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Question 1 of 40
1. Question
A study evaluated predictors of adverse outcomes in geriatric patients admitted to the hospital with a hip fracture requiring surgery. The study compared an old multidimensional score (Model 1) with a new classification system (Model 2). The following results were reported:
AUC = area under the curve
Which of the following is the best statement about the study results?
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Question 2 of 40
2. Question
A randomized controlled trial is conducted to evaluate the safety and efficacy of monotherapy with a new disease-modifying antirheumatic drug (DMARD) after switching from methotrexate versus continuing methotrexate in patients with inadequate response to methotrexate. The study enrolled adults (age ≥18) who fulfilled the American College of Rheumatology (ACR)–European League Against Rheumatism (EULAR) classification criteria for rheumatoid arthritis. The investigators defined monotherapy with the new DMARD as effective if the treatment resulted in a 20% improvement in the ACR criteria (ACR20) at week 14. In designing the study, the researchers set the probability of wrongly finding that DMARD monotherapy after switching from methotrexate is more effective than continuing methotrexate as 1%, and they set the probability of wrongly finding that the effectiveness of the two therapies is the same as 5%. Which of the following is the most accurate estimate of the statistical power in this study?
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Question 3 of 40
3. Question
A large-scale clinical trial is being planned to evaluate the effect of a nonselective beta blocker, propranolol, on the clinical course of portal hypertension. The comparison is with placebo. The primary outcomes of the study are all-cause mortality and major gastrointestinal hemorrhage. Secondary outcomes are minor gastrointestinal hemorrhage and the number of hospitalizations. Classification of the episodes of gastrointestinal hemorrhage into “major” and “minor” is based on clinical assessment as well as laboratory data such as change in hemoglobin level. The investigators are concerned about the possibility that major gastrointestinal hemorrhage events could be over-reported in the placebo group. Which of the following is the most useful technique to reduce this possibility?
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Question 4 of 40
4. Question
The Department of Health Services and Public Health authorities investigated an outbreak of severe gastrointestinal (GI) illness in Bayamón, Puerto Rico. A total of 25 individuals had been admitted to the city hospital with acute diarrhea, vomiting, bloating, and severe abdominal pain. A standardized questionnaire was used to collect relevant information related to person, place, and time from 25 individuals with severe GI illness and 75 individuals matched by age and sex who had been admitted to the same hospital for any reason other than GI illness. Preliminary results showed that 96% of the individuals with severe GI illness had eaten at a popular local restaurant 2-4 days before, and 4% of the individuals without GI illness had eaten at the same restaurant during the same period. Which of the following statements is correct about this study design?
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Question 5 of 40
5. Question
Case reports indicate that exposure to manganese among miners may lead to central nervous system damage, particularly a Parkinson-like syndrome. This syndrome, thought to be associated with increased mortality, is characterized by cogwheel rigidity, neuropsychiatric and cognitive manifestations, balance and speech changes, dystonia more pronounced than that seen with Parkinson disease, and resting tremors less pronounced than those seen with Parkinson disease. A group of investigators are further investigating the association between exposure to manganese and increased mortality among miners. As part of their statistical analysis, they calculate a standardized mortality ratio of 1.75 among manganese miners compared to the general population. Which of the following statements is most applicable to this study result?
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Question 6 of 40
6. Question
A cross-sectional study is investigating the association between smoking and latent tuberculosis infection (LTBI) in adults age ≥21 in a rural community. Interferon-γ release assay (IGRA) results are used to determine LTBI status; subjects with a positive IGRA result undergo chest x-ray to exclude active pulmonary tuberculosis. Sociodemographic, lifestyle, and health-related information are collected by a standardized questionnaire administered by trained interviewers. The reported results on IGRA positivity among smokers are as follows:
Which of the following factors strongly suggests a potential causal relationship between smoking and LTBI?
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Question 7 of 40
7. Question
A 69-year-old man with chronic kidney disease comes to the office to discuss options for dialysis. The patient wishes to choose the dialysis modality that will allow him to live the longest. The following Kaplan-Meier survival curve is obtained from a prospective study on the survival of 1800 patients who began dialysis with either hemodialysis (HD) or peritoneal dialysis (PD) and were followed for 5 years. The event of interest was death while on dialysis.
