Relationship with relative risk reduction — MCQs

10 questions

Group of 100 medical students took an end of the year exam. The mean score on the exam was 70%, with a standard deviation of 25%. The professor states that a student's score must be within the 95% confidence interval of the mean to pass the exam. Which of the following is the minimum score a student can have to pass the exam?

You are reading through a recent article that reports significant decreases in all-cause mortality for patients with malignant melanoma following treatment with a novel biological infusion. Which of the following choices refers to the probability that a study will find a statistically significant difference when one truly does exist?

A research group wants to assess the safety and toxicity profile of a new drug. A clinical trial is conducted with 20 volunteers to estimate the maximum tolerated dose and monitor the apparent toxicity of the drug. The study design is best described as which of the following phases of a clinical trial?

A research consortium is studying a new vaccine for respiratory syncytial virus (RSV) in premature infants compared to the current standard of care. 1000 infants were randomized to either the new vaccine group or the standard of care group. In total, 520 receive the new vaccine and 480 receive the standard of care. Of those who receive the new vaccine, 13 contract RSV. Of those who received the standard of care, 30 contract RSV. Which of the following is the absolute risk reduction of this new vaccine?

A survey was conducted in a US midwestern town in an effort to assess maternal mortality over the past year. The data from the survey are given in the table below: Women of childbearing age 250,000 Maternal deaths 2,500 Number of live births 100, 000 Number of deaths of women of childbearing age 7,500 Maternal death is defined as the death of a woman while pregnant or within 42 days of termination of pregnancy from any cause related to or aggravated by, the pregnancy. Which of the following is the maternal mortality rate in this midwestern town?

In a randomized controlled trial studying a new treatment, the primary endpoint (mortality) occurred in 14.4% of the treatment group and 16.7% of the control group. Which of the following represents the number of patients needed to treat to save one life, based on the primary endpoint?

A research team is working on a new assay meant to increase the sensitivity of testing in cervical cancer. Current sensitivity is listed at 77%. If this research team's latest work culminates in the following results (listed in the table), has the sensitivity improved, and, if so, then by what percentage? Research team's latest results: | | Patients with cervical cancer | Patients without cervical cancer | |--------------------------|-------------------------------|----------------------------------| | Test is Positive (+) | 47 | 4 | | Test is Negative (-) | 9 | 44 |

A randomized controlled trial was initiated to evaluate a novel DPP-4 inhibitor for blood glucose management in diabetic patients. The study used a commonly prescribed sulfonylurea as the standard of care treatment. 2,000 patients were enrolled in the study with 1,000 patients in each arm. One of the primary outcomes was the development of diabetic nephropathy during treatment. This outcome occurred in 68 patients on the DPP-4 inhibitor and 134 patients on the sulfonylurea. What is the relative risk reduction (RRR) for patients using the DPP-4 inhibitor compared with the sulfonylurea?

A medical research study is evaluating an investigational novel drug (medication 1) as compared with standard therapy (medication 2) in patients presenting to the emergency department with myocardial infarction (MI). The study enrolled a total of 3,000 subjects, 1,500 in each study arm. Follow-up was conducted at 45 days post-MI. The following are the results of the trial: Endpoints Medication 1 Medication 2 P-Value Primary: death from cardiac causes 134 210 0.03 Secondary: hyperkalemia 57 70 0.4 What is the relative risk of death from a cardiac cause, expressed as a percentage? (Round to the nearest whole number.)

Q10

A first time mother of a healthy, full term, newborn girl is anxious about sudden infant death syndrome. Which of the following pieces of advice can reduce the risk of SIDS?

Relationship with relative risk reduction US Medical PG Practice Questions and MCQs

Question 1: Group of 100 medical students took an end of the year exam. The mean score on the exam was 70%, with a standard deviation of 25%. The professor states that a student's score must be within the 95% confidence interval of the mean to pass the exam. Which of the following is the minimum score a student can have to pass the exam?

A. 45%
B. 63.75%
C. 67.5%
D. 20%
E. 65% (Correct Answer)

Explanation: ***65%*** - To find the **95% confidence interval (CI) of the mean**, we use the formula: Mean ± (Z-score × Standard Error). For a 95% CI, the Z-score is approximately **1.96**. - The **Standard Error (SE)** is calculated as SD/√n, where n is the sample size (100 students). So, SE = 25%/√100 = 25%/10 = **2.5%**. - The 95% CI is 70% ± (1.96 × 2.5%) = 70% ± 4.9%. The lower bound is 70% - 4.9% = **65.1%**, which rounds to **65%** as the minimum passing score. *45%* - This value is significantly lower than the calculated lower bound of the 95% confidence interval (approximately 65.1%). - It would represent a score far outside the defined passing range. *63.75%* - This value falls below the calculated lower bound of the 95% confidence interval (approximately 65.1%). - While close, this score would not meet the professor's criterion for passing. *67.5%* - This value is within the 95% confidence interval (65.1% to 74.9%) but is **not the minimum score**. - Lower scores within the interval would still qualify as passing. *20%* - This score is extremely low and falls significantly outside the 95% confidence interval for a mean of 70%. - It would indicate performance far below the defined passing threshold.

