A screening test for a disease is performed on 1000 people over the age of 50. A total of 888 people do not have the disease. Of those with the disease, 100 had a positive screening test result. A total of 890 patients had a negative screening test result.
What is the specificity of the screening test?
A screening test for a disease is performed on 1000 people. A total of 888 people do not have the disease. Of those with the disease, 100 had a positive screening test result. A total of 890 patients had a negative screening test result.
What is the positive predictive value of the screening test?
You are evaluating the accuracy of a new blood test to diagnose ulcerative colitis in elderly patients and come across a study that analyzed its use in 200 individuals, ten of whom were histologically diagnosed with the condition. According to the study, the blood test correctly identified seven patients as positive and 188 patients as negative. What is the sensitivity of this blood test for diagnosing ulcerative colitis in elderly patients in this study?
What study design would be most useful in testing the hypothesis that metal industry workers are more likely to develop a rare neurological disorder due to exposure to a particular type of heavy metal residue, given that the prevalence of the disease is 1 in 1,000,000?
A pharmaceutical company wishes to conduct a study on the effect of a new drug on the survival rates of elderly patients with malignant melanoma.
Which one of the following is considered the gold standard experimental study design to assess the effect of an intervention on a variable of interest (eg survival)?
A study is conducted to identify the risk factors associated with the development of Alzheimer’s disease before the age of 60 years. A group of 100 patients with Alzheimer’s disease <60 years of age is compared to a group of 80 age- and gender-matched individuals without Alzheimer's disease. The table of odds ratios for four studied risk factors is given below:
Ratio/confidence Age Family history Educational level History of head trauma
Odds ratio 4.5 3.5 0.5 1.6
95% confidence interval 0.5-8.5 1.5-5.5 0.3-1.1 1.2-2.0
What is the most significant risk factor identified in this study?
A 67-year-old man attends for his first abdominal aortic aneurysm screening. He is found to have an asymptomatic abdominal aortic aneurysm measuring 5.3 cm. He is seen routinely by a regional vascular centre that made the decision not to perform an elective repair. He has been advised to stop smoking, reduce his blood pressure through antihypertensive medications and to attend surveillance appointments.
How often should the patient receive surveillance abdominal ultrasounds?
A local guideline on use of drugs in palliative care includes the following statement:
‘Haloperidol is effective in relieving nausea in patients with end-stage renal failure and should be considered the first-line agent in these patients.’
The guideline states that this recommendation is based on Level 3 evidence.
Which statement best describes the type of evidence that supports this recommendation if the patients are elderly?
A study is conducted to compare the efficacy of a new blood test for detecting respiratory tuberculosis (TB) infection, in comparison to the current gold standard investigation of sputum microscopy. The study involves 312 patients with suspected TB. During the study, sputum microscopy is not available for 20 of the patients, resulting in them only having the new blood test. With regards to age, what bias is this study most susceptible to?
Researchers conducted a case-control study examining the relationship between poor diet and coronary artery disease. They enrolled cases from cardiac wards in hospitals and controls from General Practice surgeries in a single city. Diet for the past 5 years was assessed using an in-person interview in the setting where the patients were enrolled. After conducting the study, researchers found that, on average, the dietary interview with cases lasted 20 minutes longer than the interview with controls. In addition, the information collected from cases was much more detailed.
Which type of bias has most likely occurred?