Competing risks — MCQs

10 questions

Two separate investigators have conducted cohort studies to calculate the risk of lymphoma in rheumatoid arthritis patients taking anti-TNF alpha medications. They each followed patients with rheumatoid arthritis for a number of years and tracked the number of patients who were diagnosed with lymphoma. The results of the two studies are summarized in the table. Number of patients Follow-up period Number of new cases of lymphoma Study 1 3000 10 years 30 Study 2 300 30 years 9 Based on these results, which of the following statements about the risk of lymphoma is most accurate?

A 25-year-old man with a genetic disorder presents for genetic counseling because he is concerned about the risk that any children he has will have the same disease as himself. Specifically, since childhood he has had difficulty breathing requiring bronchodilators, inhaled corticosteroids, and chest physiotherapy. He has also had diarrhea and malabsorption requiring enzyme replacement therapy. If his wife comes from a population where 1 in 10,000 people are affected by this same disorder, which of the following best represents the likelihood a child would be affected as well?

A researcher is designing an experiment to examine the toxicity of a new chemotherapeutic agent in mice. She splits the mice into 2 groups, one of which she exposes to daily injections of the drug for 1 week. The other group is not exposed to any intervention. Both groups are otherwise raised in the same conditions with the same diet. One month later, she sacrifices the mice to check for dilated cardiomyopathy. In total, 52 mice were exposed to the drug, and 50 were not exposed. Out of the exposed group, 13 were found to have dilated cardiomyopathy on necropsy. In the unexposed group, 1 mouse was found to have dilated cardiomyopathy. Which of the following is the relative risk of developing cardiomyopathy with this drug?

A biostatistician is processing data for a large clinical trial she is working on. The study is analyzing the use of a novel pharmaceutical compound for the treatment of anorexia after chemotherapy with the outcome of interest being the change in weight while taking the drug. While most participants remained about the same weight or continued to lose weight while on chemotherapy, there were smaller groups of individuals who responded very positively to the orexic agent. As a result, the data had a strong positive skew. The biostatistician wishes to report the measures of central tendency for this project. Just by understanding the skew in the data, which of the following can be expected for this data set?

An epidemiologist is evaluating the efficacy of Noxbinle in preventing HCC deaths at the population level. A clinical trial shows that over 5 years, the mortality rate from HCC was 25% in the control group and 15% in patients treated with Noxbinle 100 mg daily. Based on this data, how many patients need to be treated with Noxbinle 100 mg to prevent, on average, one death from HCC?

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 population is studied for risk factors associated with testicular cancer. Alcohol exposure, smoking, dietary factors, social support, and environmental exposure are all assessed. The researchers are interested in the incidence and prevalence of the disease in addition to other outcomes. Which pair of studies would best assess the 1. incidence and 2. prevalence?

Many large clinics have noticed that the prevalence of primary biliary cholangitis (PBC) has increased significantly over the past 20 years. An epidemiologist is working to identify possible reasons for this. After analyzing a series of nationwide health surveillance databases, the epidemiologist finds that the incidence of PBC has remained stable over the past 20 years. Which of the following is the most plausible explanation for the increased prevalence of PBC?

A researcher wants to determine whether there is an association between CRP values and the risk of MI or cancer. Four relative risk (RR) values were plotted $(0.5,1.5,1.7,1.8)$ with respect to CRP levels. What conclusion can be drawn?

Q10

A researcher wants to study the carcinogenic effects of a food additive. From the literature, he finds that 7 different types of cancers have been linked to the consumption of this food additive. He wants to study all 7 possible outcomes. He conducts interviews with people who consume food containing these additives and people who do not. He then follows both groups for several years to see if they develop any of these 7 cancers or any other health outcomes. Which of the following study models best represents this study?

Competing risks US Medical PG Practice Questions and MCQs

Question 1: Two separate investigators have conducted cohort studies to calculate the risk of lymphoma in rheumatoid arthritis patients taking anti-TNF alpha medications. They each followed patients with rheumatoid arthritis for a number of years and tracked the number of patients who were diagnosed with lymphoma. The results of the two studies are summarized in the table. Number of patients Follow-up period Number of new cases of lymphoma Study 1 3000 10 years 30 Study 2 300 30 years 9 Based on these results, which of the following statements about the risk of lymphoma is most accurate?

