Biostatistics Study Design
A. Case-control studies Care-control studies are retrospective and are as described in the question stem. Case-control studies allow researchers to compute an odds ratio.
A group of patients with lung cancer is matched to a group of patients without lung cancer. Their smoking habits over the course of their lives is compared. On the basis of this information, researchers compute the rate of lung cancer in patients who smoke versus those who never smoked. This is an example of a A. case-control study B. cohort study C. cross-sectional study D. longitudinal study E. randomized control study
(C) Longitudinal In a longitudinal study, the same group is followed over a long period of time. Generally, no active intervention is instituted after the initial event. Note that the event may be either negative or positive.
In a study, a group of people are exposed to an environmental toxin but are not treated. Instead, they are observed over time on a standard set of measures to ascertain the potential effects of the toxin. This type of study design is called (A) Clinical trial (B) Double-blind (C) Longitudinal (D) Prospective (E) Retrospective
(D) This study is an observational study. The study described above is an example of a cross-sectional study. A survey is taken at a particular point in time to determine the prevalence of disease in this population. Risk factors can be assessed at this same time, but these studies cannot be used for determining causation because the studies are purely observational. The disease prevalence can be estimated in a cross-sectional study.
A health department wants to understand the healthcare needs of their population. They send a survey to the residents of the town. From this survey, they learn that 32% of the population currently has asthma and 38% of the population currently smokes cigarettes. Which of the following is true? (A) The relative risk is the best statistic to be calculated from this data (B) This study can be used to determine disease incidence (C) This study is a retrospective study (D) This study is an observational study (E) This study shows that smoking cigarettes causes asthma
(C) This is a phase II clinical trial. The study described above is a phase II clinical trial. In clinical trials, new medications are tested on human subjects for the first time. The goal of the clinical trials is to attain approval from the Food and Drug Administration (FDA) to be able to market the medication. These studies are divided into phases. Phase II clinical trials begin after the drug passes the phase I clinical trials. In these studies, a small number of participants with the disease are enrolled. The participants are divided into two groups- one receiving the drug and one receiving the placebo. These are typically double-blinded studies as neither the participant nor the researcher knows who is taking the medication being studied. In these studies, it is determined whether or not the new drug is effective in treating the disease of interest.
A new drug is developed for the treatment of asthma. It has been tested on a small group of healthy volunteers and was determined to be safe for use in patients with asthma. A study is conducted with 200 participants with a history of asthma. Half the participants are provided the medication, and the other half are provided with a placebo. Neither the investigators nor the participants know what treatment they have received. Which of the following is true? (A) Once the drug passes this study it can be approved for distribution without further testing (B) This is a phase I clinical trial (C) This is a phase II clinical trial (D) This is a single-blind study (E) This study can be used to determine if the new medication is more effective than the current standard of treatment
(E) double-blind randomized clinical trial This is an example of a placebo controlled, double-blind randomized clinical trial. In this type of study, subjects with a particular disorder are randomized (the lottery) to receive either the treatment in question or a placebo. The information about whether the patient receives the treatment or the placebo is not known to either the subject or the investigator (double blind). This type of study may be used to infer causality, i.e., if the patients taking the medication have more CD4+ T cells than the other group, it is due to the drug in question.
A new drug with in vitro activity against HIV is tested on a population of patients with Western-blot confirmed HIV infections. Out of the 200 individuals in the patient population, IOO individuals are chosen by lottery to receive the drug. The drug, which is tasteless, is administered in a cup of orange juice; the other patients receive pure orange juice. Neither the nurses, doctors, nor patients know which patients receive the drug. At • the end of the study period, the number of CD4+ T cells is determined for all of the subjects. This is an example of a (A) case-control study (B) case report (C) cohort study (D) cross-sectional study (E) double-blind randomized clinical trial
(C) This study can be used to assess the toxicity of the medication. The study described above is a Phase I clinical trial. In clinical trials, new medications are tested on human subjects for the first time. The goal of the clinical trials is to attain approval from the Food and Drug Administration (FDA) to be able to market the medication. These studies are divided into phases. The first phase is described in the scenario above. In phase I trials, a small number of healthy participants are recruited to the study. In these trials, the participants are given medications at increasing doses. They are then assessed for adverse events and provide regular blood samples. From this information, the researchers are able to determine toxicity of the medication and pharmacokinetic properties.
