You find that the specific disease that you are studying is very rare in your patient population. You are interested in determining which risk factors may contribute to the development of this disease.
Which study design would be the most appropriate to further pursue this question?
A. case-control study
B. cohort study
C. prospective, randomized-controlled trial
D. cross-sectional study
E. meta-analysis
Correct Answer: A Section: (none)
Explanation: Explanations: All types of study designs have potential benefits and drawbacks and it is important to understand this when designing research or reviewing research reports. A cross-sectional study is one in which information is gathered from a certain population at one point in time with no follow-up period. This type of study is very useful for the determination of the prevalence of a disease or risk factor in a population at a certain point in time. Cross-sectional studies cannot determine cause and effect because there are no interventions being made and there is no follow-up. A case-control study is very useful and efficient at studying diseases that occur rarely. In a case-control study, persons with a disease are identified and then information is determined by looking back in time (i.e., retrospective review). Apopulation of those without the disease (controls) is also defined and studied in the same way.
The prevalence of a risk factor in the cases and controls can then be determined and compared. A case-control study cannot prove cause and effect, but it can be a powerful tool to determine risk factors that can generate hypotheses for further study. Acohort study is one in which a population is defined and then followed over time. A cohort study may be either prospective or etrospective. Cohort studies can be used to describe the incidence of diseases over time or to determine associations between predictors and outcomes. Cohort studies are inefficient for the study of rare outcomes, as a very large sample size would be required in order to find a few events. Aprospective, randomizedcontrolled trial is the gold standard study for determining the effect of a treatment or intervention. It is not the type of study that would be used to determine the prevalence of a disease in a population or to determine what risk factors are associated with the development of a disease. A meta-analysis is a systematic review of completed research studies. By evaluating similarly done studies, the meta-analysis technique can allow for an evaluation of a body of literature and can be used to increase the overall statistical power by creating a larger sample by combining studies.
The odds ratios given in question 44 show that both risk factors X and Y occurred more often in those with the disease (cases) than they did in those without the disease (controls). Neither of the CIs given cross 1, therefore, these are statistically significant findings. We cannot use this type of study to definitively prove cause and effect, therefore option A is false. While risk factor X had a higher odds ratio for the development of the disease than risk factor Y, no prognostic data are supplied and none can be inferred from the information given, therefore B is false. The odds ratios as given in this case compare the prevalence of a risk factor in the case group with the control group, not the prevalence of one risk factor compared to another. For this reason, we cannot say which risk factor is more common in the population and option C is false. No absolute numbers are presented in this question and therefore we cannot determine how often each of the risk factors occurs in our population, so E is false as well
Question 152:
You would like to design a study to evaluate the prevalence of a certain disease in your patient population. Which study design would be the most appropriate?
A. case-control study
B. cohort study
C. prospective, randomized-controlled trial
D. cross-sectional study
E. meta-analysis
Correct Answer: D Section: (none)
Explanation: Explanations: All types of study designs have potential benefits and drawbacks and it is important to understand this when designing research or reviewing research reports. A cross-sectional study is one in which information is gathered from a certain population at one point in time with no follow-up period. This type of study is very useful for the determination of the prevalence of a disease or risk factor in a population at a certain point in time. Cross-sectional studies cannot determine cause and effect because there are no interventions being made and there is no follow-up. A case-control study is very useful and efficient at studying diseases that occur rarely. In a case-control study, persons with a disease are identified and then information is determined by looking back in time (i.e., retrospective review). Apopulation of those without the disease (controls) is also defined and studied in the same way.