A. The risk is higher in study 1, with an incidence rate of 30 cases per 10 person-years
B. The risks are equivalent, with a prevalence of 39 cases per 3300 persons
C. The risks are equivalent, with an incidence rate of 1 case per 1000 person-years (Correct Answer)
D. The risk is higher in study 1, with a prevalence of 30 cases per 3000 patients
E. The risk is higher in study 2, with a cumulative incidence of 9 cases per 300 patients

Explanation: **The risks are equivalent, with an incidence rate of 1 case per 1000 person-years** - To calculate the **incidence rate**, divide the number of new cases by the total person-time at risk. - For Study 1: 30 cases / (3000 persons × 10 years) = 30 / 30,000 = 0.001 cases per person-year, or **1 case per 1000 person-years**. - For Study 2: 9 cases / (300 persons × 30 years) = 9 / 9,000 = 0.001 cases per person-year, or **1 case per 1000 person-years**. - Both studies yield the same incidence rate, indicating equivalent risk. *The risk is higher in study 1, with an incidence rate of 30 cases per 10 person-years* - The calculation "30 cases per 10 person-years" incorrectly uses the follow-up period instead of the total person-time at risk across all participants. - This calculation does not accurately reflect the **incidence rate** as it doesn't account for the number of individuals in the study. *The risks are equivalent, with a prevalence of 39 cases per 3300 persons* - **Prevalence** refers to existing cases at a specific point in time, not new cases over a period. - This calculation incorrectly combines data from two separate studies as if it were a single point prevalence, which is methodologically incorrect. *The risk is higher in study 1, with a prevalence of 30 cases per 3000 patients* - This statement uses a calculation that resembles **cumulative incidence** (new cases divided by initial population) for Study 1, but incorrectly labels it as prevalence. - A cumulative incidence of 30/3000 = 0.01 (or 1%) for Study 1 does not account for the duration of follow-up, making direct comparison with Study 2 (which has a 30-year follow-up) inappropriate. *The risk is higher in study 2, with a cumulative incidence of 9 cases per 300 patients* - Study 2 has a **cumulative incidence** of 9/300 = 0.03 (or 3%) over 30 years. - Comparing cumulative incidence directly between studies with different follow-up durations (10 years vs. 30 years) is not appropriate for assessing the underlying risk rate, as it does not account for the time component.

Question 2: A 25-year-old man with a genetic disorder presents for genetic counseling because he is concerned about the risk that any children he has will have the same disease as himself. Specifically, since childhood he has had difficulty breathing requiring bronchodilators, inhaled corticosteroids, and chest physiotherapy. He has also had diarrhea and malabsorption requiring enzyme replacement therapy. If his wife comes from a population where 1 in 10,000 people are affected by this same disorder, which of the following best represents the likelihood a child would be affected as well?

A. 0.01%
B. 2%
C. 0.5%
D. 1% (Correct Answer)
E. 50%

Explanation: ***Correct Option: 1%*** - The patient's symptoms (difficulty breathing requiring bronchodilators, inhaled corticosteroids, and chest physiotherapy; diarrhea and malabsorption requiring enzyme replacement therapy) are classic for **cystic fibrosis (CF)**, an **autosomal recessive disorder**. - For an autosomal recessive disorder with a prevalence of 1 in 10,000 in the general population, **q² = 1/10,000**, so **q = 1/100 = 0.01**. The carrier frequency **(2pq)** is approximately **2q = 2 × (1/100) = 1/50 = 0.02**. - The affected man is **homozygous recessive (aa)** and will always pass on the recessive allele. His wife has a **1/50 chance of being a carrier (Aa)**. If she is a carrier, she has a **1/2 chance of passing on the recessive allele**. - Therefore, the probability of an affected child = **(Probability wife is a carrier) × (Probability wife passes recessive allele) = 1/50 × 1/2 = 1/100 = 1%**. *Incorrect Option: 0.01%* - This percentage is too low and does not correctly account for the carrier frequency in the population and the probability of transmission from a carrier mother. *Incorrect Option: 2%* - This represents approximately the carrier frequency (1/50 ≈ 2%), but does not account for the additional 1/2 probability that a carrier mother would pass on the recessive allele. *Incorrect Option: 0.5%* - This value would be correct if the carrier frequency were 1/100 instead of 1/50, which does not match the given population prevalence. *Incorrect Option: 50%* - **50%** would be the risk if both parents were carriers of an autosomal recessive disorder (1/4 chance = 25% for affected, but if we know one parent passes the allele, conditional probability changes). More accurately, 50% would apply if the disorder were **autosomal dominant** with one affected parent, which is not the case here.

Question 3: A researcher is designing an experiment to examine the toxicity of a new chemotherapeutic agent in mice. She splits the mice into 2 groups, one of which she exposes to daily injections of the drug for 1 week. The other group is not exposed to any intervention. Both groups are otherwise raised in the same conditions with the same diet. One month later, she sacrifices the mice to check for dilated cardiomyopathy. In total, 52 mice were exposed to the drug, and 50 were not exposed. Out of the exposed group, 13 were found to have dilated cardiomyopathy on necropsy. In the unexposed group, 1 mouse was found to have dilated cardiomyopathy. Which of the following is the relative risk of developing cardiomyopathy with this drug?