Based on the findings of this study, which dialysis option offers improved survival?
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Question 8 of 40
8. Question
A follow-up study was conducted to assess the effect of circumcision on the incidence of penile carcinoma. A large cohort was investigated. The rate in uncircumcised males was 8/1000, and the rate in circumcised males was 6/1000. The investigators concluded that circumcision may be markedly effective in reducing the incidence of the disease in the population. According to the study results, how many patients should be circumcised to prevent one case of penile carcinoma?
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Question 9 of 40
9. Question
A case-control study evaluated the association between long-term use of a heartburn medication and bladder and colon cancer. The study enrolled 130 patients with bladder cancer, 130 patients with colon cancer, and 230 patients matched by age and sex with no history of cancer. All study participants were interviewed and their medical records reviewed for past long-term use of the heartburn medication. Long-term use of the heartburn medication was found in 30 (23.1%) patients with bladder cancer, in 28 (21.5%) patients with colon cancer, and in 30 (13.0%) patients with no history of cancer. Based on these results, which of the following is the closest interpretation of the odds ratio (OR) of long-term use of the heartburn medication in patients with bladder cancer relative to patients with no history of cancer?
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Question 10 of 40
10. Question
A 16-month-old boy is brought to the pediatrician by his parents for a follow-up visit. The patient was recently diagnosed with a rare genetic disorder that causes severe neurodegeneration in infants. In the past 5 years, a total of 34 cases of this rare genetic disorder had been diagnosed in the US. The exact underlying cause for the disorder is unknown. The parents want to know the prognosis for their son compared to children of the same age who do not have the disorder. Which of the following types of study designs would be the most appropriate for answering the parents’ question?
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Question 11 of 40
11. Question
A 32-year-old woman, gravida 2 para 1, comes to the office for a routine prenatal visit. The patient had a postpartum hemorrhage (PPH) after her first pregnancy and is worried about the possibility of PPH after her scheduled repeat cesarean delivery. She read about the effectiveness of prophylactic tranexamic acid in reducing the risk of hemorrhage after scheduled cesarean delivery and wants to discuss the results. The outcomes of the study were PPH, clinical and laboratory (blood samples at day 2) measurements of postpartum blood loss, and several adverse events after scheduled cesarean delivery at ≥34 weeks gestation. Patients received intravenous infusion of a uterotonic agent and either tranexamic acid or saline placebo within 3 minutes after cesarean delivery. A summary of the results is shown in the table below.
Tranexamic
acid groupPlacebo group
RR
95% CI
Postpartum outcomes PPH: no./total no. (%) 556/2086
(26.7)653/2067
(31.6)0.840
0.767-0.928
Clinically significant PPH according to health care providers: no./total no. (%) 303/2220
(13.6)327/2208
(14.8)0.922
0.797-1.065
Additional uterotonic agents for excessive bleeding: no./total no. (%) 130/2217
(5.9)159/2206
(7.2)0.814
0.650-1.018
Blood transfusion: no./total no. (%) 42/2221
(1.9)39/2208
(1.8)1.071
0.695-1.649
Hemoglobin - Peripartum decrease >2 g/dL: no./total no. (%)
397/2088
(19.0)497/2071
(24.0)0.790
0.705-0.891
Hematocrit - Peripartum decrease >10 percentage points: no./total no. (%)
66/2086
(3.2)93/2071
(4.5)0.705
0.517-0.959
CI = confidence interval; RR = relative risk; PPH = postpartum hemorrhage. *Adjusted risk ratios were estimated using Poisson mixed-effects regression models with systematic adjustment for randomization stratification variables (center and timing of cesarean delivery [before or during labor]).
Based on the study results, which of the following conclusions is strongly justified?
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Question 12 of 40
12. Question
A 46-year-old man comes to the office due to loose teeth and inflammation in his gums. After periodontal evaluation, a diagnosis of localized aggressive chronic periodontitis is suspected. Laboratory results, including C-reactive protein (CRP) results, are pending. If serum CRP levels in patients with aggressive chronic periodontitis are known to be normally distributed with mean 6 mg/dL and standard deviation 1 mg/dL, what is the probability that this patient has a CRP >8 mg/dL?