Question 2: You are reading through a recent article that reports significant decreases in all-cause mortality for patients with malignant melanoma following treatment with a novel biological infusion. Which of the following choices refers to the probability that a study will find a statistically significant difference when one truly does exist?

A. Type II error
B. Type I error
C. Confidence interval
D. p-value
E. Power (Correct Answer)

Explanation: ***Power*** - **Power** is the probability that a study will correctly reject the null hypothesis when it is, in fact, false (i.e., will find a statistically significant difference when one truly exists). - A study with high power minimizes the risk of a **Type II error** (failing to detect a real effect). *Type II error* - A **Type II error** (or **beta error**) occurs when a study fails to reject a false null hypothesis, meaning it concludes there is no significant difference when one actually exists. - This is the **opposite** of what the question describes, which asks for the probability of *finding* a difference. *Type I error* - A **Type I error** (or **alpha error**) occurs when a study incorrectly rejects a true null hypothesis, concluding there is a significant difference when one does not actually exist. - This relates to the **p-value** and the level of statistical significance (e.g., p < 0.05). *Confidence interval* - A **confidence interval** provides a range of values within which the true population parameter is likely to lie with a certain degree of confidence (e.g., 95%). - It does not directly represent the probability of finding a statistically significant difference when one truly exists. *p-value* - The **p-value** is the probability of observing data as extreme as, or more extreme than, that obtained in the study, assuming the null hypothesis is true. - It is used to determine statistical significance, but it is not the probability of detecting a true effect.

Question 3: A research group wants to assess the safety and toxicity profile of a new drug. A clinical trial is conducted with 20 volunteers to estimate the maximum tolerated dose and monitor the apparent toxicity of the drug. The study design is best described as which of the following phases of a clinical trial?

A. Phase 0
B. Phase III
C. Phase V
D. Phase II
E. Phase I (Correct Answer)

Explanation: ***Phase I*** - **Phase I clinical trials** involve a small group of healthy volunteers (typically 20-100) to primarily assess **drug safety**, determine a safe dosage range, and identify side effects. - The main goal is to establish the **maximum tolerated dose (MTD)** and evaluate the drug's pharmacokinetic and pharmacodynamic profiles. *Phase 0* - **Phase 0 trials** are exploratory studies conducted in a very small number of subjects (10-15) to gather preliminary data on a drug's **pharmacodynamics and pharmacokinetics** in humans. - They involve microdoses, not intended to have therapeutic effects, and thus cannot determine toxicity or MTD. *Phase III* - **Phase III trials** are large-scale studies involving hundreds to thousands of patients to confirm the drug's **efficacy**, monitor side effects, compare it to standard treatments, and collect information that will allow the drug to be used safely. - These trials are conducted after safety and initial efficacy have been established in earlier phases. *Phase V* - "Phase V" is not a standard, recognized phase in the traditional clinical trial classification (Phase 0, I, II, III, IV). - This term might be used in some non-standard research contexts or for post-marketing studies that go beyond Phase IV surveillance, but it is not a formal phase for initial drug development. *Phase II* - **Phase II trials** involve several hundred patients with the condition the drug is intended to treat, focusing on **drug efficacy** and further evaluating safety. - While safety is still monitored, the primary objective shifts to determining if the drug works for its intended purpose and at what dose.

Question 4: A research consortium is studying a new vaccine for respiratory syncytial virus (RSV) in premature infants compared to the current standard of care. 1000 infants were randomized to either the new vaccine group or the standard of care group. In total, 520 receive the new vaccine and 480 receive the standard of care. Of those who receive the new vaccine, 13 contract RSV. Of those who received the standard of care, 30 contract RSV. Which of the following is the absolute risk reduction of this new vaccine?