A. 12.5 (Correct Answer)
B. 25.0
C. 13.7
D. 16.3
E. 23.0

Explanation: ***Correct Option: 12.5*** - The **relative risk (RR)** is calculated as the **risk in the exposed group divided by the risk in the unexposed group**: RR = [a/(a+b)] / [c/(c+d)] - **Risk in exposed group** = 13/52 = 0.25 (25%) - **Risk in unexposed group** = 1/50 = 0.02 (2%) - **RR = 0.25 / 0.02 = 12.5** - This indicates that mice exposed to the chemotherapeutic agent are **12.5 times more likely** to develop dilated cardiomyopathy compared to unexposed mice - An **RR > 1** indicates increased risk with exposure, supporting the drug's cardiotoxicity *Incorrect Option: 25.0* - This value results from **miscalculating the unexposed group risk** (e.g., using 0.01 instead of 0.02 as the denominator) - If the unexposed risk was halved incorrectly: 0.25 / 0.01 = 25.0 - This overestimates the relative risk by a factor of 2 *Incorrect Option: 13.7* - This value does not result from the correct **relative risk formula** - May arise from an **arithmetic error** or confusion with other epidemiological measures - The correct calculation of 13/52 ÷ 1/50 does not yield this result *Incorrect Option: 16.3* - This might result from **miscounting the number of subjects** in either group or confusing **relative risk with odds ratio** - The **odds ratio** would be calculated as (13/39) / (1/49) = 16.3 - Remember: **Relative risk uses total exposed/unexposed as denominators**, while odds ratio uses non-diseased counts *Incorrect Option: 23.0* - This value suggests a **fundamental error** in applying the relative risk formula - Could result from using incorrect numerators or denominators (e.g., 13/1 instead of proper risk calculation) - Significantly overestimates the true relative risk of 12.5

Question 4: A biostatistician is processing data for a large clinical trial she is working on. The study is analyzing the use of a novel pharmaceutical compound for the treatment of anorexia after chemotherapy with the outcome of interest being the change in weight while taking the drug. While most participants remained about the same weight or continued to lose weight while on chemotherapy, there were smaller groups of individuals who responded very positively to the orexic agent. As a result, the data had a strong positive skew. The biostatistician wishes to report the measures of central tendency for this project. Just by understanding the skew in the data, which of the following can be expected for this data set?

A. Mean = median = mode
B. Mean < median < mode
C. Mean > median > mode (Correct Answer)
D. Mean > median = mode
E. Mean < median = mode

Explanation: ***Mean > median > mode*** - In a dataset with a **strong positive skew**, the tail of the distribution is on the right, pulled by a few **unusually large values**. - These extreme high values disproportionately influence the **mean**, pulling it to the right (higher value), while the **median** (middle value) is less affected, and the **mode** (most frequent value) is often located at the peak of the distribution towards the left. *Mean = median = mode* - This relationship between the measures of central tendency is characteristic of a **perfectly symmetrical distribution**, such as a **normal distribution**, where there is no skew. - In a symmetrical distribution, the mean, median, and mode are all located at the exact center of the data. *Mean < median < mode* - This order is typical for a dataset with a **negative skew**, where the tail is on the left due to a few **unusually small values**. - In a negatively skewed distribution, the mean is pulled to the left (lower value) by the small values, making it less than the median and mode. *Mean > median = mode* - This configuration is generally not characteristic of standard skewed distributions and would imply a specific, less common bimodal or complex distribution shape where the mode coincides with the median, but the mean is pulled higher. - While theoretically possible, it doesn't describe a typical positively skewed distribution where the mode is usually the lowest of the three. *Mean < median = mode* - This relationship would suggest a negatively skewed distribution where the median and mode are equal, but the mean is pulled to the left (lower value) by a leftward tail. - Again, this is a less typical representation of a standard negatively skewed distribution, which often follows the Mean < Median < Mode pattern.

Question 5: An epidemiologist is evaluating the efficacy of Noxbinle in preventing HCC deaths at the population level. A clinical trial shows that over 5 years, the mortality rate from HCC was 25% in the control group and 15% in patients treated with Noxbinle 100 mg daily. Based on this data, how many patients need to be treated with Noxbinle 100 mg to prevent, on average, one death from HCC?

