Screening interval determination US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Screening interval determination. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Screening interval determination US Medical PG Question 1: A 68-year-old man presents to the office for his annual physical examination. He has no current complaints. Past medical history is unremarkable. He reports a 30-pack-year smoking history but no alcohol or drug use. Review of systems is only remarkable for thicker mucous production that is worse in the morning when he coughs. A non-contrast CT scan of his chest is performed, and the doctor informs him that a 2 cm nodule has been identified in his upper lobe of the left lung near the left main bronchus and that further testing is required to rule out malignancy. The patient is surprised by this news since he has never experienced any alarming symptoms. The doctor informs him that lung cancers don’t usually present with symptoms until late in the course of the disease. The doctor says that sometimes it may take several years before it becomes severe enough to cause symptoms, which is why patients with risk factors for developing lung cancer are screened at an earlier age than the general public. Which of the following concepts is being described by the doctor to this patient?
- A. Confounding bias
- B. Latent period (Correct Answer)
- C. Induction period
- D. Lead time bias
- E. Surveillance bias
Screening interval determination Explanation: ***Latent period***
- This refers to the interval between the **disease onset** (biological initiation) and the appearance of **detectable symptoms**.
- In lung cancer, this period can be long, explaining why a large nodule is found in an asymptomatic patient.
*Confounding bias*
- This occurs when an **unaccounted-for variable** (the confounder) influences both the exposure and the outcome, distorting their true relationship.
- It relates to study design and interpretation, not the natural history of a disease.
*Induction period*
- This is the time from **causal exposure** (e.g., smoking) to the initiation of the disease, which is the **biological onset**.
- While smoking is a cause of lung cancer, the doctor is describing the time from the disease's silent progression to symptom manifestation.
*Lead time bias*
- This bias occurs in screening programs when **early detection** (by screening) makes it seem like patients live longer, even if their actual survival time from disease onset hasn't changed.
- The doctor is explaining why the patient is asymptomatic despite a large nodule, not a bias related to screening effectiveness.
*Surveillance bias*
- Occurs when a **higher rate of diagnosis** is observed in one group due to more frequent or intense monitoring, leading to an apparent increase in disease incidence.
- This is a form of information bias in epidemiological studies, not a description of disease progression.
Screening interval determination US Medical PG Question 2: A student health coordinator plans on leading a campus-wide HIV screening program that will be free for the entire undergraduate student body. The goal is to capture as many correct HIV diagnoses as possible with the fewest false positives. The coordinator consults with the hospital to see which tests are available to use for this program. Test A has a sensitivity of 0.92 and a specificity of 0.99. Test B has a sensitivity of 0.95 and a specificity of 0.96. Test C has a sensitivity of 0.98 and a specificity of 0.93. Which of the following testing schemes should the coordinator pursue?
- A. Test A on the entire student body followed by Test B on those who are positive
- B. Test A on the entire student body followed by Test C on those who are positive
- C. Test C on the entire student body followed by Test B on those who are positive
- D. Test C on the entire student body followed by Test A on those who are positive (Correct Answer)
- E. Test B on the entire student body followed by Test A on those who are positive
Screening interval determination Explanation: ***Test C on the entire student body followed by Test A on those who are positive***
- To "capture as many correct HIV diagnoses as possible" (maximize true positives), the initial screening test should have the **highest sensitivity**. Test C has the highest sensitivity (0.98).
- To "capture as few false positives as possible" (maximize true negatives and confirm diagnoses), the confirmatory test should have the **highest specificity**. Test A has the highest specificity (0.99).
*Test A on the entire student body followed by Test B on those who are positive*
- Starting with Test A (sensitivity 0.92) would miss more true positive cases than starting with Test C (sensitivity 0.98), failing the goal of **capturing as many cases as possible**.
- Following with Test B (specificity 0.96) would result in more false positives than following with Test A (specificity 0.99).
