Allocation concealment — MCQs

10 questions

A senior medicine resident receives negative feedback on a grand rounds presentation from his attending. He is told sternly that he must improve his performance on the next project. Later that day, he yells at his medical student for not showing enough initiative, though he had voiced only satisfaction with the student's performance up until this point. Which of the following psychological defense mechanisms is he demonstrating?

A research team develops a new monoclonal antibody checkpoint inhibitor for advanced melanoma that has shown promise in animal studies as well as high efficacy and low toxicity in early phase human clinical trials. The research team would now like to compare this drug to existing standard of care immunotherapy for advanced melanoma. The research team decides to conduct a non-randomized study where the novel drug will be offered to patients who are deemed to be at risk for toxicity with the current standard of care immunotherapy, while patients without such risk factors will receive the standard treatment. Which of the following best describes the level of evidence that this study can offer?

A researcher is conducting a study to compare fracture risk in male patients above the age of 65 who received annual DEXA screening to peers who did not receive screening. He conducts a randomized controlled trial in 900 patients, with half of participants assigned to each experimental group. The researcher ultimately finds similar rates of fractures in the two groups. He then notices that he had forgotten to include 400 patients in his analysis. Including the additional participants in his analysis would most likely affect the study's results in which of the following ways?

A pharmaceutical corporation has asked you to assist in the development of a randomized controlled trial (RCT) to evaluate the response of renal cell carcinoma to a novel chemotherapeutic agent. Despite all of the benefits that an RCT has to offer, which of the following would make an RCT unacceptable with regard to study design?

An investigator is measuring the blood calcium level in a sample of female cross country runners and a control group of sedentary females. If she would like to compare the means of the two groups, which statistical test should she use?

A resident in the department of obstetrics and gynecology is reading about a randomized clinical trial from the late 1990s that was conducted to compare breast cancer mortality risk, disease localization, and tumor size in women who were randomized to groups receiving either annual mammograms starting at age 40 or annual mammograms starting at age 50. One of the tables in the study compares the two experimental groups with regard to socioeconomic demographics (e.g., age, income), medical conditions at the time of recruitment, and family history of breast cancer. The purpose of this table is most likely to evaluate which of the following?

An academic medical center in the United States is approached by a pharmaceutical company to run a small clinical trial to test the effectiveness of its new drug, compound X. The company wants to know if the measured hemoglobin a1c (Hba1c) of patients with type 2 diabetes receiving metformin and compound X would be lower than that of control subjects receiving only metformin. After a year of study and data analysis, researchers conclude that the control and treatment groups did not differ significantly in their Hba1c levels. However, parallel clinical trials in several other countries found that compound X led to a significant decrease in Hba1c. Interested in the discrepancy between these findings, the company funded a larger study in the United States, which confirmed that compound X decreased Hba1c levels. After compound X was approved by the FDA, and after several years of use in the general population, outcomes data confirmed that it effectively lowered Hba1c levels and increased overall survival. What term best describes the discrepant findings in the initial clinical trial run by institution A?

A resident doctor was reprimanded by the attending physician for making medication errors during morning rounds. Later that day, when a medical student asked a simple question about drug dosages during the evening rounds, the resident responded with excessive criticism and harsh comments, making the student visibly uncomfortable and embarrassed. Which of the following ego defense mechanisms is the resident demonstrating?

A study seeks to investigate the therapeutic efficacy of treating asymptomatic subclinical hypothyroidism in preventing symptoms of hypothyroidism. The investigators found 300 asymptomatic patients with subclinical hypothyroidism, defined as serum thyroid-stimulating hormone (TSH) of 5 to 10 μU/mL with normal serum thyroxine (T4) levels. The patients were randomized to either thyroxine 75 μg daily or placebo. Both investigators and study subjects were blinded. Baseline patient characteristics were distributed similarly in the treatment and control group (p > 0.05). Participants' serum T4 and TSH levels and subjective quality of life were evaluated at a 3-week follow-up. No difference was found between the treatment and placebo groups. Which of the following is the most likely explanation for the results of this study?