A. 4.3%
B. 3.75% (Correct Answer)
C. 6.25%
D. 1.7%
E. 2.5%

Explanation: ***3.75%*** - **Absolute Risk Reduction (ARR)** is calculated as the difference between the event rate in the control group (CER) and the event rate in the experimental group (EER). - Here, the event rate in the standard of care (control) group is (30/480) * 100% = 6.25%, and in the new vaccine (experimental) group is (13/520) * 100% = 2.5%. Therefore, ARR = 6.25% - 2.5% = **3.75%**. *4.3%* - This value might be obtained from an incorrect calculation or misinterpreting the numbers for the **risk reduction**. - It does not represent the direct difference in risk between the two groups. *6.25%* - This value represents the event rate in the **standard of care (control) group** (30/480). - It is the control event rate (CER), not the absolute risk reduction. *1.7%* - This value is not derived from the correct formula for **absolute risk reduction**. - It may arise from an incomplete or incorrect calculation of the risk difference. *2.5%* - This value represents the event rate in the **new vaccine (experimental) group** (13/520). - This is the experimental event rate (EER), not the absolute risk reduction.

Question 5: A survey was conducted in a US midwestern town in an effort to assess maternal mortality over the past year. The data from the survey are given in the table below: Women of childbearing age 250,000 Maternal deaths 2,500 Number of live births 100, 000 Number of deaths of women of childbearing age 7,500 Maternal death is defined as the death of a woman while pregnant or within 42 days of termination of pregnancy from any cause related to or aggravated by, the pregnancy. Which of the following is the maternal mortality rate in this midwestern town?

A. 1,000 per 100,000 live births
B. 33 per 100,000 live births
C. 3,000 per 100,000 live births
D. 33,300 per 100,000 live births
E. 2,500 per 100,000 live births (Correct Answer)

Explanation: ***2,500 per 100,000 live births*** - The maternal mortality rate is calculated as the number of **maternal deaths** per 100,000 **live births**. The given data directly provide these values. - Calculation: (2,500 maternal deaths / 100,000 live births) × 100,000 = **2,500 per 100,000 live births**. *1,000 per 100,000 live births* - This value is incorrect as it does not align with the provided numbers for maternal deaths and live births in the calculation. - It might result from a miscalculation or using incorrect numerator/denominator values from the dataset. *33 per 100,000 live births* - This value is significantly lower than the correct rate and suggests a substantial error in calculation or an incorrect understanding of how the maternal mortality rate is derived. - It could potentially result from dividing the number of live births by maternal deaths, which is the inverse of the correct formula. *3,000 per 100,000 live births* - This option is close to the correct answer but slightly higher, indicating a possible calculation error, for instance, including non-maternal deaths or other causes of deaths in the numerator. - The definition of maternal death is specific to pregnancy-related or aggravated causes, so extraneous deaths would inflate the rate. *33,300 per 100,000 live births* - This figure results from incorrectly calculating the proportion of maternal deaths among all deaths of women of childbearing age: (2,500 / 7,500) × 100,000 = 33,333. - This is a conceptual error as the maternal mortality rate should use live births as the denominator, not total deaths of women of childbearing age.

Question 6: In a randomized controlled trial studying a new treatment, the primary endpoint (mortality) occurred in 14.4% of the treatment group and 16.7% of the control group. Which of the following represents the number of patients needed to treat to save one life, based on the primary endpoint?

A. 1/(0.144 - 0.167)
B. 1/(0.167 - 0.144) (Correct Answer)
C. 1/(0.300 - 0.267)
D. 1/(0.267 - 0.300)
E. 1/(0.136 - 0.118)

Explanation: ***1/(0.167 - 0.144)*** - The **Number Needed to Treat (NNT)** is calculated as **1 / Absolute Risk Reduction (ARR)**. - The **Absolute Risk Reduction (ARR)** is the difference between the event rate in the control group (16.7%) and the event rate in the treatment group (14.4%), which is **0.167 - 0.144**. *1/(0.144 - 0.167)* - This calculation represents 1 divided by the **Absolute Risk Increase**, which would be relevant if the treatment increased mortality. - The **NNT should always be a positive value**, indicating the number of patients to treat to prevent one adverse event. *1/(0.300 - 0.267)* - This option uses arbitrary numbers (0.300 and 0.267) that do not correspond to the given **mortality rates** in the problem. - It does not reflect the correct calculation for **absolute risk reduction** based on the provided data. *1/(0.267 - 0.300)* - This option also uses arbitrary numbers not derived from the problem's data, and it would result in a **negative value** for the denominator. - The difference between event rates of 0.267 and 0.300 is not present in the given information for this study. *1/(0.136 - 0.118)* - This calculation uses arbitrary numbers (0.136 and 0.118) that are not consistent with the reported **mortality rates** of 14.4% and 16.7%. - These values do not represent the **Absolute Risk Reduction** required for calculating NNT in this specific scenario.

