20Competencies/Health Care/Biostatistics
C Positive predictive value
The positive predictive value indicates how often a patient has a disease given a positive test result. (A) The sensitivity indicates how often a test will be positive if a person has a disease. (B) The specificity indicates how often a test will be negative if a person does not have a disease. (D) The negative predictive value indicates how often a patient does not have a disease given a negative test result.
A Selection and placebo effect biases
The goal of randomization is to minimize selection bias, which occurs when subjects are included in a study in a nonrandom fashion. The goal of single blinding is to minimize the placebo effect, which occurs when a treatment improves a patient’s condition simply because he has the expectation that the treatment will help. (B) Observer bias (interviewer bias) occurs when a researcher intentionally or unintentionally pays more attention or provides more weight to one type of response or treatment. (C) Design bias occurs when the case and control groups are not matched properly. (D) Definition bias describes a lack of clarity of the concepts used in and goals of the study.
E Unprofessional behavior during medical school
Multiple recent studies have demonstrated a very strong association between medical school unprofessional behavior and subsequent disciplinary actions during the career of a physician. (A–D) These factors are much weaker predictors of future disciplinary actions.
A Sort, Assess, Lifesaving interventions, and Treatment/Transport
The SALT algorithm prioritizes the concept of triage. Patients should be triaged first, and then resources should be allocated and lifesaving procedures performed accordingly.
A Immediate, delayed, minimal, expectant
In a mass casualty scenario, the Centers for Disease Control and Prevention recommends triaging casualties into four categories. The lives of Category 1 patients with a red triage tag and “immediate” or “T1 priority” designation are in immediate danger and require immediate treatment. The lives of Category 2 patients with a yellow triage tag and “delayed” or “T2 priority” designation are not in immediate danger and will require urgent but not immediate medical care. Category 3 patients with a green triage tag and “minimal” or “T3 priority” designation have minor injuries but eventually will require treatment. Category 4 patients with a black triage tag and “expectant” or “no priority” designation are either dead or have very severe injuries precluding survival with the limited available resources.
B Identifying the characteristics of successful performance
The positive deviance theory focuses on identifying the attributes of successful performance and replicating these attributes in similar scenarios.
A Inform the family of the mistake, complete the procedure at the correct level, and inform the risk management team.
Informing the patient and family of anything that has gone wrong during a surgery is proper patient care and even may help to decrease liability. Most experts also agree that acknowledging the mistake will lead to a better trust relationship between the physician and the patient and family. Although the next most appropriate course of action in this situation is debated, after full disclosure and if the patient’s family agrees, completing the surgery is an option that should be considered to relieve symptoms and eliminate the need for further surgeries. It always is a good idea to contact the risk management team in such situations for advice on how to proceed following surgery.
D It is not unreasonable to perform the procedure, but there are limited data to endorse it.
This table summarizes the levels and classes of evidence.
A Stark law
The Stark law (also known as the physician self-referral law) prohibits physicians from referring patients to institutes in which they or a close family member have financial interests. (B) The federal anti-kickback statue prevents physicians from receiving compensation in exchange for using specific instruments or prescribing specific drugs. (C) Antitrust law regulates the conduct and organization of businesses to promote fair competition for the benefit of consumers. (D) The false claim act is a federal law that imposes liabilities on people and companies that defraud governmental programs.
A Proceed with the donation.
The recently revised Uniform Anatomical Gift Act states, “In the absence of an expressed, contrary indication by the donor, a person other than the donor is barred from making, amending, or revoking an anatomical gift of a donor’s body or a part if the donor made an anatomical gift” [194.240.1]. In this situation, proceeding with the donation is the most appropriate course of action; however, it always is prudent to attempt to reconcile the wishes of the donor with those of the family. (E) Obtaining a court order to proceed with the donation is not necessary in this situation, but discussing the situation with the ethics committee might be a good option.
A Incidence: 1/3,200,000; prevalence: 1/50,000
The incidence of a disease is defined as the annual number of new cases (in this example, 100) out of the total population (320 million). The prevalence of a disease is defined as the total number of cases at a certain point in time (6,400) out of the total population (320 million). These ratios often are simplified to have a numerator of 1 or a denominator of 100,000.
B Randomized, single-blinded, prospective clinical study
This study is an example of a randomized, single-blinded, prospective clinical study. In the HEAT (Hydrogel Endovascular Aneurysms Treatment) trial, patients were randomly allocated to one of two groups, making the study randomized. The study was prospective, as patients were allocated to the groups prior to their procedures and were followed after their procedures. Because the patients did not know which type of coil they were receiving, and because the physicians did know, the study was single-blinded. Of note, in the actual trial, a blinded imaging core lab evaluated all imaging to minimize reporting bias.