The prevalence of a risk factor in the cases and controls can then be determined and compared. A case-control study cannot prove cause and effect, but it can be a powerful tool to determine risk factors that can generate hypotheses for further study. Acohort study is one in which a population is defined and then followed over time. A cohort study may be either prospective or etrospective. Cohort studies can be used to describe the incidence of diseases over time or to determine associations between predictors and outcomes. Cohort studies are inefficient for the study of rare outcomes, as a very large sample size would be required in order to find a few events. Aprospective, randomizedcontrolled trial is the gold standard study for determining the effect of a treatment or intervention. It is not the type of study that would be used to determine the prevalence of a disease in a population or to determine what risk factors are associated with the development of a disease. A meta-analysis is a systematic review of completed research studies. By evaluating similarly done studies, the meta-analysis technique can allow for an evaluation of a body of literature and can be used to increase the overall statistical power by creating a larger sample by combining studies.
The odds ratios given in question 44 show that both risk factors X and Y occurred more often in those with the disease (cases) than they did in those without the disease (controls). Neither of the CIs given cross 1, therefore, these are statistically significant findings. We cannot use this type of study to definitively prove cause and effect, therefore option A is false. While risk factor X had a higher odds ratio for the development of the disease than risk factor Y, no prognostic data are supplied and none can be inferred from the information given, therefore B is false. The odds ratios as given in this case compare the prevalence of a risk factor in the case group with the control group, not the prevalence of one risk factor compared to another. For this reason, we cannot say which risk factor is more common in the population and option C is false. No absolute numbers are presented in this question and therefore we cannot determine how often each of the risk factors occurs in our population, so E is false as well
Question 153:
A 34-year-old woman with a history of type 1 diabetes mellitus presents to your office for a routine follow-up visit. She is feeling well and has no complaints. Her fasting blood sugars usually run 140 160 and her HgbA1C was recently measured at 8.2. She tells you that she would like to become pregnant but wants to know if there are any risks for her and a baby due to her diabetes.
Which of the following preconception counseling statements is true?
A. All diabetics planning to become pregnant should be placed on ACE inhibitors for renal protection.
B. Diabetic women should not take folic acid because all commercially available supplements contain sugar.
C. The goal HgbA1C level during her pregnancy is approximately 9%.
D. Insulin pump treatment is contraindicated during pregnancy.
E. Women with good preconception diabetic control have infants with a lower incidence of congenital malformations than women with poor preconception diabetic control.
Correct Answer: E Section: (none)
Explanation: Explanations: Pregestational diabetes is associated with numerous risks to both the mother and the fetus. Stillbirths are more common in pregnancies to diabetic women and stillbirths without an identifiable cause, called "unexplained" stillbirths, are a well-described phenomenon. Similarly, preterm births are more common in diabetics than nondiabetics. While congenital malformations are more common in pregnancies to diabetic women, fetal chromosomal abnormalities are not more common. Children of women with diabetes have an approximately 13% incidence of developing type 1 diabetes. While earlier obstetrical teaching suggested that maternal diabetes delayed fetal lung maturation, more recent studies do not support this. Gestational age is likely the most significant factor in the development of respiratory distress. While there are significant maternal risks from the interaction of diabetes and pregnancy, with the possible exception of diabetic retinopathy, the long-term course of diabetes does not appear to be affected by pregnancy.
Pregnancy neither exacerbates nor modifies diabetic nephropathy and the development of diabetic peripheral neuropathy during pregnancy is uncommon. While preeclampsia is a significant risk and the perinatal mortality rate is 20 times higher in preeclamptic diabetic women compared to normotensive women, the occurrence of preeclampsia does not appear to be related to diabetic control. Diabetic ketoacidosis is a serious complication with an approximately 20% rate of fetal loss. However, it is estimated to occur in 1% of pregnancies of diabetic women. Infections occur in approximately 80% of pregnancies in insulin-dependent diabetics, with candida vaginitis, urinary tract infections, and respiratory infections being common. Preconception counseling in diabetic women who desire to become pregnant is a critical issue that often is best served by a team that includes the obstetrician, primary care physician, endocrinologist, and diabetic educators. When possible, attempts should be made to attain optimal diabetic control. Women with good diabetic control have been shown in observational studies to have a lower rate of having infants with congenital anomalies than women with poorer diabetic control. Optimal diabetic control has been defined as glycated hemoglobin levels within or near the upper limit of the normal range. This can be obtained with multiple daily insulin injections or, in selected patients, a continuous infusion via an insulin pump. All women--diabetic or not should be counseled to take folic acid prior to conception in order to lower the rate of neural tube defects. ACE inhibitors are contraindicated during pregnancy and should, whenever possible, be discontinued prior to conception.