Question 7: A research team is working on a new assay meant to increase the sensitivity of testing in cervical cancer. Current sensitivity is listed at 77%. If this research team's latest work culminates in the following results (listed in the table), has the sensitivity improved, and, if so, then by what percentage? Research team's latest results: | | Patients with cervical cancer | Patients without cervical cancer | |--------------------------|-------------------------------|----------------------------------| | Test is Positive (+) | 47 | 4 | | Test is Negative (-) | 9 | 44 |

A. No, the research team has seen a decrease in sensitivity according to the new results listed.
B. No, the research team has not seen any improvement in sensitivity according to the new results listed.
C. Yes, the research team has seen an improvement in sensitivity of almost 7% according to the new results listed. (Correct Answer)
D. Yes, the research team has seen an improvement in sensitivity of more than 10% according to the new results listed.
E. Yes, the research team has seen an improvement in sensitivity of less than 2% according to new results listed; this improvement is negligible and should be improved upon for significant contribution to the field.

Explanation: ***Yes, the research team has seen an improvement in sensitivity of almost 7% according to the new results listed.*** - **Sensitivity** is calculated as **True Positives / (True Positives + False Negatives)**. From the table: True Positives = 47, False Negatives = 9. - New sensitivity = 47 / (47 + 9) = 47 / 56 $\approx$ **83.9%**. Compared to the current sensitivity of 77%, this is an improvement of 83.9% - 77% = **6.9%**, which is almost 7%. *No, the research team has not seen any improvement in sensitivity according to the new results listed.* - The new sensitivity calculated is **83.9%**, which is indeed higher than the current sensitivity of **77%**. - This option incorrectly states there is no improvement, as a clear increase of nearly 7% is observed. *No, the research team has seen a decrease in sensitivity according to the new results listed.* - The calculated new sensitivity of **83.9%** is higher than the original 77%, indicating an **increase**, not a decrease. - This statement is factually incorrect based on the provided data. *Yes, the research team has seen an improvement in sensitivity of more than 10% according to the new results listed.* - The improvement is approximately **6.9%** (83.9% - 77%), which is less than 10%. - This option overstates the degree of improvement observed. *Yes, the research team has seen an improvement in sensitivity of less than 2% according to new results listed; this improvement is negligible and should be improved upon for significant contribution to the field.* - The calculated improvement is approximately **6.9%**, not less than 2%. - While clinical significance can be debated, the mathematical calculation of improvement is not accurately reflected by "less than 2%".

Question 8: A randomized controlled trial was initiated to evaluate a novel DPP-4 inhibitor for blood glucose management in diabetic patients. The study used a commonly prescribed sulfonylurea as the standard of care treatment. 2,000 patients were enrolled in the study with 1,000 patients in each arm. One of the primary outcomes was the development of diabetic nephropathy during treatment. This outcome occurred in 68 patients on the DPP-4 inhibitor and 134 patients on the sulfonylurea. What is the relative risk reduction (RRR) for patients using the DPP-4 inhibitor compared with the sulfonylurea?

A. 23%
B. 49% (Correct Answer)
C. 33%
D. 59%
E. 43%

Explanation: ***49%*** - To calculate **relative risk reduction (RRR)**, first determine the **event rate (ER)** for each group. - ER (DPP-4 inhibitor) = 68/1000 = 0.068. ER (Sulfonylurea) = 134/1000 = 0.134. - Next, calculate the **absolute risk reduction (ARR)**: ARR = ER (Sulfonylurea) - ER (DPP-4 inhibitor) = 0.134 - 0.068 = 0.066. - Finally, calculate RRR: RRR = ARR / ER (Sulfonylurea) = 0.066 / 0.134 ≈ 0.4925 or **49%**. *23%* - This value is incorrect and does not result from the proper application of the **relative risk reduction (RRR)** formula. - A common mistake is to reverse the subtrahend and minuend in the numerator or denominator. *33%* - This value is incorrect and does not result from the proper application of the **relative risk reduction (RRR)** formula. - Incorrect calculations in either the numerator or denominator of the **RRR formula** would lead to this incorrect result. *59%* - This value is incorrect and is likely the result of an error in calculating either the **absolute risk reduction (ARR)** or dividing it by the wrong **event rate**. - Always ensure the correct event rates are used for the control group and the intervention group. *43%* - This value is incorrect and does not align with the correct calculation of **relative risk reduction (RRR)**. - Errors in setting up the formula or executing the division could lead to this result.