*Test A on the entire student body followed by Test C on those who are positive*
- This scheme would miss many true positive cases initially due to Test A's lower sensitivity compared to Test C.
- Following with Test C would introduce more false positives than necessary, as it has a lower specificity (0.93) than Test A (0.99).
*Test C on the entire student body followed by Test B on those who are positive*
- While Test C is a good initial screen for its high sensitivity, following it with Test B (specificity 0.96) is less optimal than Test A (specificity 0.99) for minimizing false positives in the confirmation step.
- This combination would therefore yield more false positives in the confirmatory stage than using Test A.
*Test B on the entire student body followed by Test A on those who are positive*
- Test B has a sensitivity of 0.95, which is lower than Test C's sensitivity of 0.98, meaning it would miss more true positive cases at the initial screening stage.
- While Test A provides excellent specificity for confirmation, the initial screening step is suboptimal for the goal of capturing as many diagnoses as possible.
Screening interval determination US Medical PG Question 3: 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. 330 / (330 + 30)
- B. 330 / (330 + 70) (Correct Answer)
- C. 370 / (30 + 370)
- D. 370 / (70 + 370)
- E. 330 / (400 + 400)
Screening interval determination Explanation: ***330 / (330 + 70)***
- **Sensitivity** measures the proportion of actual **positives** that are correctly identified as such.
- In this study, there are **400 diseased patients** (half of 800). Of these, 330 tested positive (true positives), meaning 70 tested negative (false negatives). So sensitivity is **330 / (330 + 70)**.
*330 / (330 + 30)*
- This calculation represents the **positive predictive value**, which is the probability that subjects with a positive screening test truly have the disease. It uses **true positives / (true positives + false positives)**.
- It does not correctly calculate **sensitivity**, which requires knowing the total number of diseased individuals.
*370 / (30 + 370)*
- This expression is attempting to calculate **specificity**, which is the proportion of actual negatives that are correctly identified. It would be **true negatives / (true negatives + false positives)**.
- However, the numbers used are incorrect for specificity in this context given the data provided.
*370 / (70 + 370)*
- This formula is an incorrect combination of values and does not represent any standard epidemiological measure like **sensitivity** or **specificity**.
- It is attempting to combine false negatives (70) and true negatives (370 from control arm) in a non-standard way.
*330 / (400 + 400)*
- This calculation attempts to divide true positives by the total study population (800 patients).
- This metric represents the **prevalence of true positives within the entire study cohort**, not the test's **sensitivity**.
Screening interval determination US Medical PG Question 4: A 65-year-old non-smoking woman with no symptoms comes to your clinic to establish care with a primary care provider. She hasn’t seen a doctor in 12 years and states that she feels very healthy. You realize that guidelines by the national cancer organization suggest that she is due for some cancer screening tests, including a mammogram for breast cancer, a colonoscopy for colon cancer, and a pap smear for cervical cancer. These three screening tests are most likely to be considered which of the following?
- A. Tertiary prevention
- B. Primary prevention
- C. Secondary prevention (Correct Answer)
- D. Cancer screening does not fit into these categories
- E. Quaternary prevention
Screening interval determination Explanation: ***Secondary prevention***
- **Secondary prevention** aims to detect and treat a disease early, before symptoms appear, to prevent its progression or recurrence.
- **Cancer screening tests** such as mammograms, colonoscopies, and Pap smears fit this category perfectly as they are performed in asymptomatic individuals to identify early-stage cancer or pre-cancerous lesions.
*Tertiary prevention*
- **Tertiary prevention** focuses on minimizing the impact of an established disease and improving quality of life through treatment and rehabilitation.
- This would involve managing existing cancer, not screening for it.
*Primary prevention*
- **Primary prevention** aims to prevent a disease from occurring in the first place, often through health promotion and risk reduction.
- Examples include vaccination, lifestyle modifications (e.g., healthy diet, exercise), or avoiding smoking.
*Cancer screening does not fit into these categories*
- This statement is incorrect as cancer screening is a well-established component of preventive healthcare.
