Refinement of differential with testing US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Refinement of differential with testing. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Refinement of differential with testing US Medical PG Question 1: A scientist in Chicago is studying a new blood test to detect Ab to EBV with increased sensitivity and specificity. So far, her best attempt at creating such an exam reached 82% sensitivity and 88% specificity. She is hoping to increase these numbers by at least 2 percent for each value. After several years of work, she believes that she has actually managed to reach a sensitivity and specificity much greater than what she had originally hoped for. She travels to China to begin testing her newest blood test. She finds 2,000 patients who are willing to participate in her study. Of the 2,000 patients, 1,200 of them are known to be infected with EBV. The scientist tests these 1,200 patients' blood and finds that only 120 of them tested negative with her new exam. Of the patients who are known to be EBV-free, only 20 of them tested positive. Given these results, which of the following correlates with the exam's specificity?
- A. 82%
- B. 90%
- C. 84%
- D. 86%
- E. 98% (Correct Answer)
Refinement of differential with testing Explanation: ***98%***
- **Specificity** measures the proportion of **true negatives** among all actual negatives.
- In this case, 800 patients are known to be EBV-free (actual negatives), and 20 of them tested positive (false positives). This means 800 - 20 = 780 tested negative (true negatives). Specificity = (780 / 800) * 100% = **98%**.
*82%*
- This value represents the *original sensitivity* before the scientist’s new attempts to improve the test.
- It does not reflect the *newly calculated specificity* based on the provided data.
*90%*
- This value represents the *newly calculated sensitivity* of the test, not the specificity.
- Out of 1200 EBV-infected patients, 120 tested negative (false negatives), meaning 1080 tested positive (true positives). Sensitivity = (1080 / 1200) * 100% = 90%.
*84%*
- This percentage is not directly derived from the information given for either sensitivity or specificity after the new test results.
- It does not correspond to any of the calculated values for the new test's performance.
*86%*
- This percentage is not directly derived from the information given for either sensitivity or specificity after the new test results.
- It does not correspond to any of the calculated values for the new test's performance.
Refinement of differential with testing US Medical PG Question 2: An infectious disease investigator is evaluating the diagnostic accuracy of a new interferon-gamma-based assay for diagnosing tuberculosis in patients who have previously received a Bacillus Calmette-Guérin (BCG) vaccine. Consenting participants with a history of BCG vaccination received an interferon-gamma assay and were subsequently evaluated for tuberculosis by sputum culture. Results of the study are summarized in the table below.
Tuberculosis, confirmed by culture No tuberculosis Total
Positive interferon-gamma assay 90 6 96
Negative interferon-gamma assay 10 194 204
Total 100 200 300
Based on these results, what is the sensitivity of the interferon-gamma-based assay for the diagnosis of tuberculosis in this study?
- A. 90/96
- B. 100/300
- C. 194/200
- D. 90/100 (Correct Answer)
- E. 194/204
Refinement of differential with testing Explanation: ***90/100***
- **Sensitivity** measures the proportion of **true positive** cases that are correctly identified by the test.
- In this study, there are 90 true positive results (positive interferon-gamma assay in patients with confirmed tuberculosis) out of a total of 100 individuals with confirmed tuberculosis (90 + 10).
*90/96*
- This calculation represents the **positive predictive value** (90 true positives / 96 total positive tests).
- It answers the question: "If the test is positive, what is the likelihood that the patient actually has the disease?"
*100/300*
- This value represents the prevalence of tuberculosis in the study population (100 confirmed cases / 300 total participants).
- It does not reflect a measure of the test's diagnostic accuracy.
*194/200*
- This value represents the **specificity** of the test (194 true negatives / 200 total individuals without tuberculosis).
- Specificity measures the proportion of true negative cases that are correctly identified by the test.
*194/204*
- This calculation represents the **negative predictive value** (194 true negatives / 204 total negative tests).
- It answers the question: "If the test is negative, what is the likelihood that the patient does not have the disease?"