Q10

In the study, all participants who were enrolled and randomly assigned to treatment with pulmharkimab were analyzed in the pulmharkimab group regardless of medication nonadherence or refusal of allocated treatment. A medical student reading the abstract is confused about why some participants assigned to pulmharkimab who did not adhere to the regimen were still analyzed as part of the pulmharkimab group. Which of the following best reflects the purpose of such an analysis strategy?

Allocation concealment US Medical PG Practice Questions and MCQs

Question 1: A senior medicine resident receives negative feedback on a grand rounds presentation from his attending. He is told sternly that he must improve his performance on the next project. Later that day, he yells at his medical student for not showing enough initiative, though he had voiced only satisfaction with the student's performance up until this point. Which of the following psychological defense mechanisms is he demonstrating?

A. Transference
B. Projection
C. Countertransference
D. Externalization
E. Displacement (Correct Answer)

Explanation: ***Displacement*** - **Displacement** occurs when a person redirects an emotional response from a dangerous or threatening object to a safer, less threatening one. In this scenario, the resident, unable to express frustration towards his attending, redirects it onto the medical student. - The resident's anger and frustration stemmed from the negative feedback and stern reprimand from his attending; his subsequent yelling at the medical student despite prior satisfaction is a clear example of shifting these feelings to a less powerful target. *Transference* - **Transference** involves a patient unconsciously redirecting feelings and attitudes from important past relationships (e.g., parents) onto the therapist or other individuals in the present. - This scenario describes the resident's reaction to current stress, not the re-enactment of past relational patterns in a clinical setting. *Projection* - **Projection** is a defense mechanism where individuals attribute their own unacceptable thoughts, feelings, or impulses to another person. - The resident is not attributing his own perceived inadequacy or anger to the student; rather, he is expressing his anger *at* the student, which originated from a different source. *Countertransference* - **Countertransference** is a phenomenon in therapy where the therapist projects their own feelings onto the patient, often in response to the patient's transference. - This mechanism is specific to the therapeutic context and involves the therapist's emotional reactions, which is not applicable to the resident's general interaction with a medical student. *Externalization* - **Externalization** is a broad term referring to the tendency to blame outside factors for one's problems or failures, essentially viewing distress as coming from outside oneself. - While related to projection, externalization specifically focuses on attributing causality of one's struggles to external circumstances rather than a direct redirection of an emotional response to a different target. The resident isn't just blaming others for his problems; he is actively expressing displaced anger.

Question 2: A research team develops a new monoclonal antibody checkpoint inhibitor for advanced melanoma that has shown promise in animal studies as well as high efficacy and low toxicity in early phase human clinical trials. The research team would now like to compare this drug to existing standard of care immunotherapy for advanced melanoma. The research team decides to conduct a non-randomized study where the novel drug will be offered to patients who are deemed to be at risk for toxicity with the current standard of care immunotherapy, while patients without such risk factors will receive the standard treatment. Which of the following best describes the level of evidence that this study can offer?

A. Level 1
B. Level 3 (Correct Answer)
C. Level 5
D. Level 4
E. Level 2

Explanation: ***Level 3*** - A **non-randomized controlled trial** like the one described, where patient assignment to treatment groups is based on specific characteristics (risk of toxicity), falls into Level 3 evidence. - This level typically includes **non-randomized controlled trials** and **well-designed cohort studies** with comparison groups, which are prone to selection bias and confounding. - The study compares two treatments but lacks randomization, making it Level 3 evidence. *Level 1* - Level 1 evidence is the **highest level of evidence**, derived from **systematic reviews and meta-analyses** of multiple well-designed randomized controlled trials or large, high-quality randomized controlled trials. - The described study is explicitly stated as non-randomized, ruling out Level 1. *Level 2* - Level 2 evidence involves at least one **well-designed randomized controlled trial** (RCT) or **systematic reviews** of randomized trials. - The current study is *non-randomized*, which means it cannot be classified as Level 2 evidence, as randomization is a key criterion for this level. *Level 4* - Level 4 evidence includes **case series**, **case-control studies**, and **poorly designed cohort or case-control studies**. - While the study is non-randomized, it is a controlled comparative trial rather than a case series or retrospective case-control study, placing it at Level 3. *Level 5* - Level 5 evidence is the **lowest level of evidence**, typically consisting of **expert opinion** without explicit critical appraisal, or based on physiology, bench research, or animal studies. - While the drug was initially tested in animal studies, the current human comparative study offers a higher level of evidence than expert opinion or preclinical data.

