An 11-month-old girl is brought to the pediatrician by her parents for a follow-up visit. The patient was recently diagnosed with a rare multisystemic syndromic disorder characterized by cognitive impairment, deafness, skeletal abnormalities, and coarse facial features. The disorder occurs in ~1 in 100,000 births, and the underlying cause is unknown. The parents ask about factors that may have contributed to the development of the rare disorder. Which of the following types of study designs would be most appropriate to address the parents' question?

Question

An 11-month-old girl is brought to the pediatrician by her parents for a follow-up visit.  The patient was recently diagnosed with a rare multisystemic syndromic disorder characterized by cognitive impairment, deafness, skeletal abnormalities, and coarse facial features.  The disorder occurs in ~1 in 100,000 births, and the underlying cause is unknown.  The parents ask about factors that may have contributed to the development of the rare disorder.  Which of the following types of study designs would be most appropriate to address the parents' question?

Quizplus · Accepted Answer

Explanation: 11ec2b69_be00_175e_8f63_172f59604874_MD0005_00 Observational studies are broadly classified as having a descriptive or an analytic design. Descriptive designs (eg, case report, case series, cross-sectional) describe patterns of disease in populations by time, place, and person. These studies help generate hypotheses about associations between risk factors and disease, such as a study showing that a high proportion of people with lung cancer are also smokers. Analytical designs (eg, case-control, cohort, some cross-sectional) test hypotheses about associations between risk factors and disease, such as a study that determines smoking is a statistically significant risk factor for lung cancer. The choice of study design to address a specific research question is guided by a study's objective, the disease of interest, its apparent association to risk factors, and feasibility constraints. In this question, the parents of an 11-month-old girl ask about factors that may have contributed to their daughter's development of a rare disorder (occurring ~1 in 100,000 births). This suggests that the parents want to identify risk factors associated with the disorder. To address the parents' question, the study must have an analytical design to test a hypothesis about the association between potential risk factors and the disorder (Choices B and C). The analytical study designs commonly used to identify potential risk factors for disease are the cross-sectional study and the case-control study. A cross-sectional study takes a snapshot of a population to estimate the prevalence of risk factors and disease simultaneously, so this study design may not capture sufficient individuals with a rare disease to draw any valid conclusions (Choice E). A case-control study is an analytical design in which potential participants are initially identified as cases based on disease status (ie, with a rare syndrome) or controls (ie, without a rare syndrome), and then the presence of past exposure to ≥1 risk factors of interest is determined in each group. Therefore, this study design purposely captures sufficient cases of the extremely rare disease to draw valid conclusions. (Choice D) A cohort study is an analytical study design that estimates and compares the risk of developing disease between exposed and nonexposed groups. In this case, the study must identify potential risk factors (ie, exposure, genetics) for disease. Educational objective: The case-control study is the most appropriate observational analytical design to identify potential risk factors for uncommon (rare) diseases.

An 11-Month-Old Girl Is Brought to the Pediatrician by Her