Refinement of differential with testing US Medical PG Question 3: A mother presents to the family physician with her 16-year-old son. She explains, "There's something wrong with him doc. His grades are getting worse, he's cutting class, he's gaining weight, and his eyes are often bloodshot." Upon interviewing the patient apart from his mother, he seems withdrawn and angry at times when probed about his social history. The patient denies abuse and sexual history. What initial test should be sent to rule out the most likely culprit of this patient's behavior?
- A. Complete blood count
- B. Sexually transmitted infection (STI) testing
- C. Blood culture
- D. Urine toxicology screen (Correct Answer)
- E. Slit lamp examination
Refinement of differential with testing Explanation: ***Urine toxicology screen***
- The patient's presentation with **declining grades**, **cutting class**, **weight gain**, **bloodshot eyes**, and **irritability** are classic signs of **substance abuse** in an adolescent.
- A **urine toxicology screen** is the most appropriate initial test to detect common illicit substances, especially given the clear signs pointing towards drug use.
*Slit lamp examination*
- This test is used to examine the **anterior segment of the eye**, including the conjunctiva, cornea, iris, and lens.
- While the patient has **bloodshot eyes**, this specific test would be more relevant for ruling out ocular infections or injuries, not for diagnosing the underlying cause of systemic behavioral changes.
*Complete blood count*
- A **complete blood count (CBC)** measures different components of the blood, such as red blood cells, white blood cells, and platelets.
- A CBC is a general health indicator and while it can detect infections or anemia, it is not specific or sensitive enough to identify the cause of the behavioral changes described.
*Sexually transmitted infection (STI) testing*
- Although the patient denies sexual history, all adolescents presenting with certain risk factors or symptoms may warrant STI testing in a broader health assessment.
- However, in this scenario, the primary cluster of symptoms (poor grades, cutting class, bloodshot eyes, irritability) points more directly to substance abuse than to an STI.
*Blood culture*
- A **blood culture** is used to detect the presence of bacteria or other microorganisms in the bloodstream, indicating a systemic infection (sepsis).
- The patient's symptoms are not indicative of an acute bacterial bloodstream infection, and a blood culture would not be the initial test for the presented behavioral changes.
Refinement of differential with testing US Medical PG Question 4: A geriatric investigator is evaluating the consistency of Alzheimer dementia diagnoses based on clinical symptoms. Patients with known chart diagnoses of Alzheimer dementia were evaluated by multiple physicians during a fixed time interval. Each evaluator was blinded to the others' assessments. The extent to which the diagnosis by one physician was replicated by another clinician examining the same patient is best described by which of the following terms?
- A. Validity
- B. Specificity
- C. Predictive value
- D. Sensitivity
- E. Precision (Correct Answer)
Refinement of differential with testing Explanation: ***Precision***
- **Precision** refers to the consistency or reproducibility of a measurement or diagnosis. When multiple physicians reach the same diagnosis for the same patient, it indicates high precision.
- In this context, it specifically assesses **inter-rater reliability**, which is the extent to which different observers agree on the same assessment.
*Validity*
- **Validity** refers to the extent to which a test or measure accurately assesses what it is intended to measure. It is about the "truthfulness" of the diagnosis.
- While important for diagnosis, validity is about accuracy against a gold standard, not consistency among different observers.
*Specificity*
- **Specificity** is the ability of a test to correctly identify individuals who do *not* have the disease (true negatives).
- It measures the proportion of healthy individuals who are correctly identified as healthy by the test, which is not what is being evaluated here.
*Predictive value*
- **Predictive value** assesses the probability that a person *actually has* (positive predictive value) or *does not have* (negative predictive value) a disease given their test result.
- This concept relates to the diagnostic utility of a test in a population, not the consistency of different clinician diagnoses.
*Sensitivity*
- **Sensitivity** is the ability of a test to correctly identify individuals who *do* have the disease (true positives).