Question 154:
A 34-year-old woman with a history of type 1 diabetes mellitus presents to your office for a routine follow-up visit. She is feeling well and has no complaints. Her fasting blood sugars usually run 140 160 and her HgbA1C was recently measured at 8.2. She tells you that she would like to become pregnant but wants to know if there are any risks for her and a baby due to her diabetes.
Which of the following statements regarding the risk of pregnancy to the diabetic mother is true?
A. Pregnancy significantly exacerbates diabetic nephropathy.
B. Most diabetic women will develop neuropathic symptoms while pregnant.
C. About 10% of diabetic women will develop ketoacidosis during pregnancy.
D. Most diabetic women develop at least one infection during pregnancy.
E. The occurrence of preeclampsia is directly related to diabetic control
Correct Answer: D Section: (none)
Explanation: Explanations: Pregestational diabetes is associated with numerous risks to both the mother and the fetus. Stillbirths are more common in pregnancies to diabetic women and stillbirths without an identifiable cause, called "unexplained" stillbirths, are a well-described phenomenon. Similarly, preterm births are more common in diabetics than nondiabetics. While congenital malformations are more common in pregnancies to diabetic women, fetal chromosomal abnormalities are not more common. Children of women with diabetes have an approximately 13% incidence of developing type 1 diabetes. While earlier obstetrical teaching suggested that maternal diabetes delayed fetal lung maturation, more recent studies do not support this. Gestational age is likely the most significant factor in the development of respiratory distress. While there are significant maternal risks from the interaction of diabetes and pregnancy, with the possible exception of diabetic retinopathy, the long-term course of diabetes does not appear to be affected by pregnancy. Pregnancy neither exacerbates nor modifies diabetic nephropathy and the development of diabetic peripheral neuropathy during pregnancy is uncommon. While preeclampsia is a significant risk and the perinatal mortality rate is 20 times higher in preeclamptic diabetic women compared to normotensive women, the occurrence of preeclampsia does not appear to be related to diabetic control. Diabetic ketoacidosis is a serious complication with an approximately 20% rate of fetal loss. However, it is estimated to occur in 1% of pregnancies of diabetic women. Infections occur in approximately 80% of pregnancies in insulin-dependent diabetics, with candida vaginitis, urinary tract infections, and respiratory infections being common. Preconception counseling in diabetic women who desire to become pregnant is a critical issue that often is best served by a team that includes the obstetrician, primary care physician, endocrinologist, and diabetic educators. When possible, attempts should be made to attain optimal diabetic control. Women with good diabetic control have been shown in observational studies to have a lower rate of having infants with congenital anomalies than women with poorer diabetic control. Optimal diabetic control has been defined as glycated hemoglobin levels within or near the upper limit of the normal range. This can be obtained with multiple daily insulin injections or, in selected patients, a continuous infusion via an insulin pump. All women--diabetic or not should be counseled to take folic acid prior to conception in order to lower the rate of neural tube defects. ACE inhibitors are contraindicated during pregnancy and should, whenever possible, be discontinued prior to conception.
Question 155:
A 34-year-old woman with a history of type 1 diabetes mellitus presents to your office for a routine follow-up visit. She is feeling well and has no complaints. Her fasting blood sugars usually run 140 160 and her HgbA1C was recently measured at 8.2. She tells you that she would like to become pregnant but wants to know if there are any risks for her and a baby due to her diabetes.
Which of the following statements about the risk to offspring of diabetic mothers is true?