- It clearly falls within the defined categories of prevention, specifically secondary prevention.
*Quaternary prevention*
- **Quaternary prevention** aims to protect patients from medical interventions that are likely to cause more harm than good, or to avoid over-medicalization.
- This concept is distinct from screening for diseases and focuses on ethical considerations in medical care.
Screening interval determination US Medical PG Question 5: A 21-year-old U.S. born first year medical student with no prior hospital or healthcare work presents to the physician for a routine physical exam. The patient is HIV negative, denies drug use, and denies sick contacts. The physician places a purified protein tuberculin test in the patient's right forearm intradermally. What is the proper time to read the test and induration diameter that would indicate a positive test result?
- A. 36 hours and 7mm diameter
- B. 48 hours and 11mm diameter
- C. 72 hours and 16mm diameter (Correct Answer)
- D. 96 hours and 14mm diameter
- E. 24 hours and 18mm diameter
Screening interval determination Explanation: ***72 hours and 16mm diameter***
- The **purified protein derivative (PPD) test** should ideally be read between 48 and 72 hours after administration to allow for the **Type IV hypersensitivity reaction** to fully develop.
- For individuals with no known risk factors for tuberculosis and no prior exposure, an induration of **≥15 mm** is considered a positive result. A 16mm diameter falls within this range.
*36 hours and 7mm diameter*
- **36 hours** is too early to accurately read a PPD test, as the delayed-type hypersensitivity reaction may not have fully manifested.
- A **7mm induration** would generally be considered negative in a low-risk individual, as the threshold for positivity in this group is higher.
*48 hours and 11mm diameter*
- While **48 hours** is within the acceptable window for reading a PPD test, an **11mm induration** is not considered positive for a young, low-risk individual without any predisposing conditions like HIV or organ transplant.
- The threshold for a positive result in this demographic is typically **≥15 mm**.
*96 hours and 14mm diameter*
- **96 hours** (4 days) is generally too late to accurately read a PPD test, as the reaction may begin to fade, leading to a potentially false negative.
- A **14mm induration** is still below the positive threshold of ≥15mm for a low-risk individual.
*24 hours and 18mm diameter*
- **24 hours** is significantly too early to read a PPD test, as the immune response will not have fully developed, leading to unreliable results.
- While **18mm induration** would be a positive result, the timing makes the reading invalid.
Screening interval determination US Medical PG Question 6: A 50-year-old Caucasian man presents for a routine checkup. He does not have any current complaint. He is healthy and takes no medications. He has smoked 10–15 cigarettes per day for the past 10 years. His family history is negative for gastrointestinal disorders. Which of the following screening tests is recommended for this patient according to the United States Preventive Services Task Force (USPSTF)?
- A. Abdominal ultrasonography for abdominal aortic aneurysm
- B. Carcinoembryonic antigen for colorectal cancer
- C. Low-dose computerized tomography for lung cancer
- D. Colonoscopy for colorectal cancer (Correct Answer)
- E. Prostate-specific antigen for prostate cancer
Screening interval determination Explanation: **Colonoscopy for colorectal cancer**
- The **USPSTF recommends screening for colorectal cancer in adults aged 45 to 75 years**. This patient is 50 years old, placing him squarely within this recommended age range for colonoscopy, irrespective of smoking status or other risk factors.
- **Colonoscopy** is a highly effective screening tool for colorectal cancer, allowing for the detection and removal of precancerous polyps.
*Abdominal ultrasonography for abdominal aortic aneurysm*
- The **USPSTF recommends one-time screening for abdominal aortic aneurysm (AAA) with ultrasonography in men aged 65 to 75 years who have ever smoked**. This patient is 50 years old, falling outside the recommended age range for this screening, despite his smoking history.
- The benefit of screening for AAA is primarily for older men with a history of smoking, as the prevalence of AAA significantly increases with age.
