Principles and design of RCTs US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Principles and design of RCTs. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Principles and design of RCTs US Medical PG Question 1: A 21-year-old man presents to the office for a follow-up visit. He was recently diagnosed with type 1 diabetes mellitus after being hospitalized for diabetic ketoacidosis following a respiratory infection. He is here today to discuss treatment options available for his condition. The doctor mentions a recent study in which researchers have developed a new version of the insulin pump that appears efficacious in type 1 diabetics. They are currently comparing it to insulin injection therapy. This new pump is not yet available, but it looks very promising. At what stage of clinical trials is this current treatment most likely at?
- A. Phase 0
- B. Phase 2
- C. Phase 3 (Correct Answer)
- D. Phase 1
- E. Phase 4
Principles and design of RCTs Explanation: ***Phase 3***
- **Phase 3 trials** involve large-scale studies comparing the new treatment to standard therapy or placebo, often across multiple centers.
- The scenario describes a "new version of the insulin pump" being compared to "insulin injection therapy," indicating a definitive comparison for efficacy and safety against existing treatments.
*Phase 0*
- **Phase 0 trials** are exploratory, small-scale studies (10-15 subjects) using micro-doses to gather preliminary data on pharmacodynamics and pharmacokinetics, not efficacy comparisons.
- They are typically conducted very early in drug development, examining if the drug behaves as expected in humans.
*Phase 2*
- **Phase 2 trials** evaluate the efficacy and further assess safety of a new treatment in a larger group of patients (tens to hundreds).
- While they assess efficacy, they usually don't involve direct comparison with an established standard therapy on the scale implied by the question, which is typically reserved for Phase 3.
*Phase 1*
- **Phase 1 trials** primarily focus on safety, dosage, and side effects in a small group of healthy volunteers or patients with the condition (20-100 subjects).
- These trials are not designed to assess a treatment's efficacy against an existing therapy.
*Phase 4*
- **Phase 4 trials** occur after a drug or device has been approved and marketed, focusing on long-term safety, effectiveness in diverse populations, and new indications.
- The described pump "is not yet available," indicating it has not reached the market and thus is not in Phase 4.
Principles and design of RCTs US Medical PG Question 2: 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)
Principles and design of RCTs 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.
Principles and design of RCTs US Medical PG Question 3: 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
Principles and design of RCTs 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.
Principles and design of RCTs US Medical PG Question 4: An experimental new drug (SD27C) is being studied. This novel drug delivers insulin via the intranasal route. Consent is obtained from participants who are diabetic and are taking insulin as their current treatment regimen to participate in a clinical trial. 500 patients consent and are divided into 2 groups, and a double-blind clinical trial was conducted. One group received the new formulation (SD27C), while the second group received regular insulin via subcutaneous injection. The results showed that the treatment outcomes in both groups are the same. SD27C is currently under investigation in which phase of the clinical trial?
- A. Phase II
- B. Phase III (Correct Answer)
- C. Post-market surveillance
- D. Phase I
- E. Phase IV
Principles and design of RCTs Explanation: ***Phase III***
- **Phase III trials** involve a large number of participants (hundreds to thousands) and compare the new drug to standard treatment or placebo to assess its **efficacy** and monitor for adverse effects.
- The description of a **double-blind clinical trial** with 500 patients divided into two groups, comparing the new drug (SD27C) to regular insulin with similar treatment outcomes, is characteristic of a Phase III study.
*Phase II*
- **Phase II trials** typically involve a smaller group of patients (tens to a few hundred) to evaluate the drug's **effectiveness**, further assess safety, and determine the optimal dosage.
- The sample size of 500 patients in this scenario is too large for a typical Phase II trial.
*Post-market surveillance*
- This term is synonymous with **Phase IV trials**, which occur after the drug has been approved and marketed, focusing on long-term safety and effectiveness in a broader population.
- The drug is still "under investigation" and being compared to existing treatment, indicating it has not yet been approved.