- It measures the proportion of diseased individuals who are correctly identified as diseased by the test, which is distinct from inter-rater agreement.
Refinement of differential with testing US Medical PG Question 5: A 25-year-old man comes to the physician for severe back pain. He describes the pain as shooting and stabbing. On a 10-point scale, he rates the pain as a 9 to 10. The pain started after he lifted a heavy box at work; he works at a supermarket and recently switched from being a cashier to a storekeeper. The patient appears to be in severe distress. Vital signs are within normal limits. On physical examination, the spine is nontender without paravertebral muscle spasms. Range of motion is normal. A straight-leg raise test is negative. After the physical examination has been completed, the patient asks for a letter to his employer attesting to his inability to work as a storekeeper. Which of the following is the most appropriate response?
- A. “Yes. Since work may worsen your condition, I would prefer that you stay home a few days. I will write a letter to your employer to explain the situation.”
- B. You say you are in severe pain. However, the physical examination findings do not suggest a physical problem that can be addressed with medications or surgery. I'd like to meet on a regular basis to see how you're doing.
- C. I understand that you are uncomfortable, but the findings do not match the severity of your symptoms. Let's talk about the recent changes at your job. (Correct Answer)
- D. The physical exam findings do not match your symptoms, which suggests a psychological problem. I would be happy to refer you to a mental health professional.
- E. The physical exam findings suggest a psychological rather than a physical problem. But there is a good chance that we can address it with cognitive-behavioral therapy.
Refinement of differential with testing Explanation: ***"I understand that you are uncomfortable, but the findings do not match the severity of your symptoms. Let's talk about the recent changes at your job."***
- This response acknowledges the patient's reported discomfort while gently highlighting the **discrepancy between symptoms and objective findings**, which is crucial in cases of suspected **somatoform or functional pain**.
- It also opens communication about potential **psychosocial stressors** related to his job change, which could be contributing to his symptoms, without dismissing his pain or making a premature diagnosis.
*"You say you are in severe pain. However, the physical examination findings do not suggest a physical problem that can be addressed with medications or surgery. I'd like to meet on a regular basis to see how you're doing."*
- While this option correctly identifies the lack of physical findings, it can be perceived as dismissive of the patient's pain, potentially damaging the **physician-patient relationship**.
- Suggesting regular meetings without a clear plan for addressing his immediate concerns or exploring underlying issues might not be the most effective initial approach.
*“Yes. Since work may worsen your condition, I would prefer that you stay home a few days. I will write a letter to your employer to explain the situation.”*
- This response would **validate the patient's claim of severe pain** without objective evidence, potentially reinforcing illness behavior and avoiding addressing the underlying issue.
- Providing a doctor's note for inability to work without a clear diagnostic basis or understanding of the pain's origin is **medically inappropriate** and could set a precedent for future such requests.
*"The physical exam findings do not match your symptoms, which suggests a psychological problem. I would be happy to refer you to a mental health professional."*
- Directly labeling the problem as "psychological" can be **stigmatizing and alienating** to the patient, leading to distrust and resistance to care.
- While a psychological component might be present, immediately referring to mental health without further exploration of the patient's situation or current stressors is premature and lacks empathy.
*"The physical exam findings suggest a psychological rather than a physical problem. But there is a good chance that we can address it with cognitive-behavioral therapy."*
- Similar to the previous option, explicitly stating a "psychological problem" can be **stigmatizing**.
- Jumping directly to recommending **cognitive-behavioral therapy (CBT)** without a comprehensive discussion and patient buy-in is premature and may lead to non-compliance.
Refinement of differential with testing US Medical PG Question 6: A 28-year-old woman dies shortly after receiving a blood transfusion. Autopsy reveals widespread intravascular hemolysis and acute renal failure. Investigation reveals that she received type A blood, but her medical record indicates she was type O. In a malpractice lawsuit, which of the following elements must be proven?