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Question 13 of 40
13. Question
A group of researchers conducted a study to identify risk factors for death after coronary artery bypass graft (CABG) surgery. Individuals who had undergone CABG and who are enrolled in a cohort study represent the source population for the new study. A random sample of 150 of these individuals was selected; they were initially classified as diseased (dead) or nondiseased (alive) based on death following CABG. Diseased and nondiseased subjects were matched for age and gender. The frequency of several risk factors was subsequently compared between the diseased and nondiseased groups. Study results showed that diabetes, cigarette smoking, peripheral vascular disease, lengthy hospitalization, and elevated triglycerides, total cholesterol, C-reactive protein, and high-density lipoprotein cholesterol were significantly associated with death following CABG. Which of the following best describes the study design?
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Question 14 of 40
14. Question
An epidemiologic study is conducted to evaluate the long-term complications of coronary stent placement. 10,000 patients who underwent emergency or elective percutaneous coronary intervention at tertiary care centers around the nation were randomly selected and monitored for the development of adverse events. According to the study results, 2% of patients who received bare metal stents developed stent thrombosis within a year. 40% of the patients who developed stent thrombosis died as a result. The risk of death in a patient who develops stent thrombosis is best described by which of the following epidemiologic parameters?
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Question 15 of 40
15. Question
Several tests have been developed to measure the serologic markers of breast cancer. These tests have different specificities and sensitivities for the early stage of breast cancer. If positive, which of the following tests will have the highest positive predictive value for the disease, assuming a prevalence of 10%?
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Question 16 of 40
16. Question
Title
Effect of support systems during and after pregnancy on the development of postpartum depression (PPD).
Objective
To study the association between support system during and after pregnancy and the development of PPD.
Methods
Design: Prospective cohort study.
Follow-up period: 24 months.
Participants: Women age ≥21 in the first trimester of pregnancy.
Exposure: Support system (good or poor) during and after pregnancy.
Outcome measure: Incidence of PPD.
Results
Data analysis revealed that women with a good support system had a significantly lower incidence of PPD than women with a poor support system (p <0.01). An excerpt of the study results is shown below.
Incidence of PPD*
Women who had a good
support system (n = 1,500)6%
Women who had a poor
support system (n = 3,500)36%
*p <0.01.
Conclusion
The researchers concluded that having a poor support system during and after pregnancy may significantly increase the risk of developing PPD.
The abstract shown on the left applies to the next 2 items.
Physician-researchers at a women’s health clinic that caters to an underserved population are reviewing the results of a study they conducted regarding the effect of support systems during and after pregnancy on the development of postpartum depression.
Item 1 of 2
Based on the results of the study, what was the approximate incidence of postpartum depression regardless of type of support system?
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Question 17 of 40
17. Question
Title
Effect of support systems during and after pregnancy on the development of postpartum depression (PPD).
Objective
To study the association between support system during and after pregnancy and the development of PPD.
Methods
Design: Prospective cohort study.
Follow-up period: 24 months.
Participants: Women age ≥21 in the first trimester of pregnancy.
Exposure: Support system (good or poor) during and after pregnancy.
Outcome measure: Incidence of PPD.
Results
Data analysis revealed that women with a good support system had a significantly lower incidence of PPD than women with a poor support system (p <0.01). An excerpt of the study results is shown below.
Incidence of PPD*
Women who had a good
support system (n = 1,500)6%
Women who had a poor
support system (n = 3,500)36%
*p <0.01.
Conclusion
The researchers concluded that having a poor support system during and after pregnancy may significantly increase the risk of developing PPD.
Item 2 of 2
The researchers found that women with a poor support system had a statistically significant greater chance to develop postpartum depression than women with a good support system. If poor support system is the exposure of interest, which of the following represents the most likely measure (ie, odds ratio [OR] or relative risk [RR]) and magnitude of the effect and corresponding 95% confidence interval (CI)?