A. Approximately 20% of children of diabetic mothers will develop type 1 diabetes.
B. Diabetes is associated with an increased risk of stillbirth.
C. Diabetes is associated with an increased risk of chromosomal anomalies.
D. The incidence of preterm birth is the same in both diabetics and nondiabetics.
E. Maternal diabetes delays the development of fetal lung maturity.
Correct Answer: B Section: (none)
Explanation: Explanations: Pregestational diabetes is associated with numerous risks to both the mother and the fetus. Stillbirths are more common in pregnancies to diabetic women and stillbirths without an identifiable cause, called "unexplained" stillbirths, are a well-described phenomenon. Similarly, preterm births are more common in diabetics than nondiabetics. While congenital malformations are more common in pregnancies to diabetic women, fetal chromosomal abnormalities are not more common. Children of women with diabetes have an approximately 13% incidence of developing type 1 diabetes. While earlier obstetrical teaching suggested that maternal diabetes delayed fetal lung maturation, more recent studies do not support this. Gestational age is likely the most significant factor in the development of respiratory distress. While there are significant maternal risks from the interaction of diabetes and pregnancy, with the possible exception of diabetic retinopathy, the long-term course of diabetes does not appear to be affected by pregnancy.
Pregnancy neither exacerbates nor modifies diabetic nephropathy and the development of diabetic peripheral neuropathy during pregnancy is uncommon. While preeclampsia is a significant risk and the perinatal mortality rate is 20 times higher in preeclamptic diabetic women compared to normotensive women, the occurrence of preeclampsia does not appear to be related to diabetic control. Diabetic ketoacidosis is a serious complication with an approximately 20% rate of fetal loss. However, it is estimated to occur in 1% of pregnancies of diabetic women. Infections occur in approximately 80% of pregnancies in insulin-dependent diabetics, with candida vaginitis, urinary tract infections, and respiratory infections being common. Preconception counseling in diabetic women who desire to become pregnant is a critical issue that often is best served by a team that includes the obstetrician, primary care physician, endocrinologist, and diabetic educators. When possible, attempts should be made to attain optimal diabetic control. Women with good diabetic control have been shown in observational studies to have a lower rate of having infants with congenital anomalies than women with poorer diabetic control. Optimal diabetic control has been defined as glycated hemoglobin levels within or near the upper limit of the normal range. This can be obtained with multiple daily insulin injections or, in selected patients, a continuous infusion via an insulin pump. All women--diabetic or not should be counseled to take folic acid prior to conception in order to lower the rate of neural tube defects. ACE inhibitors are contraindicated during pregnancy and should, whenever possible, be discontinued prior to conception.
Question 156:
A 65-year-old White woman presents to your office and requests to have a screening test for osteoporosis.
She has been menopausal for 15 years. She never took hormone replacement therapy (HRT). She currently takes 500 mg of calcium a day and walks 2 miles a day. She has no history of fractures.
The result of the test that you ordered shows the patient's bone mineral density to be 2.5 standard deviations below the mean bone density of a 25-year-old woman. What is the most appropriate management at this point?
A. start therapy with an oral bisphosphonate
B. increase her calcium supplement to 1000 mg/day
C. suggest diet and exercise changes then recheck her bone density in 6 months
D. add vitamin D and continue her current calcium supplement
E. no intervention as her bone density is considered normal for her age
Correct Answer: A Section: (none)
Explanation: Explanations: DEXA is the most widely used test for the screening and diagnosis of osteoporosis. It is sensitive for the loss of bone density, exposes the patient to a relatively low dose of radiation, and is widely available at a reasonable cost. It is the mode of evaluation that has been used in most of the studies of the evaluation and management of osteoporosis. The American College of Radiology Guidelines state that DEXA of the lumbar spine and proximal femur is the most appropriate screening test for osteoporosis in postmenopausal women who are not on any therapy. Quantitative CT scanning is also highly sensitive but is less widely available, more expensive, and exposes the subject to higher radiation doses. Lateral thoracic spine radiographs can diagnose or confirm the presence of osteoporotic fractures but are not appropriate as a screening test for bone density. Quantitative ultrasonography, usually of the calcaneus or digits, is becoming more widely available at low costs, but has the disadvantage of being unable to directly evaluate the areas where most ostoporotic fractures are likely to occur--hip, spine, and radius. SXA has not correlated as well to fracture risk as dual energy techniques and is, therefore, less appropriate than DEXA.
