Screening guidelines

Screening guidelines 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)

Screening guidelines 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.

Screening guidelines US Medical PG Question 2: A 68-year-old female presents to your office for her annual check-up. Her vitals are HR 85, T 98.8 F, RR 16, BP 125/70. She has a history of smoking 1 pack a day for 35 years, but states she quit five years ago. She had her last pap smear at age 64 and states all of her pap smears have been normal. She had her last colonoscopy at age 62, which was also normal. Which of the following is the next best test for this patient?

• A. Pap smear
• B. Chest radiograph
• C. Abdominal ultrasound
• D. Colonoscopy
• E. Chest CT scan (Correct Answer)

Screening guidelines Explanation: ***Chest CT scan*** - This patient is a 68-year-old female with a **35-pack-year smoking history** who quit 5 years ago, placing her in a high-risk group for lung cancer. - **Low-dose computed tomography (LDCT)** for lung cancer screening is recommended annually for individuals aged 50-80 with a 20-pack-year smoking history who currently smoke or have quit within the past 15 years. *Pap smear* - A Pap smear is not indicated as she had her last one at age 64 and all previous results were normal. - Guidelines recommend discontinuing Pap smears at age 65 if there is no history of moderate or severe dysplasia and three consecutive negative results within the last 10 years. *Chest radiograph* - A chest radiograph is a less sensitive and specific tool for detecting early lung cancer compared to LDCT. - It misses a significant proportion of early-stage lung cancers and is not recommended for lung cancer screening. *Abdominal ultrasound* - An abdominal ultrasound is generally used to screen for conditions like abdominal aortic aneurysm in specific high-risk populations (males 65-75 who have ever smoked). - There is no indication from the provided history for an abdominal ultrasound in this patient. *Colonoscopy* - This patient had a normal colonoscopy at age 62. - Current guidelines recommend repeating colonoscopy every 10 years if the previous one was normal, so she is not due for another one yet.

Screening guidelines US Medical PG Question 3: A genetic population study is being conducted to find the penetrance of a certain disease. This disease is associated with impaired iron metabolism and primarily affects the liver. Patients often present with diabetes and bronze skin pigmentation. After a genetic screening of 120 inhabitants with a family history of this disease, 40 were found to have the disease-producing genotype, but only 10 presented with symptoms. What are the chances of the screened patients with said genotype developing the disease phenotype?

• A. 0.4%
• B. 40%
• C. 3%
• D. 4%
• E. 25% (Correct Answer)

Screening guidelines Explanation: ***25%*** - **Penetrance** is calculated as the proportion of individuals with a specific genotype who express the associated phenotype. - In this case, 10 individuals out of 40 with the disease-producing genotype developed symptoms, so (10 / 40) * 100% = **25%**. *0.4%* - This value is significantly lower than the actual penetrance and likely results from an incorrect calculation or misinterpretation of the given data. - It does not accurately reflect the proportion of genotypically affected individuals who express the phenotype. *40%* - This percentage represents the proportion of screened individuals with the disease-producing genotype (40 out of 120 are ~33%), not the penetrance itself. - It incorrectly equates the presence of the genotype in the population with the expression of the phenotype. *3%* - This value is likely obtained by an erroneous calculation, possibly by dividing the symptomatic individuals by the total screened population (10/120 ≈ 8.3%), which does not represent penetrance. - It does not account for the specific individuals who possess the genotype. *4%* - This percentage might arise from an incorrect division or a misunderstanding of what constitutes penetrance. - It is an inaccurate representation of the ratio between phenotype expression and genotype presence.

Screening guidelines US Medical PG Question 4: You conduct a medical research study to determine the screening efficacy of a novel serum marker for colon cancer. The study is divided into 2 subsets. In the first, there are 500 patients with colon cancer, of which 450 are found positive for the novel serum marker. In the second arm, there are 500 patients who do not have colon cancer, and only 10 are found positive for the novel serum marker. What is the overall sensitivity of this novel test?

• A. 450 / (450 + 10)
• B. 490 / (10 + 490)
• C. 490 / (50 + 490)
• D. 450 / (450 + 50) (Correct Answer)
• E. 490 / (450 + 490)

Screening guidelines Explanation: ***450 / (450 + 50)*** - **Sensitivity** is defined as the proportion of actual positive cases that are correctly identified by the test. - In this study, there are **500 patients with colon cancer** (actual positives), and **450 of them tested positive** for the marker, while **50 tested negative** (500 - 450 = 50). Therefore, sensitivity = 450 / (450 + 50) = 450/500 = 0.9 or 90%. *450 / (450 + 10)* - This formula represents **Positive Predictive Value (PPV)**, which is the probability that a person with a positive test result actually has the disease. - It incorrectly uses the total number of **test positives** in the denominator (450 true positives + 10 false positives) instead of the total number of diseased individuals, which is needed for sensitivity. *490 / (10 + 490)* - This is actually the correct formula for **specificity**, not sensitivity. - Specificity = TN / (FP + TN) = 490 / (10 + 490) = 490/500 = 0.98 or 98%, which measures the proportion of actual negative cases correctly identified. - The question asks for sensitivity, not specificity. *490 / (50 + 490)* - This formula incorrectly mixes **true negatives (490)** with **false negatives (50)** in an attempt to calculate specificity. - The correct specificity formula should use false positives (10), not false negatives (50), in the denominator: 490 / (10 + 490). *490 / (450 + 490)* - This calculation incorrectly combines **true negatives (490)** and **true positives (450)** in the denominator, which does not correspond to any standard epidemiological measure. - Neither sensitivity nor specificity uses both true positives and true negatives in the denominator.

Screening guidelines US Medical PG Question 5: 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 guidelines 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 guidelines Flashcard 1 of 5

Question: One use of Mammography as a screening tool is to detect invasive carcinoma before it becomes _____

Answer: clinically palpable

Screening guidelines Flashcard 2 of 5

Question: What *used to be* the rule out test for HIV?_____

Answer: ELISA

Screening guidelines Flashcard 3 of 5

Question: One positive screening test for Cushing syndrome is an increased midnight _____ cortisol

Answer: salivary

Screening guidelines Flashcard 4 of 5

Question: What test is used to screen for infectious mononucleosis? _____

Answer: Monospot test

Screening guidelines Flashcard 5 of 5

Question: Which glucose test is preferred for general use?_____

Answer: Fasting glucose