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Question 18 of 40
18. Question
A group of rheumatologists wants to study the association between past use of procainamide for the treatment of arrhythmias and drug-induced lupus. The rheumatologists plan to conduct a case-control study to evaluate the association. Which of the following corresponds with the proposed study design?
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Question 19 of 40
19. Question
A group of biomedical researchers developed a diagnostic process that applies the same shortwave rays used in airport security scanners to distinguish cancerous skin lesions from normal skin. The technology uses millimeter-wave radiation, which bounces off different materials with quantifiable reflectivity signatures. The researchers found that cancerous tumors reflect more calibrated energy than normal skin; therefore, the technology identifies diseased tissue by detecting reflectivity hotspots. A preliminary evaluation of the performance of the diagnostic tool showed that 92% of all skin tissue samples with a positive test result were cancerous, and that 99% of all skin tissue samples with a negative test result were normal. Based on these preliminary data, which of the following is the most accurate interpretation of the results?
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Question 20 of 40
20. Question
A 42-year-old woman comes to the office for a routine follow-up. She was diagnosed with multiple sclerosis 3 months ago and has had no relapses since. She had previously preferred not to take any medications for multiple sclerosis, but she is now interested in finding out about different treatments. The patient has no other medical problems. She does not use tobacco, alcohol, or illicit drugs. Examination shows no abnormalities. A new treatment A is available that is apparently highly effective in preventing multiple sclerosis relapses. A randomized trial shows that the incidence of relapses was 20% after 6 months of treatment A. Patients managed with placebo had an incidence of 25% during the same time period. Considering this information, how many patients will need to be treated with treatment A in order to prevent 1 episode of relapse of multiple sclerosis during the first 6 months of therapy?
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Question 21 of 40
21. Question
A recent study evaluated the association between proton pump inhibitor (PPI) use and kidney failure. The investigators initially identified a group of individuals having ≥2 claims for an acute kidney injury (AKI) diagnosis and a group of individuals without claims for an AKI diagnosis. Once these groups were identified, the history of PPI use was recorded and compared between the groups. Study results showed that PPI use was positively associated with AKI even after controlling for potential confounding conditions. The structure of this study is most consistent with which of the following study designs?
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Question 22 of 40
22. Question
A 78-year-old Caucasian man with stage 3 chronic kidney disease and nonischemic cardiomyopathy is admitted to the hospital with pulmonary edema. A recent study used intravenous hydralazine and oral isosorbide dinitrate (ISDN) in patients with pulmonary edema. The study randomized 310 African American patients admitted with pulmonary edema into an intervention group (ISDN + hydralazine) and a usual care group. The mean left ventricular ejection fraction was 24%, and all patients had normal renal function. The study results showed the following:
Intervention group
Usual care
P-value
Improvement in distress at 1 hour
56%
40%
0.03
In-hospital mortality
2%
4%
0.40
Which of the following study features is most limiting in applying the study intervention to this patient?
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Question 23 of 40
23. Question
Glycine (Gly) has been implicated in several neurological disorders, including malignant brain tumors. However, the current approach to measuring Gly in the brain is not precise, primarily due to the spectral overlap with myo-inositol (mI). A novel approach to measuring Gly and mI in healthy and tumorous brains provides more reliable spectral differentiation between Gly and mI, such that alterations of Gly in brain tumors can now be evaluated more precisely. A group of researchers plans to conduct 2 parallel studies to measure and compare Gly levels among healthy and tumorous brains. Study A will use the current approach to measure Gly in the brain whereas study B will use the novel approach. All other factors being equal, which of the following statements is most likely true concerning these 2 studies?
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Question 24 of 40
24. Question
A study was conducted to identify factors associated with rebleeding in patients admitted to the hospital with upper gastrointestinal hemorrhage. The medical charts of 2,488 patients were analyzed retrospectively, and a logistic regression analysis was conducted to identify potential risk factors for rebleeding. An excerpt of study results is shown below.