Question 3: A researcher is conducting a study to compare fracture risk in male patients above the age of 65 who received annual DEXA screening to peers who did not receive screening. He conducts a randomized controlled trial in 900 patients, with half of participants assigned to each experimental group. The researcher ultimately finds similar rates of fractures in the two groups. He then notices that he had forgotten to include 400 patients in his analysis. Including the additional participants in his analysis would most likely affect the study's results in which of the following ways?

A. Wider confidence intervals of results
B. Increased probability of committing a type II error
C. Decreased significance level of results
D. Increased external validity of results
E. Increased probability of rejecting the null hypothesis when it is truly false (Correct Answer)

Explanation: ***Increased probability of rejecting the null hypothesis when it is truly false*** - Including more participants increases the **statistical power** of the study, making it more likely to detect a true effect if one exists. - A higher sample size provides a more precise estimate of the population parameters, leading to a greater ability to **reject a false null hypothesis**. *Wider confidence intervals of results* - A larger sample size generally leads to **narrower confidence intervals**, as it reduces the standard error of the estimate. - Narrower confidence intervals indicate **greater precision** in the estimation of the true population parameter. *Increased probability of committing a type II error* - A **Type II error** (false negative) occurs when a study fails to reject a false null hypothesis. - Increasing the sample size typically **reduces the probability of a Type II error** because it increases statistical power. *Decreased significance level of results* - The **significance level (alpha)** is a pre-determined threshold set by the researcher before the study begins, typically 0.05. - It is independent of sample size and represents the **acceptable probability of committing a Type I error** (false positive). *Increased external validity of results* - **External validity** refers to the generalizability of findings to other populations, settings, or times. - While a larger sample size can enhance the representativeness of the study population, external validity is primarily determined by the **sampling method** and the study's design context, not just sample size alone.

Question 4: A pharmaceutical corporation has asked you to assist in the development of a randomized controlled trial (RCT) to evaluate the response of renal cell carcinoma to a novel chemotherapeutic agent. Despite all of the benefits that an RCT has to offer, which of the following would make an RCT unacceptable with regard to study design?

A. Proper treatment response is very common
B. The treatment is not widespread in use
C. The treatment does not represent the best known option
D. The treatment is expensive
E. The treatment has a known, adverse outcome (Correct Answer)

Explanation: ***The treatment has a known, adverse outcome*** - If a treatment is already known to cause **significant harm** or an adverse outcome, it would be unethical to randomize patients to receive it, as this would expose them to unnecessary risk. - **Ethical considerations** are paramount in clinical trial design; exposing patients to a known harmful treatment violates the principle of non-maleficence. *Proper treatment response is very common* - A high treatment response rate would make it **easier to detect a difference** between the novel agent and a control group, potentially requiring a smaller sample size. - This scenario actually **facilitates** an RCT, as it increases the likelihood of demonstrating efficacy for the novel agent. *The treatment is not widespread in use* - The purpose of an RCT for a novel agent is precisely to evaluate its efficacy and safety to determine if it **deserves widespread use**. - Lack of widespread use is the **starting point** for clinical trials, not a contraindication. *The treatment does not represent the best known option* - An RCT is often conducted to determine if a novel treatment is **superior or non-inferior** to existing standard-of-care treatments, even if the existing options are not considered "the best." - Comparing a new treatment against a suboptimal current standard is a common and **valid objective** in clinical research to seek improvement. *The treatment is expensive* - The cost of a treatment is a **practical consideration** for healthcare systems and patients but does not inherently make an RCT unacceptable in terms of study design or ethics. - **Cost-effectiveness** is often evaluated after efficacy and safety are established, usually in addition to the RCT or in subsequent studies.

