A cohort study was performed to determine the relationship between elevated LDL levels and the development of a myocardial infarction. After a 7-year follow up trial period, the following data was analyzed (Table below).
Which of the following is the 7-year risk of getting a myocardial infarction in patients with elevated LDL levels?
0.6 (60%). Risk is essentially a measure of the incidence of the disease. Note that in this question we are looking for risk as opposed to relative risk. Risk is calculated by dividing the number of patients with the disease (myocardial infarction) by the overall number of patients at risk (so 60 divided by 100). (A) 0.2 (20%) is the risk of getting a myocardial infarction in patients without elevated LDL levels. (B) 0.3 (30%) is the relative risk of getting a myocardial infarction in those patients with elevated LDL levels (here we divide the risks in each groups by each other, so 0.6 divided by 0.2). (C) 0.4 (40%) is the 7-year risk of getting a myocardial infarction in all patients in this study (80 divided by 200). Absolute risk reduction (ARR) is essentially the risk difference and here would be the difference between the two groups’ risks (0.6 − 0.2 = 0.4). ARR is the inverse of number needed to treat (NNT), so to find NNT, we divide 1 by 0.4 and round up. 1 divided by 0.4 is 2.5, so NNT is 3.
A 62-year-old man presents with a 3-month history of weakness, fatigue, and weight loss. He also reports a burning epigastric pain. The patient has an insignificant past medical history and smokes 2 packs of cigarettes per day. He drinks 4 to 5 beers per day as well. Work-up is initiated and the patient is found to have a positive fecal occult blood test. Esophagogastroduodenoscopy is performed and demonstrates a fundal ulcer. Biopsy is performed and is positive for adenocarcinoma.
Which of the following is the best next step in management of this patient?
CT scan. When a malignancy is diagnosed histologically, it is critical to determine the extent of the malignancy to aid in timely and correct patient care. In patients with newly diagnosed gastric cancer, CT scan is the modality of choice to evaluate for the extent of the disease. The stage will allow the physician to determine the most appropriate therapy. CT is employed due to its high sensitivity in determining metastases (particularly liver metastases). (A) H. pylori is strongly associated with gastric lymphoma, not in adenocarcinoma. (C) Laparoscopy could be used after CT scan is performed to detect metastases not noticed on the CT scan. (D) It is too early to determine the need for hospice care and prognosis without accurately staging the disease.
A 22-year-old man presents with headache, vomiting, and confusion. His girlfriend reports that he was at a local bar that was hosting a barbeque. Due to inclement weather, the barbecue was held indoors. Physical examination reveals a heart rate of 112 beats per minute, respiratory rate of 24 breaths per minute, and diffusely pink skin.
Which of the following is the most likely diagnosis in this patient?
Carbon monoxide poisoning. This patient is presenting a history highly consistent with carbon monoxide poisoning (smoke inhalation from several sources such as automobiles, furnaces, and even charcoal grills). Carbon monoxide prevents organs and tissues from using oxygen effectively. Acute symptoms include headaches, vomiting, abdominal pain, confusion, and sometimes coma. Dermatologic findings include a pinkish-red skin hue. Diagnosis is confirmed by ordering carboxyhemoglobin levels and treatment is with supplemental oxygen. Another very important clue to the diagnosis of carbon monoxide poisoning includes several people presenting at the same time with similar symptoms who were in the same confined quarters.
(A) Cyanide poisoning occurs from burning of rubber or plastic and is associated with a stereotypical “bitter almond breath.” Given that the symptoms are highly similar to carbon monoxide poisoning, clinical history is crucial! (C) Methemoglobinemia can occur from drugs and environmental exposures, and unlike carbon monoxide and cyanide, it is characterized by a cyanosis and bluish discoloration of the skin.
A 29-year-old woman is brought to the Emergency Department after falling from the balcony located on the third story of her apartment building. She reports severe abdominal pain and distention is noted on physical examination. Urgent laparotomy confirms a splenic laceration and a splenectomy is performed. The patient does well postoperatively.
Which of the following vaccines is recommended in this patient?
Meningococcal. This patient has undergone a splenectomy and is now at significant risk for infection caused by the encapsulated organisms. The mnemonic “SHiNKS” can help one recall several of these organisms: S. pneumoniae, H. influenzae, N. meningitidis, Klebsiella, and Salmonella. Without the spleen, phagocytes are unable to recognize and “engulf ” these organisms, so patients who have received a splenectomy must receive several vaccinations. The ones that are commonly given are vaccinations against S. pneumoniae, H. influenzae, and N. meningitidis. (A, B) These vaccines should be given in different contexts (Hepatitis A for travel to endemic areas and patients with chronic liver disease; Pertussis is in the standard childhood vaccination series). Neither of these organisms pose risk specifically for an asplenic patient. (C) Although Salmonella typhi is encapsulated, vaccination is only necessary for travelers to endemic countries (no current recommendation for postsplenectomy patients).
Several academic dermatologists are conducting a study to determine the risk factors for acral lentiginous melanoma versus superficial spreading melanoma. A hundred and twenty patients are identified with a diagnosis of acral lentiginous melanoma and 140 patients are identified with a diagnosis of superficial spreading melanoma. The researchers subsequently engage in a thorough review of the patients’ medical records, demographic characteristics, and family history. They then execute a side-by-side comparison of the differences ascertained between the two groups.
Which of the following is the study design being implemented in this example?
Case-control study. In this study design, the researchers first determined the outcome (acral lentiginous or superficial spreading melanoma). Following identification of the outcome, it is only then that they looked for associated risk factors. This is the definition of a case-control study. (A) Retrospective cohort study is very similar to case-control, but the order in which outcomes and risk factors are determined is opposite. In a retrospective cohort study, risk factor exposure is determined first and then the outcome of interest is determined later. (C) Prospective cohort study is looking ahead, not looking back. Subjects with exposure and those without exposure are followed over time to determine the outcome of interest. (D) Cross-sectional studies assess both exposure (risk factors) and outcome at a single point in time. It is used to determine prevalence. Table below summarizes the different study types.
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