Study designs

Study designs US Medical PG Question 1: A researcher is studying whether a new knee implant is better than existing alternatives in terms of pain after knee replacement. She designs the study so that it includes all the surgeries performed at a certain hospital. Interestingly, she notices that patients who underwent surgeries on Mondays and Thursdays reported much better pain outcomes on a survey compared with those who underwent the same surgeries from the same surgeons on Tuesdays and Fridays. Upon performing further analysis, she discovers that one of the staff members who works on Mondays and Thursdays is aware of the study and tells all the patients about how wonderful the new implant is. Which of the following forms of bias does this most likely represent?

• A. Hawthorne effect
• B. Pygmalion effect (Correct Answer)
• C. Attrition bias
• D. Golem effect

Study designs Explanation: ***Pygmalion effect*** - This bias occurs when higher expectations lead to an increase in performance. In this scenario, the staff member's positive reinforcement about the new implant likely instilled **higher patient expectations**, leading to better reported pain outcomes. - The patients' belief in the implant's superiority, influenced by the staff member, acted as a **self-fulfilling prophecy**, improving their subjective pain experience. *Hawthorne effect* - This effect describes how individuals modify an aspect of their behavior in response to their awareness of being observed. While patients were part of a study, their improved outcomes were specifically linked to a staff member's verbal influence, not solely the act of observation. - The improved pain outcomes stem from the **expectations created by the staff member's praise**, rather than a general awareness of being studied. *Attrition bias* - Attrition bias refers to systematic differences between groups in the loss of participants from a study. - This scenario describes differences in patient outcomes based on staff influence during the study, not due to **patients dropping out differentially** between groups. *Golem effect* - The Golem effect is the opposite of the Pygmalion effect, where lower expectations placed upon individuals lead to poorer performance from them. - In this case, the staff member's influence created **high expectations and positive outcomes**, not negative expectations leading to worse outcomes.

Study designs US Medical PG Question 2: A 42-year-old woman presents to the physician with symptoms of vague abdominal pain and bloating for several months. Test results indicate that she has ovarian cancer. Her physician attempts to reach her by phone multiple times but cannot reach her. Next of kin numbers are in her chart. According to HIPAA regulations, who should be the primary person the doctor discusses this information with?

• A. The patient's brother
• B. The patient's husband
• C. The patient's daughter
• D. All of the options
• E. The patient (Correct Answer)

Study designs Explanation: ***The patient*** - Under **HIPAA**, the patient has the **right to privacy** regarding their protected health information (PHI). Therefore, the physician must make all reasonable attempts to contact the patient directly to convey their diagnosis. - Sharing sensitive medical information like a cancer diagnosis with anyone other than the patient, without their explicit consent, would be a **violation of HIPAA regulations**. *The patient's brother* - The patient's brother is not automatically authorized to receive her medical information, even if listed as **next of kin**, without the patient's explicit consent or a documented **healthcare power of attorney**. - Discussing the diagnosis with the brother without the patient's direct consent would be a **breach of patient confidentiality**. *The patient's husband* - Even a spouse does not automatically have the right to access a patient's **PHI** without the patient's express permission, according to **HIPAA**. - While often a trusted contact, without explicit consent, revealing the diagnosis to the husband would still violate the patient's **privacy rights**. *The patient's daughter* - Similar to other family members, the patient's daughter is not legally entitled to receive her mother's confidential medical information without explicit authorization or a medical **power of attorney**. - The physician's primary responsibility is to the patient herself, ensuring her **privacy** is maintained. *All of the options* - According to **HIPAA**, sharing the patient's diagnosis with any family member without her explicit consent would be a **breach of confidentiality**. - This option incorrectly assumes that **next of kin** automatically have the right to receive sensitive medical information.

Study designs US Medical PG 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)

Study designs 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.

Study designs US Medical PG Question 4: A researcher is trying to determine whether a newly discovered substance X can be useful in promoting wound healing after surgery. She conducts this study by enrolling the next 100 patients that will be undergoing this surgery and separating them into 2 groups. She decides which patient will be in which group by using a random number generator. Subsequently, she prepares 1 set of syringes with the novel substance X and 1 set of syringes with a saline control. Both of these sets of syringes are unlabeled and the substances inside cannot be distinguished. She gives the surgeon performing the surgery 1 of the syringes and does not inform him nor the patient which syringe was used. After the study is complete, she analyzes all the data that was collected and performs statistical analysis. This study most likely provides which level of evidence for use of substance X?

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

Study designs Explanation: ***Level 1*** - The study design described is a **randomized controlled trial (RCT)**, which is considered the **highest level of evidence (Level 1)** in the hierarchy of medical evidence. - Key features like **randomization**, **control group**, and **blinding (double-blind)** help minimize bias and strengthen the validity of the findings. *Level 2* - Level 2 evidence typically comprises **well-designed controlled trials without randomization** (non-randomized controlled trials) or **high-quality cohort studies**. - While strong, they do not possess the same level of internal validity as randomized controlled trials. *Level 3* - Level 3 evidence typically includes **case-control studies** or **cohort studies**, which are observational designs and carry a higher risk of bias compared to RCTs. - These studies generally do not involve randomization or intervention assignment by the researchers. *Level 4* - Level 4 evidence is usually derived from **case series** or **poor quality cohort and case-control studies**. - These studies provide descriptive information or investigate associations without strong control for confounding factors. *Level 5* - Level 5 evidence is the **lowest level of evidence**, consisting of **expert opinion** or **animal research/bench research**. - This level lacks human clinical data or systematic investigative rigor needed for higher evidence levels.

Study designs US Medical PG Question 5: 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)

Study designs 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.

Study designs Flashcard 1 of 5

Question: Both twin concordance and adoption studies are useful for measuring '_____'

Answer: nature vs. nurture

Study designs Flashcard 2 of 5

Question: Which type of conditioning usually deals with voluntary responses? _____

Answer: Operant conditioning

Study designs Flashcard 3 of 5

Question: What percent of twins are monozygotic?

Answer: 20%

Study designs Flashcard 4 of 5

Question: What percent of twins are dizygotic?

Answer: 80%

Study designs Flashcard 5 of 5

Question: Explain how a twin concordance study works.

Answer: Compares the frequency with which twins (mono- or dizygotic) develop the same disease.