1. STUDY DESIGNS CHP400: Community Health Program- lI Mohamed M. B. Alnoor Research Methodology Observational / Descriptive Studies Case report Case series Cross sectional Ecological studies Present: Disease Past: Exposure Cross - section Cohort Case - control Present: Disease & Exposure Present: Exposure Future: Disease nbmmb Time is Key

2. CONTENT Classification of Study Designs Observational Studies Observational / Descriptive Studies o Case Reports o Case Series o Cross-sectional studies (Health Survey) o Ecologic studies

3. STUDY DESIGNS Experimental Observational Animal Experiment Human Intervention Clinical trial Analytical Case control Descriptive Case report Case series Cross section Ecological Cohort Research Methodology

4. STUDY DESIGNS Observational Studies non-experimental Observational: no intervention treatment and exposures occur in a “non-controlled” environment individuals can be observed: Research Methodology - prospectively - retrospectively - currently

5. STUDY DESIGNS Observational / Descriptive Studies Case Reports Careful and detailed report by one or more clinicians of the profile of a single patient e.g. previously un-described disease e.g. unexpected link between diseases e.g. unexpected new therapeutic effect e.g. adverse events Research Methodology

6. STUDY DESIGNS Observational / Descriptive Studies o exposures(i.e. a case report gave the clue that “oral contraceptives” use increases the risk of venous thromboembolism. o “Luck” in being the first to encounter an interesting case. o Rigor in diagnosis, testing and documentation of clinical findings Case Reports Research Methodology

7. STUDY DESIGNS Strengths over one million case reports indexed on Medline. uses language that is familiar to clinicians and easy to interpret. useful reminder about conditions, diagnoses etc. that are rarely seen in most practices. for researchers, case reports generate hypotheses that can be tested using other study designs. Research Methodology Observational / Descriptive Studies Case Reports

8. STUDY DESIGNS No appropriate comparison group. Cannot be used to test for presence of a valid statistical association. Since based on the experience of one person: --- presence of any risk factor may be purely coincidental --- Not a true epidemiologic design. Limitations: Research Methodology Observational / Descriptive Studies Case Reports

9. STUDY DESIGNS Limitations: Tendency to publish reports of strange conditions that have little relevance to daily practice. Some authors erroneously try to imply causation, therapeutic benefits, etc. Research Methodology Observational / Descriptive Studies Case Reports

10. STUDY DESIGNS Authors: Smart ER. Macleod RI. Lawrence CM. Title: Allergic reactions to rubber gloves in dental patients: report of three cases. Source: British Dental Journal. 172(12):445-7, 1992 Jun 20. Research Methodology Abstract: Three cases of allergy to rubber are described. The patients exhibited peri-oral rashes following dental treatment by personnel wearing latex rubber gloves. Two of the patients were aware of possible allergy to domestic rubber products but did not reveal this as part of their medical history. With the increase in numbers of dentists wearing rubber gloves it is probable that there will be many more such cases reported in the future. Rubber products must then be added to the list of potential allergens which may be of some importance to the practice of dentistry. Observational / Descriptive Studies Case Reports

11. STUDY DESIGNS Experience of a group of patients with a similar diagnosis. Cases may be identified from a single or multiple sources. Generally report on new/unique condition. May be only realistic design for rare disorders Research Methodology Case Series Observational / Descriptive Studies

12. STUDY DESIGNS Useful for hypothesis generation. Used as an early means to identify the beginning or presence of an epidemic. Can suggest the emergence of a new disease (i.e. AIDS). Informative for very rare disease with few established risk factors. Strengths: Research Methodology Case Series Observational / Descriptive Studies

13. STUDY DESIGNS Limitations: Lack of an appropriate comparison group Cannot be used to test for presence of a valid statistical association Not a true epidemiologic design. Research Methodology Case Series Observational / Descriptive Studies

14. STUDY DESIGNS Observational / Descriptive Studies Cross-sectional studies An “observational” design that surveys exposures and disease status at a single point in time (a cross-section of the population) time Study only exists at this point in time Research Methodology

15. STUDY DESIGNS time Study only exists at this point in time Study population No Disease Disease factor present factor absent factor present factor absent Prevalence Research Methodology Observational / Descriptive Studies Cross-sectional studies

16. STUDY DESIGNS Often used to study conditions that are relatively frequent with long duration of expression (nonfatal, chronic conditions). It measures prevalence, not incidence of disease. Not suitable for studying rare or highly fatal diseases or a disease with short duration of expression. Research Methodology Observational / Descriptive Studies Cross-sectional studies

17. STUDY DESIGNS Strengths: Provides prevalence estimates of exposure and disease for a well-defined population. Easier to perform than studies that require follow-up (hence relatively inexpensive). Can evaluate multiple risk (and protective) factors and health outcomes at the same point in time. Research Methodology Observational / Descriptive Studies Cross-sectional studies

