Case Reports and Case Series
Case reports and case series represent the most basic types of observational study designs. These studies describe the experiences of a single person (case report) or a group of people (case series) who have a specific disease or condition. Case reports and case series typically describe previously unrecognized diseases or unusual variants of a known disease process. Consequently, data from these studies are particularly useful for alerting the health community to the presence of a new disease and for generating hypotheses regarding possible causes. For example, initial case reports of opportunistic infections among previously healthy homosexual men alerted the health community to the presence of the human immunodeficiency virus (HIV) epidemic. The initial case series describing patients with nephrogenic systemic fibrosis (NSF) raised awareness of this previously unknown condition and motivated subsequent studies that ultimately led to the discovery of gadolinium contrast as the causal agent (Chap. 1).
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