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6. Types of Descriptive Studies

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Course: Epidemiology and Pharmacoepidemiology
Book: 6. Types of Descriptive Studies
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Date: Thursday, 25 April 2024, 9:53 AM

Table of contents

1. Types of Descriptive Studies

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Descriptive studies, as the name implies, describe conditions or diseases. In particular, descriptive studies identify patterns in person, place, and time. These types of study involve no comparison group. They are merely descriptive. The most basic types are: a case report, a case series, an incidence study and a cross-sectional study and are briefly described in the following.


1.1. Case Reports and Case Series


These are descriptive studies of one (case study or case report) or a series of patients (case series) defined by eligibility criteria, and where the unfolding course of events (disease progression, therapies, outcomes, etc.) is described in detail and where interventions are not manipulated.  This study design is used to provide a detailed description of an uncommon disease or condition, a specific situation, or unique therapeutic approaches. Reports provide retrospective safety and efficacy details, as well as other clinical parameters (e.g., quality of life [QoL]) derived from cases of interest in their natural clinical setting.



A case series describes the person, place, and time information about a group of cases. It can be retrospective, looking back in time, or prospective, looking forward in time, and usually involves a small number of patients. Case reports and series permit discovery of new diseases, unexpected effects, and provide data for generating hypotheses although the generalisability of their findings is limited because of selection bias and lack of controls. Data from a case series may be used in analytic studies to investigate possible causal factors.


1.2. Incidence studies


An incidence study is set up to investigate the incidence of a disease by measuring the number of new cases of a disease or condition, during a specific time in a specific population. One advantage of incidence studies is that they allow calculation of true rates of disease occurrence for a better estimation of risk.


1.3. Cross-sectional studies


See also Descriptive Cross-sectional study

Examples for the three above mentioned types of descriptive studies based on infections with the West Nile virus:

  • Case reports describe individual data, (e.g., on a form, a report in a medical journal). West Nile virus in a transfusion or transplant recipient might be reported as a case report.
  • A case series for West Nile virus might be presented in a table that lists and describes all West Nile cases in the Northwest
  • An incidence study could use a map to display all the new West Nile cases in the north western United States in a defined year.