Case Control and Community Studies

Compare and contrast the cohort study approach with case-control studies. Determine which you believe is most effective and explain why. Provide specific examples to support your response or cohort studies.

Two of the main models for observational studies come in the form of the cohort study and case-control study models.  These two approaches serve as some of the major ways in which the clinician is able to “evaluate associations between diseases and exposures” (Song & Chung, 2011, para. 3).  Cohort studies work in a way so that the study can identify a group that of individuals and monitors their health over a period of time.  The individuals that are exposed to the agent that the study is observing form the index subjects, whereby the group that does not become exposed to the study are known as the control subjects (Fleming, 2008).  This form of study allows researchers to see the effects of being healthy and being exposed to a particular agent will have overtime on a group of subjects that have been identified before the testing and observation began.  A case-control model has two groups as well but gathers them differently.  Those exposed to the disease are known as the cases and those without the disease are the control.  The subjects are not preselected in this model (Fleming, 2008).  This makes the cohort study more effective based upon the notion that it will yield results based upon the frequency of disease in exposed and non-exposed individuals, meaning that it is more beneficial to the understanding of the contraction and spread of the disease.  For example, a study looking at a group of individuals that contract a particular form of cancer-based upon exposure will be more beneficial to the community on treatments and cures when observing how the disease is contracted which a cohort study does more effectively than a case-control study.

Identify the advantages and disadvantages of developing and utilizing the cohort study methodology over the case-control study. Provide specific examples to support your response.

The advantages from the quantitative method of cohort methodology come mostly from the way that a researcher is able to have complete information to their subject’s exposure and experience after exposure to the agent that is being studied. In addition, this allows for an opportunity for the researcher to study multiple outcomes related to specific exposure (Fleming, 2008).  Finally, the results from this methodology are very easy to interpret and understand for non-epidemiologists.  This can be seen in a study of the Framingham Heart Study, which is still ongoing and has provided the medical community with a great deal of knowledge and insight into the functionality of the heart (Song & Chung, 2011).  This is seen as better than the case-control study, which has the potential to have its information be based primarily on interviews with subjects and can be very biased.  The case-control study is also only concerned with one disease and cannot provide information on incidence rates of disease.  Though helpful, such as the Zhang study which examined associations with a rare congenital microtia, these sorts of studies are limited to the specific disease in question and cannot allow for the broader possibilities that a cohort study can (Song & Chung, 2011).    

Analyze the various factors that go into clinical trial methodologies (including randomization, historical controls, crossover studies, sample size, duration, and masking), and determine which presents the greatest challenges. Make at least two recommendations for addressing the challenges you have identified. Provide specific examples to support your response.

One of the greatest trials facing randomized clinical trials comes in the form of the actual randomization process.  It has been reported, “only 33% to 58% of published surgical trials describe a valid randomization process where the treatment assignment cannot be predicted” (Kao, Tyson, Blakely, & Lally, 2008, para. 10).  The study further goes on to identify a trial evaluating the screening of mammograms “randomized” based on date of birth, however this was questioned based on the notion of the patient anticipation could, “inadvertently influence whether a patient is considered to meet eligibility criteria” (Kao et al., 2008, para. 10).  A second trial facing this sort of clinical trial is from the sample sizes that a trial will have.  It is extremely hard to randomize an increasingly small group without having some sort of bias in the procedure.  For example, a study on a rare disease may only produce 10 participants for the clinical trial.  The researcher must not allow for some sort of bias to invade their means randomization, and then there still exists the question as to what the results will show on such a small sample size when the community that is affected by the disease could be much greater.

Compare the differences (not similarities) between community trials versus traditional randomized clinical trials (RCT). Determine if a community trial would produce more accurate results versus the RCT on sexually transmitted diseases. Provide specific examples to support your response. 

The community trial, as opposed to the clinical trial, studies the effect on a particular agent on the community as a whole.  Whereas a clinical trial will be performed to an assigned patient in a clinical setting, the community trial places interventions to each member of a community (Boslaugh, 2008).  Community trials do not have to face the blinding and double-blinding techniques that a clinical trial must face as the sample size is considerably larger.  Therefore, it is clear that a community trial on a sexually transmitted diseases would be more beneficial and provide better, more accurate results based upon one caveat, which is that the community as a whole must have been exposed to the disease in question.  

If the community is being studied on the contraction of Chlamydia but the vast majority of the population does not have the disease, then a clinical trial can be more useful as it will target specifically those with the disease.  However, if the disease is widespread, then the community trial is more effective because it will have a much larger sample size to pull from and can provide a number of details that a clinical trial with a small sample simply cannot.  This is backed by the notion that followed by the Indonesian Vitamin A study.  In this study, children were given vitamin A supplements to see if it would decrease child mortality rates.  As the study was conducted on multiple villages, the results that showed a 49% higher likely rate of mortality to those without the supplement carried more weight as there was a high number of individuals to draw data from and compare amongst - resulting in significant data saturation (Boslaugh, 2008).              

References

Boslaugh, S. (2008). Encyclopedia of epidemiology. Thousand Oaks, California: Sage Publications.

Fleming, S. T. (2008). Managerial epidemiology: Concepts and cases (2nd ed.). Chicago: Health Administration Press 

Kao, L. S., Tyson, J. E., Blakely, M. L., & Lally, K. P. (2008). Clinical research methodology i: Introduction to randomized trials. J Am Coll Surg., 206(2), Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2366892/

Song, J. W., & Chung, K. C. (2011). Observational studies: Cohort and case-control studies. Plastic Reconstruction Surgery, 126(6), Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2998589/