A. 20
B. 73
C. 10 (Correct Answer)
D. 50
E. 100

Explanation: ***10*** - The **number needed to treat (NNT)** is calculated by first finding the **absolute risk reduction (ARR)**. - **ARR** = Risk in control group - Risk in treatment group = 25% - 15% = **10%** (or 0.10). - **NNT = 1 / ARR** = 1 / 0.10 = **10 patients**. - This means that **10 patients must be treated with Noxbinle to prevent one death from HCC** over 5 years. *20* - This would result from an ARR of 5% (1/0.05 = 20), which is not supported by the data. - May arise from miscalculating the risk difference or incorrectly halving the actual ARR. *73* - This value does not correspond to any standard calculation of NNT from the given mortality rates. - May result from confusion with other epidemiological measures or calculation error. *50* - This would correspond to an ARR of 2% (1/0.02 = 50), which significantly underestimates the actual risk reduction. - Could result from incorrectly calculating the difference as a proportion rather than absolute percentage points. *100* - This would correspond to an ARR of 1% (1/0.01 = 100), grossly underestimating the treatment benefit. - May result from confusing ARR with relative risk reduction or other calculation errors.

Question 6: 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

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.

Question 7: A population is studied for risk factors associated with testicular cancer. Alcohol exposure, smoking, dietary factors, social support, and environmental exposure are all assessed. The researchers are interested in the incidence and prevalence of the disease in addition to other outcomes. Which pair of studies would best assess the 1. incidence and 2. prevalence?

A. 1. Prospective cohort study 2. Cross sectional study (Correct Answer)
B. 1. Prospective cohort study 2. Retrospective cohort study
C. 1. Cross sectional study 2. Retrospective cohort study
D. 1. Case-control study 2. Prospective cohort study
E. 1. Clinical trial 2. Cross sectional study

Explanation: ***1. Prospective cohort study 2. Cross sectional study*** - A **prospective cohort study** is ideal for measuring **incidence** (new cases over time) because it follows a group of individuals forward in time to observe who develops the disease. - A **cross-sectional study** is suitable for measuring **prevalence** (existing cases at a specific point in time) as it surveys a population at one moment to determine the proportion with the disease. *1. Prospective cohort study 2. Retrospective cohort study* - A **retrospective cohort study** assesses past exposures and outcomes and can measure incidence, but it is not the primary choice for prevalence. - While a prospective cohort study is appropriate for incidence, a retrospective cohort study is less suited for determining current prevalence. *1. Cross sectional study 2. Retrospective cohort study* - A **cross-sectional study** measures prevalence, not incidence, as it captures disease status at a single point in time. - A **retrospective cohort study** looks back in time to identify past exposures and subsequent outcomes, which is not the best method for current prevalence. *1. Case-control study 2. Prospective cohort study* - A **case-control study** compares exposures between individuals with a disease (cases) and those without (controls) and is best for studying rare diseases and estimating odds ratios, not incidence or prevalence directly. - A **prospective cohort study** is suitable for incidence, but a case-control study is not for incidence or prevalence. *1. Clinical trial 2. Cross sectional study* - A **clinical trial** is an experimental study designed to test the efficacy of interventions and is not primarily used to measure disease incidence or prevalence in a general population. - While a cross-sectional study is appropriate for prevalence, a clinical trial is not designed for incidence measurement.

Question 8: Many large clinics have noticed that the prevalence of primary biliary cholangitis (PBC) has increased significantly over the past 20 years. An epidemiologist is working to identify possible reasons for this. After analyzing a series of nationwide health surveillance databases, the epidemiologist finds that the incidence of PBC has remained stable over the past 20 years. Which of the following is the most plausible explanation for the increased prevalence of PBC?

A. Improved quality of care for PBC (Correct Answer)
B. Increased availability of diagnostic testing for PBC
C. Increased exposure to environmental risk factors for PBC
D. Increased awareness of PBC among clinicians
E. Increased average age of the population at risk for PBC