Question 9: A medical research study is evaluating an investigational novel drug (medication 1) as compared with standard therapy (medication 2) in patients presenting to the emergency department with myocardial infarction (MI). The study enrolled a total of 3,000 subjects, 1,500 in each study arm. Follow-up was conducted at 45 days post-MI. The following are the results of the trial: Endpoints Medication 1 Medication 2 P-Value Primary: death from cardiac causes 134 210 0.03 Secondary: hyperkalemia 57 70 0.4 What is the relative risk of death from a cardiac cause, expressed as a percentage? (Round to the nearest whole number.)

A. 64% (Correct Answer)
B. 42%
C. 72%
D. 36%
E. 57%

Explanation: ***64%*** - The **relative risk (RR)** is calculated as the event rate in the exposed group divided by the event rate in the unexposed (control) group. - For cardiac death, the event rate for Medication 1 is 134/1500 = 0.0893, and for Medication 2 is 210/1500 = 0.14. Therefore, RR = 0.0893 / 0.14 = 0.6378. - Expressing as a percentage: 0.6378 × 100 = 63.78%, which rounds to **64%**. - This indicates that Medication 1 has 64% of the risk of cardiac death compared to Medication 2, representing a **36% relative risk reduction**. *42%* - This option is incorrect as it does not reflect the accurate calculation of **relative risk** using the provided event rates. - A calculation error or conceptual misunderstanding of the relative risk formula would lead to this value. *72%* - This percentage is higher than the calculated relative risk, suggesting an incorrect application of the formula or a misinterpretation of the event rates. - It does not represent the ratio of risk between the two medication groups for cardiac death. *36%* - This value represents the **relative risk reduction** (100% - 64% = 36%), not the relative risk itself. - This is a common error where students confuse relative risk with relative risk reduction. *57%* - While closer to the correct answer, this value is not the precise result when rounding to the nearest whole number. - Small calculation discrepancies or rounding at intermediate steps could lead to this slightly different percentage.

Question 10: A first time mother of a healthy, full term, newborn girl is anxious about sudden infant death syndrome. Which of the following pieces of advice can reduce the risk of SIDS?

A. Sleep supine in a crib with bumpers, head propped up on a pillow, and wrapped in a warm blanket
B. Sleep supine in a crib with bumpers, head propped up on a pillow, and wrapped in an infant sleeper
C. Sleep supine in the parent's bed and use a pacifier after 1 month of age
D. Sleep supine in a crib without bumpers, use a pacifier after 1 month of age, and use a home apnea monitor
E. Sleep supine in a crib without bumpers, use a pacifier after 1 month of age, and avoid smoking (Correct Answer)

Explanation: ***Sleep supine in a crib without bumpers, use a pacifier after 1 month of age, and avoiding smoking*** - **Sleeping supine** (on the back) is the most critical recommendation to reduce SIDS risk, and a **crib without bumpers** and other soft bedding reduces smothering hazards. - **Pacifier use** after the first month of age has been shown to be protective, and **avoiding smoking** around the infant is crucial as exposure to tobacco smoke significantly increases SIDS risk. *Sleep supine in a crib with bumpers, head propped up on a pillow, and wrapped in a warm blanket* - While **sleeping supine** is correct, **bumpers, pillows, and loose blankets** in the crib are significant risk factors for SIDS, as they can cause accidental suffocation. - The use of **pillows** is not recommended for infants due to the risk of airway obstruction and suffocation. *Sleep supine in a crib with bumpers, head propped up on a pillow, and wrapped in an infant sleeper* - Similar to the previous option, **bumpers and a pillow** are unsafe as they pose a suffocation risk and should be avoided in an infant's sleep environment. - While an **infant sleeper** (or sleep sack) is generally safer than a loose blanket, the presence of bumpers and a pillow negates this benefit. *Sleep supine in the parent's bed and use a pacifier after 1 month of age* - **Co-sleeping (sharing a bed with parents)** significantly increases the risk of SIDS and accidental suffocation, especially if parents smoke, are impaired, or if heavy bedding is present. - Although **pacifier use** is recommended, sleeping in the parent's bed is a major risk factor that outweighs any potential benefit here. *Sleep supine in a crib without bumpers, use a pacifier after 1 month of age, and use a home apnea monitor* - While **sleeping supine** in a **crib without bumpers** and **pacifier use** are correct recommendations, **home apnea monitors** are not recommended for routine SIDS prevention in healthy infants. - Apnea monitors have not been shown to reduce the incidence of SIDS and can lead to false alarms and unnecessary anxiety without proven benefit.

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