- A. Duty, breach, causation, and damages (Correct Answer)
- B. Only duty and breach
- C. Only breach and causation
- D. Duty, breach, and damages
Refinement of differential with testing Explanation: ***Duty, breach, causation, and damages***
- In a medical malpractice lawsuit, all four elements—**duty, breach, causation, and damages**—must be proven for a successful claim.
- The healthcare provider had a **duty** to provide competent care, they **breached** that duty by administering the wrong blood type, this breach **caused** the patient's death and renal failure, and these injuries constitute **damages**.
*Only duty and breach*
- While **duty** and **breach** are necessary components, proving only these two is insufficient for a malpractice claim.
- It must also be demonstrated that the breach directly led to the patient's harm and resulted in legally recognized damages.
*Only breach and causation*
- This option omits the crucial elements of professional **duty** owed to the patient and the resulting **damages**.
- A claim cannot succeed without establishing that a duty existed and that quantifiable harm occurred.
*Duty, breach, and damages*
- This option misses the critical element of **causation**, which links the provider's breach of duty to the patient's injuries.
- Without proving that the breach *caused* the damages, even if a duty was owed and breached, and damages occurred, the claim would fail.
Refinement of differential with testing US Medical PG Question 7: 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
Refinement of differential with testing 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.
Refinement of differential with testing US Medical PG Question 8: A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?
- A. "Does the diarrhea typically precede the constipation, or vice-versa?"
- B. "Is the diarrhea foul-smelling?"
- C. "Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"
- D. "Are the symptoms worse in the morning or at night?"
- E. "Can you tell me more about the symptoms you have been experiencing?" (Correct Answer)
Refinement of differential with testing Explanation: ***Can you tell me more about the symptoms you have been experiencing?***
- This **open-ended question** encourages the patient to provide a **comprehensive narrative** of their symptoms, including details about onset, frequency, duration, alleviating/aggravating factors, and associated symptoms, which is crucial for diagnosis.
- In a patient presenting with vague, intermittent symptoms like alternating constipation and diarrhea, allowing them to elaborate freely can reveal important clues that might not be captured by more targeted questions.
*Does the diarrhea typically precede the constipation, or vice-versa?*
- While knowing the sequence of symptoms can be helpful in understanding the **pattern of bowel dysfunction**, it is a very specific question that might overlook other important aspects of the patient's experience.
- It prematurely narrows the focus without first obtaining a broad understanding of the patient's overall symptomatic picture.
*Is the diarrhea foul-smelling?*
- Foul-smelling diarrhea can indicate **malabsorption** or **bacterial overgrowth**, which are important to consider in some gastrointestinal conditions.
- However, this is a **specific symptom inquiry** that should follow a more general exploration of the patient's symptoms, as it may not be relevant if other crucial details are missed.
*Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life*
- Quantifying pain intensity is useful for assessing the **severity of discomfort** and monitoring changes over time.
- However, for a patient with intermittent rather than acute, severe pain, understanding the **character, location, and triggers** of the pain is often more diagnostically valuable than just a numerical rating initially.
*Are the symptoms worse in the morning or at night?*
- Diurnal variation can be relevant in certain conditions, such as inflammatory bowel diseases where nocturnal symptoms might be more concerning, or functional disorders whose symptoms might be stress-related.
- This is another **specific question** that should come after gathering a more complete initial picture of the patient's symptoms to ensure no key information is overlooked.
Refinement of differential with testing US Medical PG Question 9: A family doctor in a rural area is treating a patient for dyspepsia. The patient had chronic heartburn and abdominal pain for the last 2 months and peptic ulcer disease due to a suspected H. pylori infection. For reasons relating to affordability and accessibility, the doctor decides to perform a diagnostic test in the office that is less invasive and more convenient. Which of the following is the most likely test used?