*Low-dose computerized tomography for lung cancer*
- The **USPSTF recommends annual screening for lung cancer with low-dose computed tomography (LDCT) in adults aged 50 to 80 years who have a 20 pack-year smoking history and currently smoke or have quit within the past 15 years**. This patient has a 10-pack-year smoking history (10-15 cigarettes/day for 10 years ≈ 0.5-0.75 packs/day * 10 years = 5-7.5 pack-years), which does not meet the 20 pack-year threshold.
- While the patient is within the age range, his smoking history is insufficient to meet the criteria for routine lung cancer screening with LDCT.
*Carcinoembryonic antigen for colorectal cancer*
- **Carcinoembryonic antigen (CEA) is a tumor marker primarily used for monitoring the recurrence of colorectal cancer after treatment**, not for initial screening in asymptomatic individuals.
- The USPSTF and other guidelines do not recommend CEA as a screening test for colorectal cancer due to its low sensitivity and specificity in asymptomatic populations.
*Prostate-specific antigen for prostate cancer*
- The **USPSTF recommends that men aged 55 to 69 years should make an individual decision about being screened for prostate cancer with a prostate-specific antigen (PSA) test**, after discussing the potential benefits and harms with their clinician.
- This patient is 50 years old, which is younger than the age range where the USPSTF recommends shared decision-making for PSA screening.
Screening interval determination US Medical PG Question 7: A 46-year-old woman presents to her primary care physician for her annual examination. At her prior exam one year earlier, she had a Pap smear which was within normal limits. Which of the following health screenings is recommended for this patient?
- A. Colorectal screening (Correct Answer)
- B. Blood glucose and/or HbA1c screening
- C. Blood pressure at least once every 3 years
- D. Yearly Pap smear
- E. Bone mineral density screening
Screening interval determination Explanation: ***Colorectal screening***
- **Colorectal cancer screening** is generally recommended to start at age **45 years** for individuals at average risk.
- This patient is 46 years old, making immediate colorectal screening appropriate based on current guidelines.
*Blood glucose and/or HbA1c screening*
- **Blood glucose or HbA1c screening** for diabetes is recommended starting at age **35 for all adults** or earlier if there are risk factors such as obesity or a family history of diabetes.
- While this patient is 46, this screening should have already been initiated, and it is not the *most* uniquely recommended screening for this specific age that might have been overlooked.
*Blood pressure at least once every 3 years*
- **Blood pressure screening** should be performed **at least annually** for adults aged 40 and older, or more frequently if there are risk factors.
- Screening only every 3 years is insufficient for a 46-year-old patient.
*Yearly Pap smear*
- **Pap smear frequency** has changed; for women aged 30-65 with normal results, screening is recommended every **3 years** with cytology alone, or every 5 years with high-risk HPV testing alone or co-testing.
- A yearly Pap smear is no longer typical practice for a woman with normal prior results and no specific risk factors.
*Bone mineral density screening*
- **Bone mineral density (BMD) screening** for osteoporosis is typically recommended for women starting at age **65 years** or earlier if they have significant risk factors.
- This patient is 46 years old and has no mentioned risk factors, so BMD screening is not routinely indicated at this age.
Screening interval determination US Medical PG Question 8: A 19-year-old woman presents to the physician for a routine health maintenance examination. She has a past medical history of gastroesophageal reflux disease. She recently moved to a new city to begin her undergraduate studies. Her father was diagnosed with colon cancer at age 46. Her father's brother died because of small bowel cancer. Her paternal grandfather died because of stomach cancer. She takes a vitamin supplement. Current medications include esomeprazole and a multivitamin. She smoked 1 pack of cigarettes daily for 3 years but quit 2 years ago. She drinks 1–2 alcoholic beverages on the weekends. She appears healthy. Vital signs are within normal limits. Physical examination shows no abnormalities. Colonoscopy is unremarkable. Germline testing via DNA sequencing in this patient shows mutations in DNA repair genes MLH1 and MSH2. Which of the following will this patient most likely require at some point in her life?