Question 5: An investigator is measuring the blood calcium level in a sample of female cross country runners and a control group of sedentary females. If she would like to compare the means of the two groups, which statistical test should she use?

A. Chi-square test
B. Linear regression
C. t-test (Correct Answer)
D. ANOVA (Analysis of Variance)
E. F-test

Explanation: ***t-test*** - A **t-test** is appropriate for comparing the means of two independent groups, such as the blood calcium levels between runners and sedentary females. - It assesses whether the observed difference between the two sample means is statistically significant or occurred by chance. *Chi-square test* - The **chi-square test** is used to analyze categorical data to determine if there is a significant association between two variables. - It is not suitable for comparing continuous variables like blood calcium levels. *Linear regression* - **Linear regression** is used to model the relationship between a dependent variable (outcome) and one or more independent variables (predictors). - It aims to predict the value of a variable based on the value of another, rather than comparing means between groups. *ANOVA (Analysis of Variance)* - **ANOVA** is used to compare the means of **three or more independent groups**. - Since there are only two groups being compared in this scenario, a t-test is more specific and appropriate. *F-test* - The **F-test** is primarily used to compare the variances of two populations or to assess the overall significance of a regression model. - While it is the basis for ANOVA, it is not the direct test for comparing the means of two groups.

Question 6: A resident in the department of obstetrics and gynecology is reading about a randomized clinical trial from the late 1990s that was conducted to compare breast cancer mortality risk, disease localization, and tumor size in women who were randomized to groups receiving either annual mammograms starting at age 40 or annual mammograms starting at age 50. One of the tables in the study compares the two experimental groups with regard to socioeconomic demographics (e.g., age, income), medical conditions at the time of recruitment, and family history of breast cancer. The purpose of this table is most likely to evaluate which of the following?

A. Observer bias
B. Statistical power
C. Confounding
D. Randomization (Correct Answer)
E. Effect modification

Explanation: ***Randomization*** - In a randomized clinical trial, the purpose of comparing baseline characteristics between experimental groups is to assess if **randomization successfully distributed potential confounders** evenly. - An even distribution of baseline characteristics suggests that any observed differences in outcomes are more likely due to the intervention rather than **pre-existing differences** between the groups. *Observer bias* - **Observer bias** occurs when researchers' expectations influence their observations or interpretation of results, which is not evaluated by comparing baseline demographics. - This type of bias is typically mitigated through **blinding** of researchers or participants, rather than checking baseline characteristics. *Statistical power* - **Statistical power** refers to the probability of correctly rejecting a false null hypothesis and detecting a true effect. - It is determined by factors like sample size and effect size, not by the **balance of baseline characteristics** between groups. *Effect modification* - **Effect modification** occurs when the effect of an exposure on an outcome varies across different levels of a third variable. - This is an **analytical consideration** explored in later stages of data analysis, not a concern addressed by comparing baseline characteristics. *Confounding* - **Confounding** occurs when an extraneous variable is associated with both the exposure and the outcome, distorting the true relationship. - While the baseline table helps verify that potential confounders are evenly distributed, the primary purpose is to evaluate whether **randomization was successful**, not to directly assess confounding as an analysis concern.

Question 7: An academic medical center in the United States is approached by a pharmaceutical company to run a small clinical trial to test the effectiveness of its new drug, compound X. The company wants to know if the measured hemoglobin a1c (Hba1c) of patients with type 2 diabetes receiving metformin and compound X would be lower than that of control subjects receiving only metformin. After a year of study and data analysis, researchers conclude that the control and treatment groups did not differ significantly in their Hba1c levels. However, parallel clinical trials in several other countries found that compound X led to a significant decrease in Hba1c. Interested in the discrepancy between these findings, the company funded a larger study in the United States, which confirmed that compound X decreased Hba1c levels. After compound X was approved by the FDA, and after several years of use in the general population, outcomes data confirmed that it effectively lowered Hba1c levels and increased overall survival. What term best describes the discrepant findings in the initial clinical trial run by institution A?