Question 157:
A 65-year-old White woman presents to your office and requests to have a screening test for osteoporosis. She has been menopausal for 15 years. She never took hormone replacement therapy (HRT). She currently takes 500 mg of calcium a day and walks 2 miles a day. She has no history of fractures.
Which of the following tests would be the most appropriate screening test to perform?
A. lateral thoracic spine x-ray
B. dual energy x-ray absorptiometry (DEXA) of the lumbar spine and proximal femur
C. quantitative ultrasound of the phalanges of the hand
D. peripheral quantitative computed tomography (CT) of the distal radius
E. single energy x-ray absorptiometry (SXA) of the calcaneus
Correct Answer: B Section: (none)
Explanation: Explanations: DEXA is the most widely used test for the screening and diagnosis of osteoporosis. It is sensitive for the loss of bone density, exposes the patient to a relatively low dose of radiation, and is widely available at a reasonable cost. It is the mode of evaluation that has been used in most of the studies of the evaluation and management of osteoporosis. The American College of Radiology Guidelines state that DEXA of the lumbar spine and proximal femur is the most appropriate screening test for osteoporosis in postmenopausal women who are not on any therapy. Quantitative CT scanning is also highly sensitive but is less widely available, more expensive, and exposes the subject to higher radiation doses. Lateral thoracic spine radiographs can diagnose or confirm the presence of osteoporotic fractures but are not appropriate as a screening test for bone density. Quantitative ultrasonography, usually of the calcaneus or digits, is becoming more widely available at low costs, but has the disadvantage of being unable to directly evaluate the areas where most ostoporotic fractures are likely to occur--hip, spine, and radius. SXA has not correlated as well to fracture risk as dual energy techniques and is, therefore, less appropriate than DEXA.
Question 158:
A 50-year-old male presents to your office after reading an article on the Internet stating that a recent study showed that the drug finasteride can prevent prostate cancer. He asks you to prescribe this medication for him. You review the article and find the following information: a randomizedcontrolled trial of men over the age of 55 with normal prostate-specific antigen (PSA) readings was performed comparing finasteride and a placebo. At the end of the study, 18% of the men in the finasteride group and 24% of the men in the placebo group had developed prostate cancer.
Further review of the article reveals that 6.4% of the men in the finasteride group and 5.1% in the placebo group developed high-grade prostate cancers. How many men need to take finasteride in order to have one excess case of high-grade prostate cancer (number needed to harm [NNH])?
A. 1.3
B. 12
C. 37
D. 77
E. 94
Correct Answer: D Section: (none)
Explanation: Explanations: The NNT is calculated by first determining the ARR for a specific outcome between two groups in a study. The ARR, or risk difference, is calculated by subtracting the percentage of subjects who develop an outcome in the treatment group from the percentage who develop the outcome in the control group. In question 35, the outcome considered is the development of prostate cancer. This occurred in 24% of the control group and 18% of the finasteride group. The ARR is calculated as 24% -18% = 6% or
0.06. The NNT is calculated as: NNT = 1/ARR. In this example, the NNT = 1/0.06 = 16.67, approximately 17. This suggests that for every 17 men who took finasteride there was one fewer case of prostate cancer. The NNH is calculated in exactly the same manner as the NNT. The only difference is that the outcome is adverse. In this study, highgrade prostate cancers occurred more often in the finasteride group than the placebo group; 6.4% of men who took finasteride and 5.1% who took a placebo developed high-grade prostate cancer. The risk difference, in this case an absolute risk increase, is 6.4% -5.1% = 1.3% or 0.013. The NNH = 1/absolute risk increase = 1/0.013 = 77
Question 159:
A 50-year-old male presents to your office after reading an article on the Internet stating that a recent study showed that the drug finasteride can prevent prostate cancer. He asks you to prescribe this medication for him. You review the article and find the following information: a randomizedcontrolled trial of men over the age of 55 with normal prostate-specific antigen (PSA) readings was performed comparing finasteride and a placebo. At the end of the study, 18% of the men in the finasteride group and 24% of the men in the placebo group had developed prostate cancer.
