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Chapter 14: Problem 52

Refer to a landmark study conducted in 1896 in Denmark by Dr. Johannes Fibiger, who went on to receive the Nobel Prize in Medicine in \(1926 .\) The purpose of the study was to determine the effectiveness of a new serum for treating diphtheria, a common and often deadly respiratory disease in those days. Fibiger conducted his study over a one-year period (May 1896-April 1897) in one particular Copenhagen hospital. New diphtheria patients admitted to the hospital received different treatments based on the day of admission. In one set of days (call them "even" days for convenience), the patients were treated with the new serum daily and received the standard treatment. Patients admitted on alternate days (the "odd" days) received just the standard treatment. Over the one-year period of the study, eight of the 239 patients admitted on the "even" days and treated with the serum died, whereas 30 of the 245 patients admitted on the "odd" days died. In a different study on the effectiveness of the diphtheria serum conducted prior to Fibiger's study, patients in one Copenhagen hospital were chosen to be in the treatment group and were given the new serum, whereas patients in a different Copenhagen hospital were chosen to be in the control group and were given the standard treatment. Fibiger did not believe that the results of this earlier study could be trusted. What are some possible confounding variables that may have affected the results of this earlier study?

Short Answer

Expert verified
There could have been numerous confounding variables in the previous study. These include differences in the quality of care between the hospitals, differences in the patient demographic or severity of the disease, varying medical practitioner skill levels, differing facility and equipment standards. Furthermore, the timing of the treatment administration could have varied.

Step by step solution

01

Identify the treatment groups and control groups

Dr. Fibiger conducted an experiment where he divided patients based on the days they were admitted to the hospital. Patients admitted on even days were given the new serum treatment, and patients admitted on odd days were given the standard treatment. In a previous study, patients in one hospital were chosen to be the treatment group, who were given the new serum, while patients in a different hospital were chosen to be the control group, who were given the standard treatment.
02

Understand the issue with the previous study

The issue with the previous study, as observed by Dr. Fibiger, was that the treatment and control groups were in different hospitals. This design makes the experiment susceptible to confounding variables, as the two hospitals may not have the same conditions, equipments, staffing, among other factors.
03

Identify potential confounding variables

There are several potential confounding variables in this setup. Some of these could be: 1. Differences in the quality of care, facilities, skill level of the medical practitioners, or patient demographic between the hospitals. 2. There may exist differences in the severity of the patients' conditions in the two hospitals. 3. The timing of the treatment (whether it was administered at the same disease stage to all patients) may also have varied between the two hospitals.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Confounding Variables
In medical research, confounding variables are factors that can distort the outcome of an experiment if not properly controlled. These variables can be anything that might affect the dependent variable other than the independent variable being studied. For example, a confounding variable can be a patient's age affecting their response to treatment. This makes it difficult to determine whether the effect on the dependent variable is truly from the treatment or from the confounding factor.
  • **External Factors**: Such as environment or economic conditions that may differ between study locations.
  • **Demographic Differences**: Variables like a patient鈥檚 gender, age, and health condition that can vary across study groups.
  • **Medical Practices**: Differences in hospital equipment or staff skill levels that could influence the study outcomes.
Addressing confounding variables involves designing studies that keep these factors constant across treatment and control groups.
Experimental Treatment Group
The Experimental Treatment Group in a medical study refers to the participants who receive the treatment being tested. In Dr. Fibiger's study, for instance, the experimental group consisted of patients who received the new serum for treating diphtheria. When designing a study, it's essential to carefully select the experimental group to ensure that the treatment's effects are accurately measured.
  • **Assignment**: Participants can be assigned to this group via random allocation or specific criteria that are controlled within the study.
  • **Measurement**: It's crucial to measure and record their outcomes using standardized methods to evaluate the treatment's effectiveness.
Ensuring the experimental group is comparable to the control group in all aspects except the treatment administered is vital for drawing valid conclusions.
Control Group
The Control Group is a critical component in medical study design. It consists of participants who do not receive the experimental treatment but instead receive a standard treatment or placebo. This group's role is to serve as a benchmark for measuring the treatment effect.
  • **Purpose**: By comparing outcomes in the control group to those in the experimental group, researchers can determine whether the treatment has a significant impact.
  • **Consistency**: It鈥檚 essential that the control group be similar to the experimental group in every way except the treatment to ensure that any differences in outcomes are due to the treatment.
Errors in selecting or managing a control group can lead to ambiguous or inaccurate study results.
Historical Medical Research
The field of Historical Medical Research refers to the study of historical data, trials, and discoveries in medicine. Looking at historical studies, like the one conducted by Dr. Fibiger, provides insights into how medical knowledge has evolved over time. Dr. Fibiger's study was innovative for its time as it introduced a more systematic method for evaluating medical treatments.
  • **Lessons Learned**: History tells us about the progression from rudimentary to more sophisticated medical study designs.
  • **Methodologies**: Understanding past methodologies can highlight both successes and pitfalls that modern scientists can learn from.
The design of Fibiger's study, using separate experimental and control groups within the same hospital, minimized confounding variables, making the results more reliable and marking a significant progress in clinical research at the time.

