutrition education intervention provides a good example of determining the representativeness of study participants to a given target population. The behaviour change intervention was developed to target Latino participants in English as a second language (ESL) classes at seven schools. To examine representativeness, the 710 participants in the study were compared to the overall Latino ESL student population in the city. This comparison revealed that the intervention participants did not differ from the general ESL student 69
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TRAIN-THE-TRAINER HANDBOOOK Two-day
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Contents Introduction .............
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Additional reading: Textbooks: Oliv
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2) ONCE REGISTRATIONS HAVE BEEN REC
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OUTLINE OF TWO-DAY WORKSHOP 9:00am
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Unit One: Background to Systematic
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Reviews of clinical interventions v
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FACILITATOR’S GUIDE Time required
Page 21 and 22: Unit Two: International Systematic
Page 23 and 24: FACILITATOR’S GUIDE Time required
Page 25 and 26: Unit Three: Resources Required Lear
Page 27: Formulate review question Establish
Page 31 and 32: Unit Four: Developing a Protocol Le
Page 33 and 34: Establish an Advisory Group whose m
Page 35 and 36: FACILITATOR’S GUIDE Time required
Page 37 and 38: Unit Five: Asking an Answerable Que
Page 39 and 40: To investigate both the implementat
Page 41 and 42: Process evaluations: these studies
Page 43 and 44: REFERENCES 1. Oliver S. 1997. Explo
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Page 47 and 48: Unit Six: Finding The Evidence Lear
Page 49 and 50: CA38392 (NCI) Language English Entr
Page 51 and 52: Where to locate studies a) Electron
Page 53 and 54: ADDITIONAL READING Harden A, Peersm
Page 55 and 56: 45. "Diet-Fat-Restricted"/ all subh
Page 57 and 58: Brunton G, Harden A, Rees R, Kavana
Page 59 and 60: 1. Start with the primary concept,
Page 61 and 62: 5. Because adolescent has no narrow
Page 63: 12. Complete searches 8-12 and 13-2
Page 67 and 68: Unit Seven: Data Abstraction Learni
Page 69: FACILITATOR’S GUIDE Time required
Page 74 and 75: population on gender, age, or educa
Page 76 and 77: 5) Data collection methods As highl
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Page 80 and 81: 11. Green J, Tones K. Towards a sec
Page 83 and 84: QUALITY ASSESSMENT TOOL FOR QUANTIT
Page 85 and 86: G) ANALYSIS (Q1) Is there a sample
Page 87 and 88: DICTIONARY for the Effective Public
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Page 91 and 92: F) WITHDRAWALS AND DROP-OUTS Q1 Ind
Page 93: C) CONFOUNDERS Strong Moderate Weak
Page 96 and 97: Emphasise that the criteria to appr
Page 98 and 99: Randomised controlled trial - criti
Page 100 and 101: calculation? Yes Partially No (Q2)
Page 102 and 103: Controlled before and after study -
Page 104 and 105: RATE THIS SECTION Strong Moderate W
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Page 108 and 109: Pope C, Mays N. Qualitative Researc
Page 110 and 111: Screening Questions 1 Was there a c
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Page 116 and 117: A Checklist for Evaluating Evidence
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Page 120 and 121: Where studies are more homogenous,
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esulting from some community interv
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Reviewers should use the RE-AIM mod
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Economic efficiency Harms Economic
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9. Swerrissen H, Crisp BR. The sust
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Exercise: Allow participants 20 min
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who had participated in their smoki
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Critical Appraisal Skills Programme
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2 points out of the possible 4 poin
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- search for non-English language s
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9. Were all important outcomes cons
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Train the Trainer Course book - Cochrane Public Health Group

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