Variables associated with rebleeding
Variable Odds
ratio95% confidence
intervalSex (female) 0.293
0.112-0.832
Helicobacter pylori infection (positive) 0.351
0.271-0.910
Hematochezia 2.467
1.037-6.712
Number of comorbidities 2.500
2.145-2.812
Endoscopic therapy with epinephrine injection only 6.846
1.761-25.246
Endoscopic therapy with thermal coagulation only 6.706
1.373-33.497
Combination endoscopic therapy (epinephrine injection + thermal coagulation) 2.453
1.071-5.641
No missing data points regarding the type of endoscopic therapy received, comorbidities, or Heliobacter pylori status were reported in the study. Which of the following is the best interpretation of the study results?
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Question 25 of 40
25. Question
A prospective randomized clinical trial was conducted with the primary goal of determining whether, in postmenopausal women who have undergone loop electrosurgical excision procedure (LEEP), regular cervical dilatation is effective for preventing cervical stenosis (CS). Women who met the study criteria were randomly allocated to the intervention group (cervical dilatation in the third, fifth, and eighth weeks after LEEP) or the control group (no intervention after LEEP). A colposcopic follow-up examination was performed 6 months after LEEP to determine the incidence of CS. A secondary goal of the study was to identify potential risk factors for CS in the control group. Logistic multiple regression analyses were used to calculate the odds ratios (ORs) to determine the risk factors for CS in the control group. Risk factors were measured quantitatively; therefore, the ORs represent the odds of CS associated with higher levels of the risk factor. An excerpt of study results is shown below.
Risk factor
Regression
coefficient (β)Standard error
Wald’s test
OR*
95% CI
Lower limit
Upper limit
Pathological grade 0.249
0.287
0.749
1.282
0.730
2.251
LEEP frequency 2.292
0.382
35.994
9.893
4.679
20.915
LEEP resection area 0.036
0.057
0.572
1.036
0.945
1.136
LEEP resection depth 0.125
0.045
7.856
1.133
1.038
1.236
*OR adjusted by age, duration of menopause, gravidity, parity, high-risk human papilloma virus, high-grade cervical intraepithelial neoplasia. β = regression coefficient for predictor variable; CI = confidence interval; LEEP = loop electrosurgical excision procedure; OR = odds ratio.
When other factors are controlled, which of the following is the most appropriate conclusion about these data?
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Question 26 of 40
26. Question
A study is conducted to compare an established breast imaging technique (EBIT) and a novel breast imaging technique (NBIT) with histopathological results and to compare the sensitivity, accuracy, and positive and negative predictive values for both imaging modalities. NBIT and EBIT examinations were performed in 102 patients who had suspicious lesions described in conventional mammography. All visible lesions were evaluated independently by 2 experienced radiologists using breast imaging reporting and data system (BI-RADS) classifications (scale 1–5). Dimensions of lesions measured with each modality were compared with postoperative histopathology results. The plot below shows the receiver operating characteristic (ROC) curves for NBIT and EBIT based on BI-RADS scores.
Based on the ROC curves, which of the following is the most appropriate conclusion?
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Question 27 of 40
27. Question
Researchers plan to conduct a randomized, double-blind, placebo-controlled, crossover trial to assess the efficacy of orally administered AKL1 (a botanical mixture in capsule form) in addition to standard asthma therapy. Adults with suboptimally controlled asthma despite current therapy will be recruited. The study will consist of the following 4 periods, during which subjects will continue their normal asthma treatments:
-
A 4-week single-blind baseline period, during which subjects will receive a placebo
-
A 12-week double-blind active treatment period, during which subjects will receive either AKL1 or placebo
-
An 8-week single-blind washout period, during which subjects will receive a placebo
-
A second 12-week double-blind active treatment period, during which subjects will be crossed over from ALK1 to placebo or vice versa.
Daily diaries will record key measurements: peak expiratory flow and symptoms; spirometry; validated symptom and health status questionnaire scores; and adverse events monitored at study visits. Based on this information, which of the following statements is most likely true?
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Question 28 of 40
28. Question
Two groups of investigators are interested in the problem of esophageal cancer in a population that has a high prevalence of hot beverage consumption. One group conducted study A, which showed that hot beverage consumption is associated with esophageal cancer, with an odds ratio (OR) of 1.51 and a 95% confidence interval of 1.19 to 1.81. The other group conducted study B, which demonstrated an OR of 1.46 and a 95% confidence interval of 0.95 to 1.97. Which of the following statements is most likely true concerning the results of these 2 studies?
