Individual exercises
Consider the following study types:
A. Experimental
B. Observational cohort
C. Observational case-control
D. Observational cross-sectional
E. Not an analytical or epidemiologic study
For each of the following studies described below, classify each as one of the above study types, and discuss the strengths and weaknesses of each study from their description.
-
Representative sample of residents were telephoned and asked how much they exercise each week and whether they currently have (have ever been diagnosed with) heart disease.
-
Occurrence of cancer was identified between April 1991 and July 2002 for 50,000 troops who served in the first Gulf War (ended April 1991) and 50,000 troops who served elsewhere during the same period.
-
Persons diagnosed with new-onset Lyme disease were asked how often they walk through woods, use insect repellent, wear short sleeves and pants, etc. Twice as many patients without Lyme disease from the same physician’s practice were asked the same questions, and the responses in the two groups were compared.
-
Subjects were children enrolled in a health maintenance organization. At 2 months, each child was randomly given one of two types of a new vaccine against rotavirus infection. Parents were called by a nurse two weeks later and asked whether the children had experienced any of a list of side-effects.
Group exercises
Read the following cases, and then for each case answer the question below.
Case 1: Sickle cell disease (SCD) is endemic in non-Western countries. Due to migration, the prevalence of SCD in the Netherlands has increased. Adherence to medical treatment is recognized as a major problem area. Therefore, new effective interventions to increase adherence are urgently needed.
Case 2: Growth of children affected by Sickle Cell Disease (SCD) is not well described in sub-Saharan Africa despite the high prevalence of the disease. Few data are available in this context and on the issue using the World Health Organization growth norms. We therefore conduct the present study with the aim of describing the growth of affected children aged less than 5 years. We also assessed correlation of anthropometric parameters with disease severity criteria.
Case 3: Pulmonary embolism (PE) is a leading cause of morbidity and mortality in the U.S. We and others previously have shown that PE is increasingly detected with increasing use of spiral computerized tomography (CT), at lower severity of illness, suggesting earlier PE diagnosis. Although thrombosis is increased in those with sickle cell trait (Austin, Blood 2007), data are lacking on the prevalence and predictors of PE among individuals with sickle cell disease (SCD), in whom thrombosis may be driven by hemolysis-associated endothelial dysfunction and platelet aggregation.
Case 4: Clinical Outcomes and Healthcare Utilization in Patients with Sickle Cell Disease: There is limited contemporary evidence on clinical outcomes and healthcare use in sickle-cell disease (SCD) patients enrolled in US Medicaid. We aimed to provide contemporary estimates for rates of vaso-occlusive crises (VOC), mortality, and healthcare resource utilization (HRU) in SCD patients enrolled in US Medicaid.
Question: For each case described above:
- Name the most appropriate study design to answer that research question
- Motive why you have selected that type of study design
- Give the strength and limitation of the study design of your choice