A new treatment is being developed for diabetes mellitus. Researchers first enroll a group of 70 healthy participants without diabetes into the study. Each participant is given the new medication at increasing doses and returns to the study to provide blood samples. Which of the following is true of this study? (A) This is a phase II clinical trial (B) This is a phase Ill clinical trial (C) This study can be used to assess the toxicity of the medication (D) This study can be used to determine efficacy of the medication on treating diabetes mellitus (E) This study can be used to determine whether the medication is more effective than the current standard of treatment for diabetes mellitus
(B) This is a retrospective study The study above is a case-controlled study. Case-controlled studies recruit participants that either have or do not have the particular disease. These participants are then asked whether or not they have had a particular exposure or risk factor. This is both an observational study and a retrospective study. There are no interventions taken, and causality cannot be determined. The odds ratio is the best statistic for analyzing the data in case-controlled studies.
A study is conducted to determine the role of cigarette smoking on the development of chronic obstructive pulmonary disease (COPD). A group of 2500 people is recruited for the study. Half of the people have been diagnosed with COPD, and the other half is without the disease. The participants are then asked whether or not they smoked at any point in their lives. Which of the following is true about this study? (A) The relative risk should be calculated from the data (B) This is a retrospective study (C) This study can be used to determine if smoking causes COPD (D) This study can be used to estimate disease incidence (E) This study can be used to estimate disease prevalence
(B) Cohort study Cohort studies are observational and prospective. Participants are divided into groups based on exposure and then followed for development of the disease. In this case, the participants are divided based on the presence or absence of a first-degree relative who has been diagnosed with breast cancer. They are then followed for a period of 10 years to determine whether the participants develop breast cancer. The relative risk is the statistic used for identifying the increased risk for developing disease in people with a particular risk factor.
A study is conducted to determine whether people with a first-degree family relative with breast cancer are at increased risk for development of breast cancer. One thousand participants are recruited for the study. Four hundred people have a first-degree family relative with breast cancer, and 600 people do not. These participants are followed for 10 years. At the end of the study, 140 people with a family history of breast cancer developed breast cancer while 80 people without a family history were diagnosed. Which of the following types of studies is described above? (A) Case-controlled study (B) Cohort study (C) Cross-sectional study (D) Double blind study (E) Meta-analysis
(C) case-control study Case-control studies begin with the identification of subjects who have a specific disorder (cases-i.e., ulcer patients) and subjects who do not have that disorder (controls-i.e., those diagnosed with other disorders). Information on the prior exposure of cases and controls to risk factors is then obtained. In this case-control study, the investigators used cases (ulcer patients) and controls (patients with other disorders) and looked into their histories (hospital records), to determine the occurrence of the risk factor (i.e., emotional stress) in each group.
A study is designed to determine the relationship between emotional stress and ulcers. To do this, the researchers used hospital records of patients diagnosed with peptic ulcer disease and patients diagnosed with other disorders over the period from July 1988-July 1998. The amount of emotional stress each patient was exposed to was determined from these records. This study is best described as a (A) cohort study (B) cross-sectional study (C) case-control study (D) historical cohort study (E) clinical treatment trial
(E) clinical treatment trial This study is best described as a clinical treatment trial-a study in which a cohort receiving a new antihistamine is compared with a cohort receiving a placebo
A study is done to determine the effectiveness of a new antihistamine. To do this, 25 allergic patients are assigned to one of two groups, the new drug (13 patients) or a placebo (12 patients). The patients are then followed over a 6-month period. This study is best described as a (A) cohort study (B) cross-sectional study (C) case-control study (D) historical cohort study (E) clinical treatment trial
(A) Case-controlled study The study described in the question stem is a case-controlled study. This type of study is then both observational and retrospective. In case-controlled studies the participants are identified based on the presence or absence of a particular outcome such as melanoma. Then the participants are asked about prior exposures. The data is analyzed by the odds ratio, which tells what the odds are that a person with a particular exposure will develop a particular disease.
Researchers are interested in identifying risk factors necessary for development of malignant melanoma. They enroll 10,000 people in the study, 3,000 of which have been diagnosed with melanoma and the remaining who serve as controls. Each participant fills out a detailed survey to identify any common risk factors in the patients with melanoma that are not present in control participants. Which of the following types of studies is described above? (A) Case-controlled study (B) Cohort study (C) Cross-sectional study (D) Double blind study (E) Meta-analysis
(B) Cohort study Cohort studies are observational and prospective. Participants are divided into groups based on exposure and then followed for development of the disease. In this case, the participants are divided based on the presence or absence of a first-degree relative who has been diagnosed with breast cancer. They are then followed for a period of 10 years to determine whether the participants develop breast cancer. The relative risk is the statistic used for identifying the increased risk for developing disease in people with a particular risk factor.
The public health department wants to know about the general health of a particular town. A survey is sent out to each person who lives in the town regarding their health. Only 43% people returned the survey. From this, it is estimated that 28% of the population has diabetes. Which of the following types of studies is described above? (A) Case-controlled study (B) Cohort study (C) Cross-sectional study (D) Double blind study (E) Meta-analysis
