1. STUDY DESIGNS CHP400: Community Health Program- lI Research Methodology Observational / Descriptive Studies Case report Case series Cross section Ecological 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 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

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

5. Descriptive Studies Case Reports Careful and detailed report by one or more clinicians of the profile of a single patient ( few cases ) e.g. previously un-described disease e.g. unexpected link between diseases e.g. unexpected new therapeutic effect e.g. adverse events

6. Case Reports cont. A case report gave a 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

7. Tendency to publish reports of strange conditions that have little relevance to daily practice. Some authors erroneously try to imply causation, therapeutic benefits, etc.

8. Case Reports 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.

9. Case Reports No appropriate comparison group. Cannot be used to test presence of a 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

10. 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. 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. Case Reports

11. 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 Case Series Descriptive Studies

12. 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 risk factors. Strengths: Case Series

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

14. Descriptive Studies Cross-sectional studies An observational design that surveys exposures and disease status of a population at single point in time time Study only exists at this point in time

15. time Study only exists at this point in time Study population Not Diseased Diseased factor present factor absent factor present factor absent Prevalence Cross-sectional studies

16. Often used to study conditions that are relatively frequent with long duration (nonfatal, chronic conditions). It measures prevalence, not incidence of disease. Cross-sectional studies

17. 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 (protective) factors and health outcomes at the same point in time. Cross-sectional studies

18. 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 Cross-sectional studies

19. 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? Cross-sectional studies

20. Limitations : cont. Not suitable for studying rare or highly fatal diseases or a disease with short duration of expression. Cross-sectional studies

21. 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

22. Reach a large number of respondents; Generate standardized, quantifiable data - as well as some qualitative data; and offers confidentiality / anonymity A good survey has the potential to :

23. Surveys can be: o Descriptive: These surveys do exactly what they say - they describe. The goal is to get a snapshot - of your ‘respondents’ Explanatory: These surveys go beyond description and attempt to establish why things might be the way they are

24. o Census: A census surveys every single person in a defined or target population.This is a survey that does not rely on a sample. 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 population or samples of populations:

25. Surveys administration : o Face to face o Telephone o Self-administered. o Electronic e.g. E mail

26. o comprehensive planning, o meticulous instrument construction, o comprehensive piloting, o Deliberate implementation o and appropriate analysis Conducting a survey capable of generating credible data requires:

27. Survey questions can be : : o Open questions: Open questions can generate rich 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 statistically analyze.

28. Considerations in questionnaire Construction: Providing clear background information and lucid instructions. Logical organization. Comprehensive coverage without undue length. Uses of friendly and nice pleasing layout and design.

29. 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 is from –1.0 to 1.0 Revaluated in relation to difference from 0. Ecologic studies

30. 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

31. 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

32. The “Ecologic Fallacy”: wrong conclusions based on grouped data Patterns observed on the aggregate level are not observed on the individual level

33. 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 risk of disease