18. STUDY DESIGNS Strengths: May identify groups of persons at high or low risk of disease Can be used to generate hypotheses about associations between predictive factors and disease outcomes Research Methodology Observational / Descriptive Studies Cross-sectional studies

19. STUDY DESIGNS Limitations : Prevalent rather than incident (new) cases are used – the exposure could be associated with survival after disease occurrence, rather than development of the disease Temporal sequence between exposure and disease cannot be established i.e. Which came first, chicken or the egg? Research Methodology Observational / Descriptive Studies Cross-sectional studies

20. STUDY DESIGNS Limitations : Usually don’t know when disease occurred. Rare events: a problem Quickly emerging diseases: a problem Research Methodology Observational / Descriptive Studies Cross-sectional studies

21. STUDY DESIGNS Health Survey Survey (n): Information gathered by asking a group of individuals the same questions related to their characteristics, attributes. Survey (v): The process of collecting such information Research Methodology Observational / Descriptive Studies Cross-sectional studies

22. STUDY DESIGNS Health Survey Reach a large number of respondents; Generate standardized, quantifiable, empirical data - as well as some qualitative data; and offers confidentiality / anonymity A good survey has the potential to Research Methodology Observational / Descriptive Studies Cross-sectional studies

23. STUDY DESIGNS Health Survey Surveys can be: o Descriptive: These surveys do exactly what they say - they describe. The goal is to get a snapshot - of your ‘respondents’ o Explanatory: These surveys go beyond description and attempt to establish why things might be the way they are Research Methodology Observational / Descriptive Studies Cross-sectional studies

24. STUDY DESIGNS Health Survey o Census: This is a survey that does not rely on a sample. A census surveys every single person in a defined or target population o Cross-sectional surveys: This type of survey uses a sample or cross-section of those respondents selected to represent a target population Surveys can involve populations or samples of populations: Research Methodology Observational / Descriptive Studies Cross-sectional studies

25. STUDY DESIGNS Health Survey Surveys administration : o Face to face o Telephone o Self-administered. o Electronic e.g. E mail Research Methodology Observational / Descriptive Studies Cross-sectional studies

26. STUDY DESIGNS Health Survey o thorough planning, o meticulous instrument construction, o comprehensive piloting, o deliberate execution, o and appropriate analysis Conducting a survey capable of generating credible data requires: Research Methodology Observational / Descriptive Studies Cross-sectional studies

27. STUDY DESIGNS Health Survey Survey questions can either be open or closed: : o Open questions: Open questions can generate rich and candid data, but it can be data that is difficult to code and analyze. o Closed questions: These questions force respondents to choose from a range of predetermined responses, and are generally easy to code and analyze statistically. Research Methodology Observational / Descriptive Studies Cross-sectional studies

28. STUDY DESIGNS Health Survey Considerations in questionnaire Construction: Providing clear background information and lucid instructions. Logical organization. Comprehensive coverage without undue length. User friendly and aesthetically pleasing layout and design. Research Methodology Observational / Descriptive Studies Cross-sectional studies

29. STUDY DESIGNS Ecologic studies Measures that represent characteristics of entire populations are used to describe disease and to postulate causal associations. Measure of interest is correlation between exposure rates and disease rates among different groups. Correlation coefficient (denoted as “r” ) Range of “r” is from –1.0 to 1.0 Revaluated in relation to difference from 0. Research Methodology Observational / Descriptive Studies

30. STUDY DESIGNS Ecologic studies Strengths: Cheap, quick, and simple (generally make use of secondary data) Limitations: Cannot link exposure-disease relationship at the individual level Uses average exposure levels rather than actual levels of exposure Inability to control for confounding factors Research Methodology Observational / Descriptive Studies

31. STUDY DESIGNS Ecologic studies Country A Country B Person Salt IntakeHyp. Salt IntakeHyp. 1 1Yes1Yes 2 1Yes1Yes 3 1Yes1No 4 3No1No 5 3No1No 6 3No2No 7 3No2No 8 5No2No 9 5No2No 10 5No2No Avg. 3.030% 1.5 20% EXAMPLE: Country A:Country B Prevalence-Hypertension 30% 20% Average Salt Consumption Moderate Low Research Methodology Observational / Descriptive Studies

32. STUDY DESIGNS Ecologic studies The “Ecologic Fallacy”: Erroneous conclusions based on grouped data Patterns observed on the aggregate level are not observed on the individual level Research Methodology Observational / Descriptive Studies

33. STUDY DESIGNS Research Methodology Observational / Descriptive Studies Summary Observational studies are the starting point. Case Reports, Case Series and Cross-sectional studies are useful for generation of hypotheses. Cross-sectional studies: -provide prevalence estimates of exposure and disease -may identify groups of persons at high or low risk of disease