*Phase I*
- **Phase I trials** are the initial human trials, usually involving a small number of **healthy volunteers**, to evaluate the drug's safety, dosage range, and pharmacokinetics.
- The study involves diabetic patients, not healthy volunteers, and the focus is on efficacy comparison, not just basic safety.
*Phase IV*
- **Phase IV trials** (or post-market surveillance) take place **after a drug has been approved** and marketed, monitoring its long-term effects, optimal use, and safety in a real-world setting.
- The drug is still in a comparative efficacy trial and has not yet received approval for general use.
Principles and design of RCTs US Medical PG Question 5: 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
Principles and design of RCTs 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.
Principles and design of RCTs US Medical PG Question 6: A 57-year-old man presents to his oncologist to discuss management of small cell lung cancer. The patient is a lifelong smoker and was diagnosed with cancer 1 week ago. The patient states that the cancer was his fault for smoking and that there is "no hope now." He seems disinterested in discussing the treatment options and making a plan for treatment and followup. The patient says "he does not want any treatment" for his condition. Which of the following is the most appropriate response from the physician?
- A. "You seem upset at the news of this diagnosis. I want you to go home and discuss this with your loved ones and come back when you feel ready to make a plan together for your care."
- B. "It must be tough having received this diagnosis; however, new cancer therapies show increased efficacy and excellent outcomes."
- C. "It must be very challenging having received this diagnosis. I want to work with you to create a plan." (Correct Answer)
- D. "We are going to need to treat your lung cancer. I am here to help you throughout the process."
- E. "I respect your decision and we will not administer any treatment. Let me know if I can help in any way."
Principles and design of RCTs Explanation: ***"It must be very challenging having received this diagnosis. I want to work with you to create a plan."***
- This response **acknowledges the patient's emotional distress** and feelings of guilt and hopelessness, which is crucial for building rapport and trust.
- It also gently **re-engages the patient** by offering a collaborative approach to treatment, demonstrating the physician's commitment to supporting him through the process.
*"You seem upset at the news of this diagnosis. I want you to go home and discuss this with your loved ones and come back when you feel ready to make a plan together for your care."*
- While acknowledging distress, sending the patient home without further engagement **delays urgent care** for small cell lung cancer, which is aggressive.
- This response might be perceived as dismissive of his immediate feelings and can **exacerbate his sense of hopelessness** and isolation.
*"It must be tough having received this diagnosis; however, new cancer therapies show increased efficacy and excellent outcomes."*
- This statement moves too quickly to treatment efficacy without adequately addressing the patient's current **emotional state and fatalism**.
- While factual, it **lacks empathy** for his personal feelings of blame and hopelessness, potentially making him feel unheard.
*"We are going to need to treat your lung cancer. I am here to help you throughout the process."*
- This response is **too directive and authoritarian**, which can alienate a patient who is already feeling guilty and resistant to treatment.
- It fails to acknowledge his stated feelings of "no hope now" or his disinterest in treatment, which are critical to address before discussing the necessity of treatment.
*"I respect your decision and we will not administer any treatment. Let me know if I can help in any way."*
- While respecting patient autonomy is vital, immediately accepting a patient's decision to refuse treatment without exploring the underlying reasons (e.g., guilt, hopelessness, lack of information) is **premature and potentially harmful**.
- The physician has a responsibility to ensure the patient is making an informed decision, especially for a rapidly progressing condition like small cell lung cancer.
Principles and design of RCTs US Medical PG Question 7: You are currently employed as a clinical researcher working on clinical trials of a new drug to be used for the treatment of Parkinson's disease. Currently, you have already determined the safe clinical dose of the drug in a healthy patient. You are in the phase of drug development where the drug is studied in patients with the target disease to determine its efficacy. Which of the following phases is this new drug currently in?
