Cognitive biases in differential construction — MCQs

A group of neurologists develop a new blood test for Alzheimer's. They are optimistic about the test, as they have found that for any given patient, the test repeatedly produces very similar results. However, they find that the new test results are not necessarily consistent with the gold standard of diagnosis. How would this new test most accurately be described?

A 33-year-old man is brought by ambulance to the emergency room after being a passenger in a motor vehicle accident. An empty bottle of whiskey was found in his front seat, and the patient admits to having been drinking all night. He has multiple lacerations and bruising on his face and scalp and a supportive cervical collar is placed. He is endorsing a significant headache and starts vomiting in the emergency room. His vitals, however, are stable, and he is transported to the CT scanner. While there, he states that he does not want to have a CT scan and asks to be released. What is the most appropriate course of action?

A researcher is trying to determine whether a newly discovered substance X can be useful in promoting wound healing after surgery. She conducts this study by enrolling the next 100 patients that will be undergoing this surgery and separating them into 2 groups. She decides which patient will be in which group by using a random number generator. Subsequently, she prepares 1 set of syringes with the novel substance X and 1 set of syringes with a saline control. Both of these sets of syringes are unlabeled and the substances inside cannot be distinguished. She gives the surgeon performing the surgery 1 of the syringes and does not inform him nor the patient which syringe was used. After the study is complete, she analyzes all the data that was collected and performs statistical analysis. This study most likely provides which level of evidence for use of substance X?

A 25-year-old man comes to the physician for severe back pain. He describes the pain as shooting and stabbing. On a 10-point scale, he rates the pain as a 9 to 10. The pain started after he lifted a heavy box at work; he works at a supermarket and recently switched from being a cashier to a storekeeper. The patient appears to be in severe distress. Vital signs are within normal limits. On physical examination, the spine is nontender without paravertebral muscle spasms. Range of motion is normal. A straight-leg raise test is negative. After the physical examination has been completed, the patient asks for a letter to his employer attesting to his inability to work as a storekeeper. Which of the following is the most appropriate response?

Two studies are reviewed for submission to an oncology journal. In Study A, a novel MRI technology is evaluated as a screening tool for ovarian cancer. The authors find that the mean survival time is 4 years in the control group and 10 years in the MRI-screened group. In Study B, cognitive behavioral therapy (CBT) and a novel antidepressant are used to treat patients with comorbid pancreatic cancer and major depression. Patients receiving the new drug are told that they are expected to have quick resolution of their depression, while those who do not receive the drug are not told anything about their prognosis. Which of the following describes the likely type of bias in Study A and Study B?

A pharmaceutical corporation is developing a research study to evaluate a novel blood test to screen for breast cancer. They enrolled 800 patients in the study, half of which have breast cancer. The remaining enrolled patients are age-matched controls who do not have the disease. Of those in the diseased arm, 330 are found positive for the test. Of the patients in the control arm, only 30 are found positive. What is this test’s sensitivity?

A study is conducted in a hospital to estimate the prevalence of handwashing among healthcare workers. All of the hospital staff members are informed that the study is being conducted for 1 month, and the study method will be a passive observation of their daily routine at the hospital. A total of 89 medical staff members give their consent for the study, and they are followed for a month. This study could most likely suffer from which of the following biases?

A 27-year-old woman is brought to the physician by her parents because they are concerned about her mood. They say that she has “not been herself” since the death of her friend, who was killed 3 weeks ago when the fighter jet he piloted was shot down overseas. She says that since the incident, she feels sad and alone. She reports having repeated nightmares about her friend's death. Her appetite has decreased, but she is still eating regularly and is otherwise able to take care of herself. She does not leave her home for any social activities and avoids visits from friends. She went back to work after taking 1 week off after the incident. Her vital signs are within normal limits. Physical examination shows no abnormalities. On mental status examination, she appears sad, has a full range of affect, and is cooperative. In addition to taking measures to evaluate this patient's anxiety, which of the following is the most appropriate statement by the physician at this time?

A 77-year-old female comes to a medical school's free clinic for follow-up examination after a urinary tract infection (UTI) and is seen by a fourth year medical student. The clinic serves largely uninsured low-income patients in a New York City neighborhood with a large African American and Latino population. Two weeks ago, the patient was treated in the local emergency department where she presented with altered mental state and dysuria. The medical student had recently read about a study that described a strong relationship between cognitive impairment and UTI hospitalization risk (RR = 1.34, p < 0.001). The attending physician at the medical student's free clinic is also familiar with this study and tells the medical student that the study was conducted in a sample of upper middle class Caucasian patients in the Netherlands. The attending states that the results of the study should be interpreted with caution. Which of the following concerns is most likely underlying the attending physician's remarks?

A 57-year-old man presents to the emergency department for weight loss and abdominal pain. The patient states that he has felt steadily more fatigued over the past month and has lost 22 pounds without effort. Today, he fainted prompting his presentation. The patient has no significant past medical history. He does have a 33 pack-year smoking history and drinks 4 to 5 alcoholic drinks per day. His temperature is 99.5°F (37.5°C), blood pressure is 100/58 mmHg, pulse is 100/min, respirations are 17/min, and oxygen saturation is 98% on room air. On physical exam, you see a patient who is very thin and appears to be pale. Stool fecal occult blood testing is positive. A CT scan of the abdomen is performed demonstrating a mass in the colon with multiple metastatic lesions scattered throughout the abdomen. The patient is informed of his diagnosis of metastatic colon cancer. When the patient conveys the information to his family he focuses his efforts on discussing the current literature in the field and the novel therapies that have been invented. He demonstrates his likely mortality outcome which he calculated using the results of a large multi-center study. Which of the following is this patient most likely demonstrating?