A. Type I error
B. Hawthorne effect
C. Type II error (Correct Answer)
D. Publication bias
E. Confirmation bias

Explanation: ***Type II error*** - A **Type II error** occurs when a study fails to **reject a false null hypothesis**, meaning it concludes there is no significant difference or effect when one actually exists. - In this case, the initial US trial incorrectly concluded that Compound X had no significant effect on HbA1c, while subsequent larger studies and real-world data proved it did. *Type I error* - A **Type I error** (alpha error) occurs when a study incorrectly **rejects a true null hypothesis**, concluding there is a significant difference or effect when there isn't. - This scenario describes the opposite: the initial study failed to find an effect that genuinely existed, indicating a Type II error, not a Type I error. *Hawthorne effect* - The **Hawthorne effect** is a type of reactivity in which individuals modify an aspect of their behavior in response to their awareness of being observed. - This effect does not explain the initial trial's failure to detect a real drug effect; rather, it relates to participants changing behavior due to study participation itself. *Publication bias* - **Publication bias** occurs when studies with positive or statistically significant results are more likely to be published than those with negative or non-significant results. - While relevant to the literature as a whole, it doesn't explain the discrepancy in findings within a single drug's development where a real effect was initially missed. *Confirmation bias* - **Confirmation bias** is the tendency to search for, interpret, favor, and recall information in a way that confirms one's preexisting beliefs or hypotheses. - This bias would likely lead researchers to *find* an effect if they expected one, or to disregard data that contradicts their beliefs, which is not what happened in the initial trial.

Question 8: A resident doctor was reprimanded by the attending physician for making medication errors during morning rounds. Later that day, when a medical student asked a simple question about drug dosages during the evening rounds, the resident responded with excessive criticism and harsh comments, making the student visibly uncomfortable and embarrassed. Which of the following ego defense mechanisms is the resident demonstrating?

A. Displacement (Correct Answer)
B. Reaction formation
C. Projection
D. Passive aggression
E. Acting out

Explanation: ***Displacement*** - **Displacement** involves redirecting unacceptable feelings and impulses from their original source to a safer, less threatening recipient. - The resident, unable to express anger towards the attending physician (a threatening figure), directs it at the medical student (a safer target). *Reaction formation* - **Reaction formation** is transforming an unacceptable impulse or feeling into its opposite. - This would involve the resident being overly kind or solicitous towards the medical student, rather than critical, to mask their underlying anger or insecurity. *Projection* - **Projection** involves attributing one's own unacceptable thoughts or feelings to someone else. - In this scenario, projection would mean the resident accusing the medical student of being incompetent or prone to errors, rather than simply criticizing them in response to prior reprimand. *Passive aggression* - **Passive aggression** is an indirect expression of hostility, often characterized by procrastination, stubbornness, intentional inefficiency, or forgotten commitments. - While the criticism was harsh, it was a direct expression of anger, not an indirect, subversive act. *Acting out* - **Acting out** involves expressing unconscious emotional conflicts or stressors through actions rather than words. - This mechanism typically involves impulsive behavior that could be harmful to oneself or others, which is not primarily what occurred with the verbal criticism.

Question 9: A study seeks to investigate the therapeutic efficacy of treating asymptomatic subclinical hypothyroidism in preventing symptoms of hypothyroidism. The investigators found 300 asymptomatic patients with subclinical hypothyroidism, defined as serum thyroid-stimulating hormone (TSH) of 5 to 10 μU/mL with normal serum thyroxine (T4) levels. The patients were randomized to either thyroxine 75 μg daily or placebo. Both investigators and study subjects were blinded. Baseline patient characteristics were distributed similarly in the treatment and control group (p > 0.05). Participants' serum T4 and TSH levels and subjective quality of life were evaluated at a 3-week follow-up. No difference was found between the treatment and placebo groups. Which of the following is the most likely explanation for the results of this study?