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Question 29 of 40
29. Question
A randomized, double-blind, placebo-controlled trial is conducted to evaluate the effectiveness of two new drugs (A and B) for the secondary prevention of recurrent pericarditis. A total of 120 patients with a first recurrence of pericarditis were randomly assigned to Drug A, Drug B, or placebo in a 1:1:1 ratio. The primary outcome was recurrence rate at 18 months. An excerpt of study results is shown in the table below.
Treatment
Recurrence rate at 18 months
Absolute risk difference*
Drug A
0.350
0.250†
Drug B
0.475
0.125†
Placebo
0.600
–
*Compared to placebo.
† p < 0.05 for difference in risk.
The study reported no significant difference in the cost of treatment and adverse event profile with Drug A or Drug B for patients. Which of the following statements about the number needed to treat (NNT) for each drug is true based on these data?
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Question 30 of 40
30. Question
A study examined the role of a humanized monoclonal antibody (mAb) that binds soluble forms of amyloid in treating Alzheimer disease. Patients were randomly assigned to a mAb injection or placebo group for 14 months. The outcomes included changes in cognitive performance assessed by different scores at week 72 compared to baseline. Higher scores indicate worse impairment. The following numbers were reported for patients with mild and moderate Alzheimer disease.
Which of the following is the most accurate interpretation of these study results?
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Question 31 of 40
31. Question
Several clinical trials studied the effect of a new antiviral agent on symptomatic relief of genital herpes simplex virus infection. All trials were based on physician report of symptom improvement; valacyclovir was used as a comparator. The pooled analysis of studies that blinded only patients favored valacyclovir with an odds ratio for valacyclovir of 1.65 (95% confidence interval, 1.53-1.75). The pooled analysis of studies that blinded both patients and treating physicians favored the new agent with an odds ratio for valacyclovir of 0.64 (95% confidence interval, 0.38-0.79). Which of the following best explains the difference in the reported odds ratios?
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Question 32 of 40
32. Question
Gastric adenocarcinoma is typically diagnosed using upper endoscopy and managed with radical gastrectomy and, in some cases, chemoradiation; nevertheless, long-term survival is poor. Researchers in a region with a relatively high incidence of gastric adenocarcinoma are evaluating a novel screening test for early detection of the malignancy in high-risk patients. The novel test is based on the measurement of a recently discovered serologic marker of gastric adenocarcinoma, MGAc. Based on results of a large study sample of representative high-risk patients screened with MGAc and diagnosed with gastric adenocarcinoma, the mean survival of patients since time of diagnosis is 8.2 months. A review of records shows that, compared to these patients, similar high-risk patients who were diagnosed using the traditional endoscopic modality had a statistically significant lower mean survival of 7.1 months, with no statistically significant differences in the rates of radical gastrectomy or in the average number or intensity of chemoradiation cycles. Which of the following best explains these results?
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Question 33 of 40
33. Question
A non-inferiority study is conducted to assess a new anti-Xa inhibitor (drug A) in patients with atrial fibrillation. Warfarin is chosen as comparator. Study results are shown on the image below.
Which of the following best describes the effect of drug A in preventing myocardial infarction?
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Question 34 of 40
34. Question
A large study surveyed 24-hour dietary fiber intake in a nationally representative sample of the United States population. The investigators also collected anthropometric and laboratory data soon after survey completion. The following results were reported for prevalence of obesity, metabolic syndrome, and elevated inflammatory markers per quintiles of daily dietary fiber intake.
Which of the following is the best interpretation of the study results?
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Question 35 of 40
35. Question
Investigators want to explore a possible association between the use of nonsteroidal antiinflammatory drugs (NSAIDs) and the development of Crohn disease. They plan to administer a standardized questionnaire on NSAID use over the past year to patients with newly diagnosed Crohn disease and to age- and sex-matched healthy volunteers. The study design is most concerning for which of the following?