- A. Celecoxib or sulindac therapy
- B. Surgical removal of a desmoid tumor
- C. Prophylactic proctocolectomy with ileoanal anastomosis
- D. Annual colonoscopy beginning at 20–25 years of age (Correct Answer)
- E. Measurement of carcinoembryonic antigen and CA 19-9 yearly
Screening interval determination Explanation: ***Annual colonoscopy beginning at 20–25 years of age***
- This patient's family history of multiple cancers at young ages (father with colon cancer at 46, uncle with small bowel cancer, grandfather with stomach cancer) combined with **germline mutations in MLH1 and MSH2** is highly indicative of **Lynch syndrome (hereditary non-polyposis colorectal cancer - HNPCC)**.
- Individuals with Lynch syndrome have a significantly increased risk of colorectal cancer, and screening with **annual colonoscopies starting at a young age (20-25 years or 2-5 years younger than the earliest age of diagnosis in the family)** is crucial for early detection and prevention.
*Celecoxib or sulindac therapy*
- **NSAID therapy** (like celecoxib or sulindac) is sometimes used for **chemoprevention in familial adenomatous polyposis (FAP)** to reduce polyp burden, especially in attenuated FAP.
- However, this patient's presentation and genetic findings point to **Lynch syndrome**, for which NSAID chemoprevention is not the primary or most effective strategy compared to surveillance.
*Surgical removal of a desmoid tumor*
- **Desmoid tumors** are benign but locally aggressive soft tissue tumors that are a characteristic **extracolonic manifestation of familial adenomatous polyposis (FAP)**, especially in patients with mutations in the APC gene.
- This patient has **Lynch syndrome**, which is associated with different extracolonic cancers (e.g., endometrial, ovarian, gastric, small bowel), but **desmoid tumors are not a typical feature of Lynch syndrome**.
*Prophylactic proctocolectomy with ileoanal anastomosis*
- **Prophylactic proctocolectomy** is the standard preventive surgery for individuals with **familial adenomatous polyposis (FAP)** to prevent the inevitable development of colorectal cancer due to hundreds to thousands of polyps.
- While Lynch syndrome carries a high risk of colorectal cancer, prophylactic colectomy is generally **not recommended as the initial management** given that surveillance via colonoscopy allows for removal of precancerous polyps and early-stage cancers, reserving surgery for when clinically indicated.
*Measurement of carcinoembryonic antigen and CA 19-9 yearly*
- **Carcinoembryonic antigen (CEA) and CA 19-9** are **tumor markers** that can be elevated in certain cancers (e.g., colorectal for CEA, pancreatic/biliary for CA 19-9).
- However, these markers have **poor sensitivity and specificity for screening healthy, asymptomatic individuals** at high risk for cancer and are primarily used for monitoring disease recurrence or treatment response in diagnosed cancers. They are not recommended for routine surveillance in Lynch syndrome.
Screening interval determination US Medical PG Question 9: A 28-year-old asymptomatic pregnant woman at 12 weeks gestation presents for prenatal care. She has no personal or family history of diabetes. Her BMI is 32 kg/m². She had a random glucose of 118 mg/dL at her first visit. She asks about gestational diabetes screening. Considering her risk factors and current pregnancy, what is the most appropriate screening approach?
- A. Perform 3-hour oral glucose tolerance test at 16 weeks
- B. Diagnose gestational diabetes based on random glucose and begin treatment
- C. Perform 1-hour glucose challenge test now
- D. Perform fasting glucose and hemoglobin A1c now to assess for preexisting diabetes (Correct Answer)
- E. Defer screening until 24-28 weeks gestation per routine protocol
Screening interval determination Explanation: ***Perform fasting glucose and hemoglobin A1c now to assess for preexisting diabetes***
- A **BMI ≥ 30 kg/m²** is a major risk factor necessitating early screening at the first prenatal visit to identify **pre-existing (overture) diabetes**.
