Epidemiology 📈

A group of patients with atherosclerosis are followed forward over a period of time to investigate the outcome according to exposure to different factors. It started with 2 groups free of disease and followed forward for a period of time. What is the SINGLE most likely study design?

A new drug called “Prostagist” is undergoing clinical trials for the prevention of prostate cancer. The trial looks at the incidence of prostate cancer within a 5 year period. The following is the data obtained from the study:

What is the relative risk reduction?

A study is trialling a new drug called Cardioprev for secondary prevention of cardiovascular events. The study seeks to determine whether or not Cardioprev reduces the risk of mortality compared to a placebo. In the randomised control trial 100 patients were assigned treatment with Cardioprev and 100 control group patients were assigned a placebo drug. The mean study duration was 60 months and the mean average age was 63 years old. All-cause mortality was 349% for Cardioprev and 40% for the control group (95% CI: 0.74-0.93], p=0.0017). Which of the following represents the number of patients needed to treat to save 1 life with Cardioprev?

5000 patients were screened for skin cancer using new image recognition technology powered by artificial intelligence. The new technology reported 500 patients had suspicious lesions, which on biopsy only 100 proved to be cancerous. An additional 5 patients who were not picked up by the new computer program to have cancer, later developed skin cancer. Which term describes the 400 patients who were negative on biopsy?

A new test called “LIMA” has been developed to identify pancreatic cancer. In the study, 50 patients with a positive LIMA had confirmed pancreatic cancer on biopsy. 20 patients with a negative LIMA had a confirmed pancreatic cancer on biopsy. 500 patients with a negative LIMA had a biopsy that excluded pancreatic cancer. 5 patients with a positive LIMA had a biopsy that excluded pancreatic cancer. What is the positive predictive value of the LIMA test?

A new test called “DIVE” has been developed to identify deep venous thrombosis. In the study, 60 patients with a positive DIVE had a confirmed DVT on an ultrasound scan. 40 patients with a negative DIVE had a confirmed DVT on ultrasound scan. 300 patients with a negative DIVE had an ultrasound scan excluded DVT. 100 patients with a positive DIVE had an ultrasound scan excluding DVT. What is the specificity of the DIVE test?

A screening test in the form of a questionnaire is being used to pick up patients with dementia attending their GP appointments. Patients above 80 years of age were given a questionnaire. The total score is 100. Patients who scored less than 82 were thought to have symptoms of dementia and were offered further appointments to diagnose this. This screening test has a sensitivity of 0.84. What is the interpretation of the sensitivity given?

A study involving a new screening test to identify a protein called ‘ABLE-55’ is being used to determine patients at risk of breast cancer. Following testing, breast biopsies are used as the gold standard to confirm the presence or absence of breast cancer. The initial studies have revealed the following results:

Which is the best term to describe the cell with the 44 patients?

Two groups of women with osteoporosis were recruited to be involved in a study. They were divided using allocation software into separate groups. One group of women were given drug A. The other group of women were given a placebo. Both groups of women were then followed up at frequent intervals for their progression of osteoporosis for the next 10 years. What is the SINGLE most likely type of clinical study in this scenario?

A study was performed to compare oesophageal cancer in individuals who are smokers with their matched controls. The study looked at the last 3 years of data. Individuals who smoked were associated with higher odds of oesophageal cancer. What is this type of study?

This is the measure of dispersion of a set of values. What is the SINGLE most likely term?

A study was done to evaluate breast cancer using a mammogram. 10,000 patients were screened for breast cancer using a mammogram. 1,000 patients had an abnormal mammogram and had a further biopsy. Of those who went for biopsy, 100 of them had histology which showed breast cancer. 10 patients out of the 9,000 patients who had a normal mammogram were found to have cancer on biopsy. Which term best describes the group of 10 patients who tested positive on biopsy?

Half of a group of observations lies above this level and it is particularly important if the distributions are not normal. What is the SINGLE most likely term?

A clinical trial was performed looking at a new drug. It is thought that this new drug is able to modify cardiovascular risk factors and reduce the risk of a myocardial infarction. 200 patients were randomised into two separate groups. One group received the new drug while the other group received the placebo. The participants were followed up for 10 years. The results are below.

What is the number needed to treat for this new drug to prevent one myocardial infarction?