C Interpersonal skills and communication
Interpersonal skills and communication skills refer to a resident’s ability to communicate effectively among colleagues in his and other specialties. It also refers to the ability of a resident to share his research and demonstrate leadership skills. (A) Patient care describes the ability to provide compassionate and effective health care. (B) Medical knowledge describes the ability to acquire and apply current medical knowledge and use advanced search engines to stay current on medical knowledge and data. (D) Practice-based learning and improvement describes the ability to appraise information critically on a daily basis and to analyze it in a way that improves patient care. (E) Systems-based practice describes multidisciplinary approaches to patient care and the ability to optimize care by involving multiple teams in patient management.
B Federal anti-kickback statute
The federal anti-kickback statue prevents physicians from receiving compensations for using or prescribing specific instruments or drugs. (A) The Stark law (also known as the physician self-referral law) prohibits physicians from referring patients to institutes in which they or a close family member have financial interests. (C) Antitrust law regulates the conduct of organizations and businesses to promote fair competition for the benefit of consumers. (D) The false claim act is a federal law that imposes liabilities on people and companies who defraud governmental programs.
A Reliable
Reliability is an evaluation of random error. Reliability is maximal when a test gives similar results on repeat measurements (has high precision). (B, C) Validity and accuracy are defined as the ability of a test to measure a given outcome. Accuracy is determined by comparing data from a test to a predefined gold standard. (D, E) Sensitivity and specificity are obtained by comparing test results to a gold standard.
D The sample size in the second study is small.
The lack of statistical significance in the second study (the 95% confidence interval includes the value of 1) is secondary to the study being underpowered with a small sample size. We know from the first study that there is an association between smoking and atherosclerosis; therefore, increasing the sample size in the second study should lead to the same result. (A) The first study is statistically significant, as the 95% confidence interval does not include the null value of 1. (B) Bias cannot be assessed from the information. (C) Accuracy cannot be assessed from the information. (E) The sample size in the first study is adequate, as the study has reached statistical significance with a 95% confidence interval that does not include the value of 1.
A ANOVA
The analysis of variance (ANOVA) test is used to compare two or more independent, quantitative, continuous, normal variables. An example of its use would be when answering the question “Are neurosurgery board exam scores different between residents who have read one, two, or three Thieme review books?” (B) The Student (unpaired) t-test is used to analyze one continuous, normal variable in two groups. It could be used when answering the question “Is there a difference in the resting heart rates of diabetics compared with nondiabetics?” (C) The paired t-test is used to analyze one continuous, normal variable in two groups. It often is used when data are being evaluated pre- and post-treatment. It could be used when answering the question “How do the heart rates of diabetics differ before and after using an antihypertensive?” (D) The chi-square test compares one independent variable in two independent groups of the categorical type. For example, it would be used to answer the question “Is the distribution of gender and drinking behavior due to chance, or is there a statistical significant difference?” (E) The Fisher exact test compares one independent variable in two independent groups of the categorical type; it works well for small sample sizes. It provides an exact p value instead of estimating a p value (the latter needed as groups move toward infinity); therefore, it is more accurate than the chi-square test.
A Equipoise
Equipoise provides the ethical basis for medical research. It means that there is genuine uncertainty within the expert medical community about whether the treatment will be beneficial. Patients with large posterior fossa hemorrhages most likely will die if they are not surgically treated; therefore, it is unethical to randomize such patients to the two groups and withhold the known therapy. (B) Autonomy refers to the capacity to think, decide, and act based on one’s own free initiative. The patients with the hemorrhages most likely will be unable to make decisions regarding their care, but this is true regardless of their enrollment in the study. (C) Nonmaleficence is the principle of do no harm. (D) Justice is to account for limited resources by justly allocating resources. (E) Disclosure refers to making patients aware of the risks of surgery and nonoperative care. This would have to be done prior to enrollment in any such trial.
C Practice-based learning and improvement
Practice-based learning and improvement describes the ability to appraise information critically on a daily basis and to analyze it in a way that improves patient care. (A) Patient care describes the ability to provide compassionate and effective health care. (B) Medical knowledge describes the ability to acquire and apply current medical knowledge and use advanced search engines to stay current on medical knowledge and data. (D) Systems-based practice describes multidisciplinary approaches to patient care and the ability to optimize care by involving multiple teams in patient management. (E) Professionalism describes the ability to demonstrate the principles of ethical behavior.
D 4%
Posttest probability is the probability that a patient has or does not have the disease after obtaining test results. In this case, the question is asking for the negative predictive value (NPV). The NPV depends on the prevalence of the disease in a tested population and can be calculated using the formulas given below. The NPV expresses the probability of the patient not having the disease following a negative test. In this situation, the probability of the patient not developing Alzheimer disease is 96%, giving him a 4% chance of developing the disease.
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