- A. Steiner's stain
- B. Culture of organisms from gastric specimen
- C. Stool antigen test (Correct Answer)
- D. Detection of the breakdown products of urea in biopsy
- E. Serology (ELISA testing)
Refinement of differential with testing Explanation: ***Stool antigen test***
- This **non-invasive** and **cost-effective** test detects *H. pylori* antigens in stool, making it suitable for a rural setting with limited resources.
- It is highly sensitive and specific, useful for both initial diagnosis and confirming eradication after treatment.
*Steiner's stain*
- **Steiner's stain** (Steiner silver stain) is primarily used for histological visualization of *Legionella* species, and **not for** *H. pylori* detection in routine clinical practice.
- It requires an **endoscopic biopsy**, making it more invasive and costly than the stool antigen test.
*Culture of organisms from gastric specimen*
- This method requires an **endoscopic biopsy** and specialized culture facilities, which may not be available in a rural doctor's office.
- It is more expensive and time-consuming, and primarily used when **antibiotic resistance** is suspected.
*Detection of the breakdown products of urea in biopsy*
- This refers to the **rapid urease test** (e.g., CLOtest), which is performed on a **gastric biopsy** obtained during endoscopy.
- While quick, it is an **invasive procedure** requiring endoscopy, which contradicts the patient's and doctor's preferences for a less invasive test.
*Serology (ELISA testing)*
- **Serology** detects antibodies to *H. pylori* but cannot differentiate between **active infection** and **past exposure**.
- Its utility in monitoring eradication is limited, and it's generally not recommended as the primary diagnostic test due to its inability to confirm active infection.
Refinement of differential with testing US Medical PG Question 10: A 57-year-old woman comes to the physician because of a 6-month history of tinnitus and progressive hearing loss in the left ear. She has type 2 diabetes mellitus and Raynaud syndrome. Her current medications include metformin, nifedipine, and a multivitamin. She appears well. Vital signs are within normal limits. Physical examination shows no abnormalities. A vibrating tuning fork is placed on the left mastoid process. Immediately after the patient does not hear a tone, the tuning fork is held over the left ear and she reports hearing the tuning fork again. The same test is repeated on the right side and shows the same pattern. The vibration tuning fork is then placed on the middle of the forehead and the patient hears the sound louder in the right ear. Which of the following is the most likely diagnosis?
- A. Acoustic neuroma (Correct Answer)
- B. Meningioma
- C. Cerumen impaction
- D. Ménière disease
- E. Presbycusis
Refinement of differential with testing Explanation: ***Acoustic neuroma***
- The patient presents with **unilateral tinnitus** and **progressive sensorineural hearing loss** in the left ear, which is a classic presentation of an acoustic neuroma.
- The **Rinne test** results (air conduction > bone conduction bilaterally) indicate **no conductive hearing loss**, while the **Weber test lateralizing to the right ear** confirms **sensorineural hearing loss in the left ear**.
*Meningioma*
- While a meningioma could present with neurological symptoms, it typically does not selectively cause **unilateral tinnitus** and **hearing loss** in this specific pattern without other focal neurological deficits.
- Meningiomas are usually **slow-growing** and would likely present with mass effect symptoms, such as headache or seizures, depending on their location, which are not described here.
*Cerumen impaction*
- **Cerumen impaction** would cause a **conductive hearing loss**, where bone conduction would be *louder* than air conduction on the Rinne test (BC > AC).
- The patient's Rinne test results (AC > BC) are consistent with **sensorineural hearing loss**, not conductive.
*Ménière disease*
- **Ménière disease** is characterized by episodic **vertigo, tinnitus, fluctuating hearing loss**, and aural fullness.
- The patient's symptoms are primarily **progressive hearing loss** and constant tinnitus, without the episodic vertigo typical of Ménière disease.
*Presbycusis*
- **Presbycusis** is **age-related bilateral sensorineural hearing loss**, typically symmetric and affecting high frequencies.
- The patient's symptoms are **unilateral** (affecting the left ear predominantly) and present with specific tuning fork findings that point to a localized lesion rather than general aging.
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