A. Observer effect
B. Berkson bias
C. Latency period (Correct Answer)
D. Confounding bias
E. Lead-time bias

Explanation: ***Latency period*** - A **latency period** refers to the time between exposure to a cause (e.g., treatment) and the manifestation of its effects (e.g., symptom improvement). The study's **3-week follow-up is too short** to observe the therapeutic benefits of thyroxine in subclinical hypothyroidism. - Levothyroxine (T4) has a **half-life of approximately 7 days**, and it typically takes **6-8 weeks or longer** for steady-state levels to be achieved and for clinical symptoms to improve. The slow onset of action for thyroid hormone replacement and the gradual nature of symptom resolution mean a longer observation period (typically 3-6 months) is needed to assess efficacy in hypothyroidism. - The null results likely reflect insufficient follow-up time rather than lack of treatment effect. *Observer effect* - The **observer effect**, or Hawthorne effect, occurs when subjects change their behavior because they know they are being observed. This study used **double-blinding** (both investigators and subjects), which effectively minimizes the observer effect. - The primary issue here is the lack of observed therapeutic effect due to timing, not a change in behavior due to observation. *Berkson bias* - **Berkson bias** is a form of selection bias that arises in case-control studies conducted in hospitals, where the probability of being admitted to the hospital can be affected by both exposure and disease. - This study is a **randomized controlled trial**, not a case-control study, and the selection of participants does not illustrate this specific bias. *Confounding bias* - **Confounding bias** occurs when an extraneous variable is associated with both the exposure and the outcome, distorting the observed relationship. The study states that **baseline patient characteristics were similarly distributed (p > 0.05)**, indicating successful randomization and minimization of confounding. - While confounding is a common concern in observational studies, the RCT design and reported baseline similarities make it unlikely to be the primary explanation for the null results compared to an insufficient follow-up period. *Lead-time bias* - **Lead-time bias** is a form of detection bias where early detection of a disease through screening appears to prolong survival, even if the treatment does not change the course of the disease. - This study is evaluating the **efficacy of treatment** in asymptomatic individuals with subclinical hypothyroidism, not the effect of screening on survival, making lead-time bias irrelevant to these results.

Question 10: In the study, all participants who were enrolled and randomly assigned to treatment with pulmharkimab were analyzed in the pulmharkimab group regardless of medication nonadherence or refusal of allocated treatment. A medical student reading the abstract is confused about why some participants assigned to pulmharkimab who did not adhere to the regimen were still analyzed as part of the pulmharkimab group. Which of the following best reflects the purpose of such an analysis strategy?

A. To minimize type 2 errors
B. To assess treatment efficacy more accurately
C. To reduce selection bias (Correct Answer)
D. To increase internal validity of study
E. To increase sample size

Explanation: ***To reduce selection bias*** - Analyzing participants in their originally assigned groups, regardless of adherence, is known as **intention-to-treat (ITT) analysis**. - This method helps **preserve randomization** and minimizes **selection bias** that could arise if participants who did not adhere to treatment were excluded or re-assigned. - **This is the most direct and specific purpose** of ITT analysis - preventing systematic differences between groups caused by post-randomization exclusions. *To minimize type 2 errors* - While ITT analysis affects statistical power, its primary purpose is not specifically to minimize **type 2 errors** (false negatives). - ITT analysis may sometimes *increase* the likelihood of a type 2 error by diluting the treatment effect due to non-adherence. *To assess treatment efficacy more accurately* - ITT analysis assesses the **effectiveness** of *assigning* a treatment in a real-world setting, rather than the pure biological **efficacy** of the treatment itself. - Efficacy is better assessed by a **per-protocol analysis**, which only includes compliant participants. - ITT provides a more **conservative** and **pragmatic** estimate of treatment effect. *To increase internal validity of study* - While ITT analysis does contribute to **internal validity** by maintaining randomization, this is a **broader, secondary benefit** rather than the primary purpose. - Internal validity encompasses many aspects of study design; ITT specifically addresses **post-randomization bias prevention**. - The more precise answer is that ITT reduces **selection bias**, which is one specific threat to internal validity. - Many other design features also contribute to internal validity (blinding, standardized protocols, etc.), making this option less specific. *To increase sample size* - ITT analysis includes all randomized participants, so it maintains the initial **sample size** that was randomized. - However, the primary purpose is to preserve the integrity of randomization and prevent bias, not simply to increase the number of participants in the final analysis.

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