Clinical Reasoning‎ > ‎Archive‎ > ‎

CES Prognosis

Session leader: Hillary Kunins, MD

April 20th, 2010

Click here for a Word document of this page

Scroll down for links to the supplemental articles needed to answer these questions

 

Clinical Epidemiology:  Questions

Prognosis

 1. Now that you’ve read Sackett, you’ve realized the critical importance of an “inception cohort,” in studies about prognosis. Think about the great heterogeneity in illnesses and conditions that you’re now familiar with; discuss how you’d construct (recruit) TWO inception cohorts for two different conditions, one fairly straightforward, and one that’d be more challenging. Discuss where/how you would find participants, and how you’d identify them as “patients.”

 

a.

 

b.

 

 

2. Read the abstract and first 2 pages of:

 

Seeff LB, et al. 45 year follow-up of Hepatitis C Virus Infection in Health Young Adults. Annals of Internal Medicine 2000; 132:105-111.

 

Neal KR, et al. Excess Mortality rates in a cohort of patients infected with the Hepatitis C virus: a prospective Study. Gut 2007; 56:1098-1104.

 

     a. Comment on the “cohorts” for each study.

 

     -Are either or both of these “inception cohorts”?  If so, in what way does it/they meet the definition of inception cohort? And, if not, why not?

 

     -How might the differences in cohorts influence difference in results?

 

     -Which of the results is more “valid” ?

 

 

3. Read the first 2 pages of the following article and answer the questions that follow:

 

Nishimura et.al, Echocardiographically documented mitral valve prolapse.  A long term follow-up of 237 patients. NEJM 313:1305 1985.

 

     -What are the reasons for referral and steps in the referral sequence for a patient receiving an echocardiogram for MVP in this study?  Vis-a-vis severity of disease, which patients would this sequence select?

 

     -What proportion of patients had auscultatory findings?  Vis-a-vis severity of disease, what does this tell you about the group studied?

     -Many studies of MVP define its echo presence as > 2mm of prolapse.  How does this study define it, what was the average degree of prolapse found, and what are the implications re-disease severity?

 

     -Does the severity of disease of these subjects strengthen or weaken the authors’ conclusions re-prognosis?

 

 

4. As you know, (observational) prognosis studies about treatment do not always agree with subsequent randomized data. One example: hormone replacement therapy for women INCREASES risk for cardiovascular events. Previous to the Women’s Health Study, prognosis studies suggested the opposite. Read the abstracts and first 2-3 pages of the following 2 articles and answer the following questions.

 

Grodstein F, et al. A Prospective Observational Study of Postmenopausal Hormone Therapy and Primary Prevention of Cardiovascular Disease. Annals of Internal Medicine (2000):133:933-941.

 

Kitahaha, et al. Early vs Deferred ART for HIV on Survival. NEJM (2009): 3601815-26

 

 

     a. In the Grodstein article, what are the ways the authors do and do not adhere to the “validity” standards discussed by Sackett? Can you determine what “went wrong” with the study based on Sackett’s principles?

 

 

HINT: do you feel this was an “inception” cohort in terms of who “did” and “did not” take HRT? What characteristic(s) of the cohort might have influence the findings? Specifically, how might the participants who did and did not take HRT differ, and in what way could this influence study results?

 

 

     b. Apply your analysis to the Kitahaha article. What did the authors do to address the potential limitations of the observational prognosis design.  How does this influence your confidence in its findings?

Comments