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Most popular questions from this chapter

The Dean of Students at Tasmania State University wants to determine how many undergraduates at TSU are familiar with a new financial aid program offered by the university. There are 15,000 undergraduates at TSU, so it is too expensive to conduct a census. Instead, the dean decides to conduct a survey using a sample of 150 undergraduates. Describe how the dean might implement each of the following sampling methods. (See also Exercises 57 through \(60 .\) ) (a) Simple random sampling (b) Convenience sampling (c) Stratified sampling (d) Quota sampling

A large jar contains an unknown number of red gumballs and 150 green gumballs. As part of a seventh-grade class project the teacher asks Carlos to estimate the total number of gumballs in the jar using a sample. Carlos draws a sample of 50 gumballs, of which 19 are red and 31 are green. Use Carlos' sample to estimate the number of gumballs in the jar.

Refer to a clinical study conducted at the Houston Veterans Administration Medical Center on the effectiveness of knee surgery to cure degenerative arthritis (osteoarthritis) of the knee. Of the 324 individuals who met the inclusion criteria for the study, 144 declined to participate. The researchers randomly divided the remaining 180 subjects into three groups: One group received a type of arthroscopic knee surgery called debridement; a second group received a type of arthroscopic knee surgery called lavage; and a third group received skin incisions to make it look like they had had arthroscopic knee surgery, but no actual surgery was performed. The patients in the study did not know which group they were in and in particular did not know if they were receiving the real surgery or simulated surgery. All the patients who participated in the study were evaluated for two years after the procedure. In the two-year follow-up, all three groups said that they had slightly less pain and better knee movement, but the "fake" surgery group often reported the best results. (a) Describe as specifically as you can the target population for this study. (b) Describe the sample.

Refer to a study on the effectiveness of an HPV (human papilloma virus) vaccine conducted between October 1998 and November \(1999 .\) HPV is the most common sexually transmitted infection-more than 20 million Americans are infected with HPV-but most HPV infections are benign, and in most cases infected individuals are not even aware they are infected. (On the other hand, some HPV infections can lead to cervical cancer in women.) The researchers recruited 2392 women from 16 different centers across the United States to participate in the study through advertisements on college campuses and in the surrounding communities. To be eligible to participate in the study, the subjects had to meet the following criteria: (1) be a female between 16 and 23 years of age, (2) not be pregnant, (3) have no prior abnormal Pap smears, and (4) report to have had sexual relations with no more than five men. At each center, half of the participants were randomly selected to receive the HPV vaccine, and the other half received a placebo injection. After 17.4 months, the incidence of HPV infection was 3.8 per 100 woman-years at risk in the placebo group and 0 per 100 woman-years at risk in the vaccine group. In addition, all nine cases of HPV-related cervical precancerous growths occurred among the placebo recipients. (a) Describe the treatment group in the study. (b) Could this study be considered a double-blind, randomized controlled placebo study? Explain.

Refer to a study on the effectiveness of an HPV (human papilloma virus) vaccine conducted between October 1998 and November \(1999 .\) HPV is the most common sexually transmitted infection-more than 20 million Americans are infected with HPV-but most HPV infections are benign, and in most cases infected individuals are not even aware they are infected. (On the other hand, some HPV infections can lead to cervical cancer in women.) The researchers recruited 2392 women from 16 different centers across the United States to participate in the study through advertisements on college campuses and in the surrounding communities. To be eligible to participate in the study, the subjects had to meet the following criteria: (1) be a female between 16 and 23 years of age, (2) not be pregnant, (3) have no prior abnormal Pap smears, and (4) report to have had sexual relations with no more than five men. At each center, half of the participants were randomly selected to receive the HPV vaccine, and the other half received a placebo injection. After 17.4 months, the incidence of HPV infection was 3.8 per 100 woman-years at risk in the placebo group and 0 per 100 woman-years at risk in the vaccine group. In addition, all nine cases of HPV-related cervical precancerous growths occurred among the placebo recipients. (a) Describe the sample for the study. (b) Was the sample chosen using random sampling? Explain.
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