10,000 women were involved in a study looking at a “new cervical test” to detect cervical cancer. 1,000 of the women who had this “new cervical test” had positive results. 100 of these women who tested positive had colposcopy and biopsy that showed negative results for cervical cancer. 10 of the 9,000 women who tested negative for the “new cervical test” had a colposcopy and biopsy that showed positive results for cervical cancer. What is the most appropriate term to describe the 9,000 women?

10000 women underwent a newly developed cervical smear screen. 1000 of them had a smear result which shows premalignant changes and had further investigations and biopsies. Only 100 women who had undergone biopsies had premalignancy changes seen on histology. What is the SINGLE best term to describe the the cervical smear test?

A study was carried out in which 10 000 women participated. All the women underwent a cervical smear. 1000 of 10 000 women had a positive smear. Of these, 100 developed cervical cancer. 10 women who had negative smear developed cancer. What is the SINGLE most likely terminology used to describe the 10 women with negative results who developed cervical cancer?

A 22 year old woman presents to the GP with symptoms of acute sinusitis. The current statistical benefit of antibiotic use in acute sinusitis is seen below:

Numbers needed to treat for a course of antibiotic fall between 7 and 21

Numbers needed to harm for a course of antibiotics falls between 8 and 11

What does “numbers needed to harm” mean?

A total of 50 people were on board an aircraft travelling to London from Rome. A week later, 5 passengers who were British nationals developed flu-like symptoms and were all tested positive for the new ABLE-77 virus. ABLE-77 is a new virus which has not previously been seen in the UK. One incubation period later, 10 household members of the ABLE-77 positive passengers also tested positive for the same virus. If the total number of all the household members of the 5 passengers is 25 (inclusive of the 5 passengers), what is the secondary attack rate amongst household contacts?

1,000 patients were evaluated for premalignant and malignant oral lesions by fluorescent light. A total of 200 of them had abnormal lesions which required biopsy which was considered the gold standard for detection of lesion’s histology. 20 of the remaining 800 patients who initially did not show any abnormal lesions using fluorescent light, developed oral cancer which was confirmed by biopsy within 2 months. Of all the biopsies of patients who had an abnormal lesion seen on fluorescent light, 50 patients’ results showed premalignant or malignant changes. Which term accurately describes the 20 patients who developed oral cancer without any abnormal lesions seen on fluorescent light?

A study is conducted to test the efficacy of non-pharmacological therapy for patients with psychosis. 10 patients with psychosis were assembled by researchers and then interviewed about their experience with non-pharmacological therapy. What type of study is this?

A small town has a population of 250,000. In a five year period there was 1,000 cases of lung cancer diagnosed in that town. The neighbouring town also has a population of 250,000 but only 400 people were diagnosed with lung cancer during the five year period. What is the annual incidence per million of lung cancer in the population of both of these towns?

A study was conducted to look for associations between hard water and childhood eczema. Patients were selected and allocated into 2 groups by the method of computerised generated randomisation. Group A had a water softener installed in their homes before the birth of their child. Group B was the control group and did not have any changes to their water system. Both groups were followed for 6 months with monthly follow-ups and skin testing of the newborns. The researchers did not know which groups the patients were allocated throughout the study. What is the SINGLE most likely study design?

A total of 5,000 women are studied to evaluate premalignant and malignant cervical lesions by smear. All 5,000 women were screened for cervical cancer using a smear test. 1,000 of these women had an abnormal smear. All 1,000 women who had an abnormal smear underwent a colposcopy and biopsy. Of those who went for a biopsy, 20 of them had a histology that showed premalignant changes. Which term accurately describes the 20 women?

A study was performed to determine the relationship between specific seat belts and head injuries during a car accident. Two groups were randomly selected. One group wore standard car seat belts, and the other group wore a new safety seatbelt called “Zeen”. They were followed for over 5 years. Accidents and head injuries were recorded. Of those who had car accidents, the data was inserted into a table which is seen below:

A study was performed looking at a new screening test. It is thought that this new test is able to detect breast cancer in those women who had a breast lump. Those who underwent the screening later had a biopsy as a gold standard test to identify breast cancer. The data of the study is seen below:

 What is the positive predictive value for the new scanning method?

