A group of infectious disease specialists interested in the rising prevalence of multidrug-resistant tuberculosis conducts a study to determine predisposing risk factors for the condition. First, they identify 40 patients with multidrug-resistant (MDR) tuberculosis and 64 with pansensitive tuberculosis who were admitted to the hospital over the last 5 years. They then review the patients' past medical records and consider demographic characteristics, previous anti-tuberculosis treatment, HIV status, and major comorbidities as potential risk factors for MDR tuberculosis development. They then compare the frequencies of these potential risk factors between the groups. Which of the following best describes the study design being used?

Question

A group of infectious disease specialists interested in the rising prevalence of multidrug-resistant tuberculosis conducts a study to determine predisposing risk factors for the condition.  First, they identify 40 patients with multidrug-resistant (MDR) tuberculosis and 64 with pansensitive tuberculosis who were admitted to the hospital over the last 5 years.  They then review the patients' past medical records and consider demographic characteristics, previous anti-tuberculosis treatment, HIV status, and major comorbidities as potential risk factors for MDR tuberculosis development.  They then compare the frequencies of these potential risk factors between the groups.  Which of the following best describes the study design being used?

Quizplus · Accepted Answer

11ec25c8_d323_5e63_bc81_43572d0367c4_MD0003_00 Observational epidemiological studies (eg, case series, case control, cohort, and cross-sectional studies) differ from experimental studies (eg, clinical trials) in that the researchers passively observe the study participants rather than monitor the result of a specific intervention. Observational studies can be subdivided into descriptive and analytical. Descriptive epidemiology deals with the collection of data to characterize a specific health problem (eg, disease prevalence; incidence rates; distribution over time, location, and demographics). Analytical epidemiology is used to test hypotheses generated after analyzing the data from descriptive studies (eg, risk factor associations). Case control studies are analytical observational studies that retrospectively associate outcomes with specific risk factors. The researcher first begins by selecting cases with a certain outcome of interest (eg, multidrug-resistant tuberculosis [MDR TB] infection) and controls without that outcome (eg, pansensitive tuberculosis infection). As seen in this example, controls do not need to be disease-free but rather do not have the outcome of interest (eg, controls have pansensitive tuberculosis, not MDR TB). The cases and controls are then assessed retrospectively for the presence of risk factors (eg, HIV, comorbidities, previous anti-tuberculosis treatment). Exposure to risk factor status is determined by such activities as personal interviews and analysis of health records and laboratory reports. The critical distinction between case control and retrospective cohort studies is the order in which outcomes and risk factors are assessed: case control studies first determine the outcome (eg, MDR TB) and then look for associated risk factors (eg, HIV, previous anti-tuberculosis treatment); retrospective cohort studies ascertain risk factor exposure (eg, HIV) and then determine the outcome (eg, MDR TB). (Choice B) Cross-sectional studies are observational studies that can be either descriptive or analytical depending on study design. Since they assess both exposure and outcome at a single point in time, they can show that an association exists but cannot establish causation. (Choice C) Prospective cohort studies are analytical observational studies in which a group of exposed and unexposed individuals (eg, patients with and without HIV) is followed prospectively over time for development of the outcome of interest (eg, MDR TB). Cohort studies are considered stronger than case control and cross sectional studies because of their greater ability to prove causation. (Choice D) A randomized control trial is an experimental study that is considered the gold standard for studying the efficacy of a treatment or procedure. Subjects are randomly assigned to an experimental or control group and monitored for the outcome of interest. This study design often has the least bias and provides the strongest evidence for a causal relationship. (Choice E) A retrospective cohort study is similar to a prospective cohort study except that risk factor exposure and the outcome of interest both occur in the past and are assessed through review of records. Unlike a case control study, however, risk factor exposure is determined before the outcome is known (ie, first identify patients with and without HIV and then see if they develop MDR TB), thus allowing calculation of the relative risk. Educational objective: The critical distinction between case control and retrospective cohort studies is the order in which outcomes and risk factors are assessed. Case control studies determine the outcome first and then look for associated risk factors; retrospective cohort studies first ascertain risk factor exposure and then determine the outcome.

A Group of Infectious Disease Specialists Interested in the Rising