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Question 36 of 40
36. Question
A clinical trial was conducted to compare the effects of ACE inhibitors and diuretics in elderly patients with hypertension. The investigators believed that ACE inhibitors provide some additional survival benefits over diuretics use in elderly subjects because of their neurohumoral effects. The study lasted 5 years and the investigators presented the following results after the completion of the study:
ACE inhibitor
Diuretic
Hazard ratio (95% confidence interval)
Events
Rate per 1000
Events
Rate per 1000
All-cause mortality
190
15.5
210
17
0.90 (0.80-1.01)
Any non-fatal
cardiovascular event57
4.8
82
6.7
0.68 (0.45-0.96)
Heart failure
69
5.6
78
6.4
0.85 (0.62-1.18)
According to the information given, which of the following is the best interpretation of the study results?
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Question 37 of 40
37. Question
A phase 3, randomized controlled trial was conducted to evaluate the effect of Drug X and Drug Y on serum parathyroid hormone (PTH) concentrations in patients receiving hemodialysis with severe secondary hyperparathyroidism. A total of 508 patients were randomly assigned to Drug X or Drug Y after each hemodialysis session for 26 weeks. The primary efficacy endpoint was the percentage of patients achieving >30% reduction in mean PTH from baseline during weeks 20-27. A secondary efficacy endpoint was the percentage of patients achieving mean PTH <300 pg/mL. An excerpt of the study results is as follows:
Drug X
Drug Y
p-value
Primary efficacy endpoint
74.0%
85.4%
<0.001
Secondary efficacy endpoint
41.8%
49.6%
<0.001
Based on these results, which of the following is a possible 95% confidence interval for the difference in the percentage of patients who achieved the primary efficacy endpoint between Drug X and Drug Y?
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Question 38 of 40
38. Question
A randomized, double-blinded clinical trial was conducted to evaluate the effect of a new hypolipidemic drug on the survival of patients after percutaneous coronary intervention (PCI). 1000 patients undergoing PCI were randomly assigned to the drug or placebo group. 500 patients were in each group. The 2 groups were then followed for 3 years for the development of acute coronary syndromes. Severe acute myositis was reported as a rare side effect of the drug therapy, but the difference between the 2 groups in the occurrence of this side effect was not statistically significant (p = 0.09). A review of the literature shows that, in prior clinical trials and case reports, the same side effect was noted in some patients taking this drug. Which of the following is the most likely cause for the failure to detect a significant statistical difference in the occurrence of acute myositis between the treatment and placebo groups in this randomized trial?
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Question 39 of 40
39. Question
A large longitudinal study examined the association between obesity (defined as BMI >30 kg/m2) and risk of ischemic stroke in a cohort of patients. After assessing participant baseline characteristics, researchers followed 2,300 patients for a mean of 2.7 years and determined the incidence of major cardiovascular events. Within the entire cohort, the crude relative risk (RR) of ischemic stroke was 2.4 in obese patients as compared to nonobese patients, with a 95% confidence interval (CI) of 1.8-2.6. When the cohort patients were divided into those with diabetes mellitus and those without, among patients with diabetes, the RR of ischemic stroke was 1.1 in obese as compared to nonobese patients (CI, 0.9-1.6) whereas among patients without diabetes, the RR was 1.0 (CI, 0.7-1.5). Which of the following is the best interpretation of this study’s findings?
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Question 40 of 40
40. Question
A 32-year-old woman comes to the physician with urinary burning and frequency. She has no fever or back pain. Midstream urine (MSU) cultures grow 105 colony forming units (CFU)/mL of enterococci. A previous publication studied the accuracy of MSU culture in identifying the causative pathogen in patients with uncomplicated cystitis. Women ages 18–49 with symptoms of cystitis provided MSU specimens for culture. The investigators also collected urine by means of a urethral catheter for culture, which served as the gold standard for confirming the causative pathogen. The following results relating to enterococcal growth were reported for 404 specimens:
Enterococci (CFU/mL)
Sensitivity
Specificity
>102
4/4 (100%)
363/400 (91%)
>103
4/4 (100%)
374/400 (94%)
>104
4/4 (100%)
393/400 (98%)
>105
2/4 (50%)
394/400 (98%)
Based on the study results, what is the positive predictive value of enterococcal growth of 105 CFU/mL in the MSU sample?
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