5000 people were recruited in an observational study that looked at the efficacy of COVID vaccines. The candidates were picked base on their vaccine type. One group of people had vaccine A and the other group had vaccine B. The researchers looked at who received which vaccine and studied their outcomes. They were followed in time to determine the likelihood of becoming COVID-positive. What study design is this?

A total of 10,000 patients are studied to evaluate bowel cancer using a faecal immunochemical test (FIT). All 10,000 patients were screened for bowel cancer using FIT. 1,000 patients had a positive result. All 1,000 with the positive result underwent a colonoscopy and biopsy of which 100 of them had histology which showed bowel cancer while the remaining 900 tested negative. In this study, which term accurately describes the 900 patients who tested negative on biopsy?

A new screening test has been devised to detect early stages of prostate cancer. The test has been found to be positive in a high number of patients who are later discovered not to have the cancer on other more definitive testing methods. What is the correct term to describe this test?

2 large groups of people are to be studied over a period of 5 years. The first group which consist of 450 patients have been taking medication A. The second group which consist of 550 patients have been taking medication B. All 1000 participants are to be followed to investigate the outcome of the medications. What is the SINGLE most likely study design?

A study examines the effects of smoking in 200 people aged 50 years and above for a period of 5 years. 100 of them were smokers and the other 100 were non-smokers. In the period of 5 year follow up, 6 people from the smoking group developed chronic obstructive pulmonary disease (COPD) and 2 people from the non-smoking group developed COPD. What is the relative risk of developing COPD in the smoking group?

A new study was conducted to investigate the benefit of extending the age of survival in women having a new cervical smear test. It involved women above 65 years of age who attended their cervical screening regularly, irregularly or not at all in the 5 years prior to their diagnosis of cervical cancer. Using a wide database, the reports statistically showed improvements in overall survival and this new cervical smear test was associated with increased survival. The 5-year survival rate was 91% amongst the women with regular screening, 88% in women with irregular screening and 84% in women without screening. What type of bias could have led to this result?

A double-blind study was designed to test the efficacy of a new statin. One group of patients consisting of 425 people were given a placebo drug and the other group of patients consisting of 501 were given the active drug. Both groups were to be followed up for two years. Within the first 6 months, 25% of participants in the placebo group dropped out of the study and 19% of participants taking the active drug dropped out of the study. What is the SINGLE best explanation for this occurrence?

A new “point of care” screening test is being developed to identify a protein called ‘ROVR’ which is used to determine patients who are infected with a new strain of coronavirus. The test is performed on respiratory samples obtained by a nasopharyngeal swab. Following testing, PCR is used as the gold standard to confirm the presence or absence of the new strain of coronavirus. The initial studies have revealed the following results:

Which is the correct value that represents the accuracy of the new screening test?

A 55 year old man who lives in the UK attends the genetic clinic for advice on his risk of colorectal cancer. He has been told by the genetic team that his odds of developing colorectal cancer is 2.3 based on his strong family history of the disease and genetic studies. The incidence of colorectal cancer in the UK is 4%. Which number below comes closest to the personal risk of this patient developing colorectal cancer?

A study was conducted to evaluate the risk for blindness in a patient with diabetes over a 5-year period. 4 people became blind in Group A which consist of 100 people. 3 people became blind in group B which consisted of 100 people. All participants in group B were given a trial of a new drug whereas group A did not receive any treatment. Given the data above, which statement is correct?

A study was done to determine the efficacy of a new screening method to detect cervical cancer compared to the current conventional method. The results of the study show a p- value of 0.4. Which of the following is true?

A study involving a new screening test to identify a protein called ‘LUN-58’ is being used to determine patients at risk of lung carcinoma. Following testing, lung biopsies are used as the gold standard to confirm the presence or absence of the lung carcinoma. The initial studies have revealed the following results:

Which is the correct value that represents the sensitivity of LUN-58 as a screening test?

Each year 950 000 people develop myocardial infarction in a population of 250 000 000. Out of these, 215 000 die and 112 500 in the first hour. Which of the following is the SINGLE most likely value for the incidence of myocardial infarction?

A total of 10,000 women are studied to evaluate premalignant and malignant cervical lesions by smear. All 10,000 women were screened for cervical cancer using a smear test. 1,000 of these women had an abnormal smear. As part of the trial, all 10,000 women also underwent a colposcopy and biopsy. The biopsy showed premalignant and malignant lesions in 500 patients. 50 of those women who had premalignant and malignant lesions on histology did not have a positive smear test. Which term accurately describes the 50 women?