- Identifying hyperglycemia early in pregnancy allows for immediate management to reduce the risk of **congenital anomalies** associated with pre-gestational diabetes.
*Perform 1-hour glucose challenge test now*
- While the **1-hour GCT** is a valid tool for early screening, standard biomarkers like **fasting plasma glucose** or **HbA1c** are also appropriate for detecting overt diabetes at the initial visit.
- The goal in the first trimester for high-risk patients is often to rule out **Type 2 Diabetes mellitus** that existed prior to pregnancy.
*Defer screening until 24-28 weeks gestation per routine protocol*
- Routine screening at **24-28 weeks** is reserved for women without significant risk factors; this patient's **obesity** mandates earlier evaluation.
- Delayed screening in obese patients may miss a window for intensive **glycemic control** during critical fetal organogenesis.
*Diagnose gestational diabetes based on random glucose and begin treatment*
- A **random glucose of 118 mg/dL** is within the normal range and is not diagnostic of either GDM (which requires >200 mg/dL with symptoms) or overt diabetes.
- Diagnosis requires structured testing such as an **HbA1c ≥ 6.5%**, fasting glucose ≥ 126 mg/dL, or a formal **oral glucose tolerance test (OGTT)**.
*Perform 3-hour oral glucose tolerance test at 16 weeks*
- The **3-hour OGTT** is typically the second step of a two-step screening process and is not indicated as an initial screening tool at 16 weeks.
- High-risk patients should be screened as soon as possible, often at the **first prenatal visit** (12 weeks in this case), rather than waiting until the second trimester.
Screening interval determination US Medical PG Question 10: A 66-year-old man underwent screening colonoscopy which revealed a 1.2 cm tubular adenoma with low-grade dysplasia in the sigmoid colon that was completely removed. He has no family history of colorectal cancer. His colonoscopy 8 years ago was normal. He asks about surveillance recommendations. Considering current guidelines and competing risks, what is the most appropriate surveillance interval?
- A. Annual fecal immunochemical testing
- B. Repeat colonoscopy in 3 years
- C. Repeat colonoscopy in 10 years
- D. Repeat colonoscopy in 1 year
- E. Repeat colonoscopy in 5-10 years (Correct Answer)
Screening interval determination Explanation: ***Repeat colonoscopy in 5-10 years***
- According to the **USMSTF 2020 guidelines**, patients with **1 to 2 small (<10 mm) tubular adenomas** should have a surveillance colonoscopy in **7-10 years**; however, for a single adenoma **≥ 10 mm** (like this 1.2 cm lesion) with low-grade dysplasia, the recommended interval is **5-10 years**.
- This recommendation balances the slightly higher risk of a **larger lesion** against the **low-grade pathology** and the patient's age and overall risk profile.
*Repeat colonoscopy in 10 years*
- A strictly **10-year interval** is reserved for patients with a **normal colonoscopy** or those with only **distal hyperplastic polyps**.
- While 10 years is the upper limit of the recommended range, the presence of a **1.2 cm adenoma** requires a surveillance designation rather than a standard screening interval.
*Repeat colonoscopy in 3 years*
- The **3-year interval** is indicated for **high-risk findings** such as **≥3 adenomas**, adenomas with **villous histology**, or those with **high-grade dysplasia**.
- This patient only had a single lesion with **low-grade dysplasia**, making 3-year surveillance an over-utilization of resources.
*Repeat colonoscopy in 1 year*
- A **1-year interval** is generally only indicated for cases of **incomplete resection**, piece-meal removal of large sessile polyps, or **inadequate bowel preparation**.
- It is not appropriate for a **completely removed** 1.2 cm tubular adenoma.
*Annual fecal immunochemical testing*
- **Fecal immunochemical testing (FIT)** is a primary **screening modality**, not a surveillance tool for patients who have already been diagnosed with adenomas via colonoscopy.
- Once an adenoma is identified, the patient enters a **colonoscopy-based surveillance** program to directly monitor for recurrent or advancing lesions.
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