Explanation: ***Improved quality of care for PBC*** - This leads to a **longer survival time** for patients with PBC. When incidence remains stable but patients live longer, the cumulative number of living cases (prevalence) naturally increases. - An increase in prevalence with stable incidence is a classic indicator of **improved patient survival** due to better management or treatment. *Increased availability of diagnostic testing for PBC* - This would primarily impact the **incidence** of PBC by detecting more cases that were previously undiagnosed. The question states that the incidence has remained stable. - While improved diagnostics might initially increase *reported* incidence, if the true incidence is stable, it wouldn't explain a sustained rise in prevalence without a corresponding change in incidence or survival. *Increased exposure to environmental risk factors for PBC* - This would directly lead to an **increase in the incidence** of PBC, as more people would be developing the disease. - Since the incidence is stable, an increase in environmental risk factors is not the most plausible explanation for increased prevalence. *Increased awareness of PBC among clinicians* - Similar to increased diagnostic testing, increased awareness would likely lead to the diagnosis of more new cases, thus **increasing the incidence** of PBC. - A stable incidence despite increased awareness means that the actual rate of new cases developing the disease has not changed, ruling this out as the primary cause of increased prevalence. *Increased average age of the population at risk for PBC* - An aging population could potentially increase the incidence of age-related diseases. However, if the **incidence has remained stable**, it implies that even with an older population, the rate of new diagnoses has not increased. - While age is a risk factor for PBC, an increase in prevalence without a change in incidence suggests a factor influencing the duration of the disease rather than its onset.

Question 9: A researcher wants to determine whether there is an association between CRP values and the risk of MI or cancer. Four relative risk (RR) values were plotted $(0.5,1.5,1.7,1.8)$ with respect to CRP levels. What conclusion can be drawn?

A. CRP has no relationship
B. CRP decreases & disease decreases
C. CRP increases disease/cancer risk (Correct Answer)
D. No association in first interval
E. CRP shows protective effect in first interval

Explanation: ***CRP increases disease/cancer risk*** - A **relative risk (RR)** greater than 1 indicates an increased risk of the outcome (MI or cancer) in the exposed group (higher CRP levels) compared to the unexposed group. - The plots show RRs of 1.5, 1.7, and 1.8, all of which are greater than 1, consistently indicating that higher CRP levels are associated with an elevated risk for MI or cancer. - The overall trend across the four intervals demonstrates a positive association between CRP and disease risk. *CRP has no relationship* - This conclusion is incorrect because three of the four plotted RR values (1.5, 1.7, 1.8) are above 1, indicating a positive association or increased risk. - An RR of 1 signifies no relationship, but the majority of values clearly deviate from 1, showing a definite association. *CRP decreases & disease decreases* - While one RR value (0.5) suggests a decreased risk, the majority of the given RRs (1.5, 1.7, 1.8) are greater than 1, indicating an increased risk. - This option would only be true if all or most RR values were less than 1, implying a protective effect, which is not the overall trend here. *No association in first interval* - The first interval shows an RR of 0.5. An RR of 1 indicates no association, while an RR of 0.5 actually indicates a **decreased risk or protective effect**, rather than no association. - Therefore, stating "no association" for the first interval is inaccurate given the definition of relative risk. *CRP shows protective effect in first interval* - While the first interval RR of 0.5 does suggest a protective effect in isolation, this option fails to capture the **overall conclusion** from all four data points. - When interpreting multiple RR values together, the predominant pattern (three values >1) indicates an overall increased risk, making this a misleading conclusion for the study as a whole.

Question 10: A researcher wants to study the carcinogenic effects of a food additive. From the literature, he finds that 7 different types of cancers have been linked to the consumption of this food additive. He wants to study all 7 possible outcomes. He conducts interviews with people who consume food containing these additives and people who do not. He then follows both groups for several years to see if they develop any of these 7 cancers or any other health outcomes. Which of the following study models best represents this study?

A. Cohort study (Correct Answer)
B. Case-control study
C. Cross-sectional study
D. Randomized clinical trial
E. Crossover study

Explanation: ***Cohort study*** - This study design involves selecting a group based on their **exposure status** (consumers vs. non-consumers of the food additive) and **following them forward in time** to observe the incidence of outcomes (cancers). - It is ideal for studying **multiple potential outcomes** from a single exposure and for establishing the **temporal relationship** between exposure and disease. *Case-control study* - This design starts by identifying individuals with a particular **outcome (cases)** and comparing them to individuals without the outcome (controls) to look back for **past exposures**. - It is efficient for studying **rare diseases** or when multiple exposures are suspected for a single outcome, which is inverse to the scenario described. *Cross-sectional study* - This study measures both **exposure and outcome simultaneously** at a single point in time, providing a snapshot of prevalence. - It cannot establish a **temporal relationship** between exposure and outcome and is less suitable for studying incident diseases that develop over time. *Randomized clinical trial* - This design involves **randomly assigning participants** to an intervention group or a control group and following them for outcomes. - It is primarily used to evaluate the **efficacy of interventions** or treatments, not to study the carcinogenic effects of naturally occurring exposures. *Crossover study* - In a crossover design, participants **receive all interventions** in a specific sequence, making each subject serve as their own control. - This design is generally used for evaluating **short-term effects of treatments** in chronic, stable conditions and is unsuitable for observing the development of diseases like cancer over extended periods.

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free