A study on pulmonary embolism shows 10 patients out of 100 died who did not get treatment and 10 patients out of 100 died who got proper treatment. What is the absolute risk for the patient’s receiving proper treatment?

A case-control study looks at the risk of strokes in 145 men where some of them were smokers. Below are the results of the study:

What is the odds ratio of developing stroke in men who smoke?

The number needed to treat for the use of a new antiplatelet for management of stroke is 21. What is the definition of the number needed to treat?

This is the likelihood of a test reporting positive when the condition being tested is actually present. What is the SINGLE most likely term?

A new drug called “Zeetop” is undergoing clinical trials for the prevention of ischaemic strokes in patients with hyperlipidaemia. The trial looks at the incidence of ischaemic strokes within a 10 year period. The following is the data obtained from the study:

What is the relative risk reduction?

A screening test in the form of a questionnaire is being used to pick up patients with depression attending their GP appointments. The total score is 100. Patients who scored 82 or more were thought to have symptoms of depression and were offered further appointments to diagnose this. This screening test has a sensitivity of 0.84. What is the interpretation of the sensitivity given?

A new drug called “Zeeper” is undergoing clinical trials for the prevention of myocardial infarction in patients with type 2 diabetes mellitus. The trial looks at the incidence of myocardial infarction within a 5 year period. The following is the data obtained from the study:

What is the relative risk reduction?

A study on adherence to a depot antipsychotic in people with schizophrenia was carried out. The study had two groups of schizophrenic patients, group A and group B. Financial incentives were given to people in group A to encourage adherence to the medication. No incentives were given to people in group B. The study showed that patients in group A showed more adherence compared to group B. What is the SINGLE most appropriate study design for this?

There are 500,000 people who live in Peavile. In the past 5 years, there have been a total of 250 deaths in relation to a new strain of coronavirus. What is the mortality rate of this new strain of coronavirus in Peavile expressed per 1,000,000 individuals per year?

60 people are reported to be infected with the Hendra virus in a certain town. A short time later in this town, 20 new cases are announced, 20 people with this infection are pronounced deceased and 20 previously infected individuals are now cured. The current population of this town is 1000. What is the current prevalence of the Hendra virus in this town?

A clinical trial is comparing drug A to patients on placebo to prevent myocardial infarction in patients above age 60 years in a 10 year period. 20 patients needed to be treated with drug A to prevent one myocardial infarction over a 10 year period. 1 out of every 10 patients had nausea as a side effect when taking drug A. What is the number needed to treat for drug A in a 10 year period?

178 women with hypertrophic cardiomyopathy were recruited in a study. Half of these women were given drug A and the other half were given drug B by the researchers. They were followed up every 3 months from 2010 to 2020 to evaluate their condition. What is the SINGLE most likely type of clinical study in this scenario?

A randomized control trial was conducted to test the efficacy of an antidepressant drug called VFX. Group A received the drug, and the control group received a placebo. The results revealed a p-value> 0.1. What is the significance of such a finding?

A study of a new drug to decrease the risk of a myocardial infarction shows the following results:

1. 100 out of 1000 patients on the placebo drug developed a myocardial infarction in 5 years.
2. 50 out of 1000 patients on the new drug developed a myocardial infarction in 5 years.

What is the absolute risk reduction in a 5 year period in this study?

A double-blind study was designed to test the efficacy of a drug. One group of patients consisting of 898 people were given a placebo drug and the other group of patients consisting of 701 were given the active drug. Both groups were to be followed up for one year. Halfway through the trial, 25% of participants in the placebo group dropped out of the study and 3% of participants taking the active drug dropped out of the study. What is the SINGLE best explanation for this occurrence?

In a study to detect the efficacy of a new screening method to detect breast cancer, a new imaging technique named Szechnetium scan was tested on 1000 women. 200 of those who were scanned came back with features suggestive of malignancy. Upon further tissue biopsy, 170 of them were confirmed to be malignant. Only 20 out of those who came back negative using the scan developed cancer later. What is the positive predictive value for the new scanning method?

A study has been conducted which showed that 29 post-MI patients needed to be treated with aspirin to prevent one myocardial infarction (MI). The 95% confidence interval is 20-38. What is the correct interpretation of this data?