A randomised controlled trial is conducted comparing a new medication or placebo for recovery from a certain illness.
What term best describes the probability of obtaining a result by chance at least as extreme as the one that was observed, assuming that the null hypothesis of no difference between the medication and placebo is true?
A 28-year-old patient who is participating in a clinical trial comes to your clinic for a flu shot. He is uncertain if it is permitted while he is in the trial, so his trial coordinator is consulted. The coordinator explains that the patient is part of a study involving 150 participants to evaluate the effectiveness and adverse effects of a new allergy medication, and receiving the vaccine should not be an issue.
What phase of the clinical trial is the 28-year-old patient in?
A trial is conducted to evaluate the effectiveness of a new screening test for detecting heart disease in patients over the age of 50. The contingency table below shows the results for a group of patients who were tested:
Heart disease present Heart disease absent
Test positive 120 15
Test negative 10 255
What is the positive predictive value of the new screening test for detecting heart disease (rounded to 2 decimal places)?
A new type of blood test is being studied that may accurately detect the presence of a certain disease in elderly patients. One hundred and fifty patients who have the disease confirmed via the gold standard, a specific medical test, are recruited, along with one hundred and fifty patients who do not have the disease. They are all subjected to the new blood test and the results are as follows:
Disease present on medical test Disease absent on medical test
Blood test positive 90 30
Blood test negative 60 120
What is the positive predictive value?
A new medication aimed at preventing outbreaks of shingles is being tested in clinical trials. One hundred participants are administered the new medication. Over a three-month period, 10 of the participants experience a shingles outbreak. Meanwhile, in the control group, 300 participants are given a placebo. During the same time frame, 50 individuals in the control group experience a shingles outbreak. What is the relative risk of experiencing a shingles outbreak while taking the new medication?
A 32-year-old woman with a body mass index of 51 kg/m2 presents to you seeking guidance on weight management, including the use of medication. You recently reviewed a systematic review of RCTs comparing orlistat to placebo for weight management, which included an asymmetrical funnel plot. What type of bias could this indicate?
An academic researcher is investigating the efficacy of a new treatment for elderly patients with osteoporosis. Prior to commencing her own study, she intends to conduct a meta-analysis to consolidate existing findings on the subject. As part of her meta-analysis, she must evaluate whether publication bias exists in the literature.
What is the most effective method for the researcher to detect this?
A new rapid diagnostic test is developed to diagnose Alzheimer’s disease. The test is based on measurement of certain biomarkers in the blood that are associated with the disease. The sensitivity and specificity of the test is 80% and 85%, respectively.
What is the likelihood ratio for a negative test result?
You are evaluating a study on the use of masks in public places to reduce viral upper respiratory tract infections among elderly individuals. The study found that the treatment group, who wore a mask, had fewer cases compared to the control group who did not wear a mask. The absolute risk in the control group was 0.5 whereas the absolute risk in the treatment group was 0.3.
What is the number needed to treat for elderly individuals in this study?
A research study examines the advantages of incorporating a new antiplatelet medication with aspirin after a heart attack in patients over the age of 60. The study yields the following outcomes:
Percentage of patients experiencing
another heart attack within 3 months
Aspirin 5%
Aspirin + new drug 3%
What is the number needed to treat to prevent one patient over the age of 60 from having another heart attack within 3 months?