- A. Phase 4
- B. Phase 1
- C. Phase 2 (Correct Answer)
- D. Phase 0
- E. Phase 3
Principles and design of RCTs Explanation: ***Phase 2***
- **Phase 2 trials** involve studying the drug in patients with the target disease to assess its **efficacy** and further evaluate safety, typically involving a few hundred patients.
- The question describes a stage after safe dosing in healthy patients (Phase 1) and before large-scale efficacy confirmation (Phase 3), focusing on efficacy in the target population.
*Phase 4*
- **Phase 4 trials** occur **after a drug has been approved** and marketed, monitoring long-term effects, optimal use, and rare side effects in a diverse patient population.
- This phase is conducted post-market approval, whereas the question describes a drug still in development prior to approval.
*Phase 1*
- **Phase 1 trials** primarily focus on determining the **safety and dosage** of a new drug in a **small group of healthy volunteers** (or sometimes patients with advanced disease if the drug is highly toxic).
- The question states that the safe clinical dose in a healthy patient has already been determined, indicating that Phase 1 has been completed.
*Phase 0*
- **Phase 0 trials** are exploratory, very early-stage studies designed to confirm that the drug reaches the target and acts as intended, typically involving a very small number of doses and participants.
- These trials are conducted much earlier in the development process, preceding the determination of safe clinical doses and large-scale efficacy studies.
*Phase 3*
- **Phase 3 trials** are large-scale studies involving hundreds to thousands of patients to confirm **efficacy**, monitor side effects, compare it to commonly used treatments, and collect information that will allow the drug to be used safely.
- While Phase 3 does assess efficacy, it follows Phase 2 and is typically conducted on a much larger scale before submitting for regulatory approval.
Principles and design of RCTs US Medical PG Question 8: A pharmaceutical company conducts a randomized clinical trial in an attempt to show that their new anticoagulant drug prevents more thrombotic events following total knee arthroplasty than the current standard of care. However, a significant number of patients are lost to follow-up or fail to complete treatment according to the study arm to which they were assigned. Several patients in the novel drug arm are also switched at a later time to a novel anticoagulant or warfarin per their primary care physician. All patients enrolled in the study are subsequently analyzed based on the initial group they were assigned to and there is a significant improvement in outcome of the new drug. What analysis most appropriately describes this trial?
- A. Per protocol
- B. As treated
- C. Non-inferiority
- D. Intention to treat (Correct Answer)
- E. Modified intention to treat
Principles and design of RCTs Explanation: ***Intention to treat***
- **Intention-to-treat (ITT)** analysis includes all participants randomized to a treatment arm, regardless of whether they completed the intervention or switched treatments, reflecting a real-world scenario and preserving randomization benefits.
- This approach minimizes bias from **loss to follow-up** or **treatment crossovers** and provides a more conservative estimate of treatment effect.
*Per protocol*
- **Per-protocol analysis** only includes participants who completed the study exactly as planned without any deviations.
- This method is susceptible to **selection bias** because it excludes patients who may have experienced adverse events or treatment failures, potentially overestimating treatment efficacy.
*As treated*
- **As-treated analysis** analyzes patients based on the actual treatment received, rather than the treatment to which they were randomized.
- This approach can introduce **confounding** and selection bias, as patients who switch treatments may do so for reasons related to their prognosis or treatment response.
*Non-inferiority*
- A **non-inferiority trial** design aims to show that a new treatment is not appreciably worse than an active control, rather than proving superiority.
- This describes a **type of study design** or hypothesis, not an analysis method for handling patient data after randomization with non-adherence.
*Modified intention to treat*
- A **modified intention-to-treat (mITT)** analysis typically excludes a small, predefined group of patients from the ITT population, such as those who never received any study drug or were found to be ineligible after randomization.
- While similar to ITT, it involves specific exclusions that are not described in this scenario, where all randomized patients were analyzed **based on initial assignment**.
Principles and design of RCTs US Medical PG 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
Principles and design of RCTs 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.
Principles and design of RCTs US Medical PG 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
Principles and design of RCTs 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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