How many men need to be treated with finasteride to prevent one case of prostate cancer (NNT)?
A. 6
B. 10
C. 17
D. 24
E. 32
Correct Answer: C Section: (none)
Explanation: Explanations: The NNT is calculated by first determining the ARR for a specific outcome between two groups in a study. The ARR, or risk difference, is calculated by subtracting the percentage of subjects who develop an outcome in the treatment group from the percentage who develop the outcome in the control group. In question 35, the outcome considered is the development of prostate cancer. This occurred in 24% of the control group and 18% of the finasteride group. The ARR is calculated as 24% -18% = 6% or
0.06. The NNT is calculated as: NNT = 1/ARR. In this example, the NNT = 1/0.06 = 16.67, approximately 17. This suggests that for every 17 men who took finasteride there was one fewer case of prostate cancer. The NNH is calculated in exactly the same manner as the NNT. The only difference is that the outcome is adverse. In this study, highgrade prostate cancers occurred more often in the finasteride group than the placebo group; 6.4% of men who took finasteride and 5.1% who took a placebo developed high-grade prostate cancer. The risk difference, in this case an absolute risk increase, is 6.4% -5.1% = 1.3% or 0.013. The NNH = 1/absolute risk increase = 1/0.013 = 77
Question 160:
Which of the following statements regarding vaccinations of pregnant women is true?
A. Women who will be beyond the first trimester of pregnancy during flu season should routinely receive the inactivated influenza vaccine.
B. Pregnancy is an absolute contraindication to the hepatitis B vaccine.
C. Women who test negative for rubella at their initial prenatal visit should routinely receive a rubella vaccine during their second trimester of pregnancy.
D. Pregnant women who have not completed a Td primary series should start this series in the immediate postpartum period.
E. Women who receive a rubella vaccination within 4 weeks of becoming pregnant should be advised of the high risk having a baby with congenital rubella syndrome.
Correct Answer: A Section: (none)
Explanation: Explanations: There is an increased risk of influenzarelated complications in pregnant women who contract influenza, therefore the influenza vaccine is recommended for all pregnant women who will be beyond the first trimester during influenza season. The live, attenuated influenza vaccine is contraindicated during pregnancy but the inactivated influenza vaccine is recommended. The hepatitis B vaccine contains only noninfectious hepatitis B surface antigen particles and poses no real or theoretical risk of fetal infection, whereas the disease hepatitis B may cause severe illness for the pregnant woman and chronic disease for the newborn. For these reasons, neither pregnancy nor lactation is a contraindication to vaccination with hepatitis B vaccine. All pregnant women should routinely be tested for immunity to the rubella virus and should be immunized postpartum if they have no measurable immunity. The rubella vaccine, like other livevirus vaccines, is contraindicated during pregnancy due to the theoretical risk of causing fetal infection. In reality, studies of women who were pregnant or soon became pregnant after receiving rubella vaccination showed that the risk is extremely small. Aregistry of 226 usceptible women who received the rubella vaccine between 3 months before and 3 months after conception showed no evidence of congenital rubella syndrome. Women who inadvertently receive this vaccine should be counseled about the theoretical risk involved, however this would not be considered a reason to terminate a pregnancy. Finally, Td toxoid is routinely indicated for pregnant women.
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