Screening tests

Screening tests US Medical PG Question 1: Group of 100 medical students took an end of the year exam. The mean score on the exam was 70%, with a standard deviation of 25%. The professor states that a student's score must be within the 95% confidence interval of the mean to pass the exam. Which of the following is the minimum score a student can have to pass the exam?

• A. 45%
• B. 63.75%
• C. 67.5%
• D. 20%
• E. 65% (Correct Answer)

Screening tests Explanation: ***65%*** - To find the **95% confidence interval (CI) of the mean**, we use the formula: Mean ± (Z-score × Standard Error). For a 95% CI, the Z-score is approximately **1.96**. - The **Standard Error (SE)** is calculated as SD/√n, where n is the sample size (100 students). So, SE = 25%/√100 = 25%/10 = **2.5%**. - The 95% CI is 70% ± (1.96 × 2.5%) = 70% ± 4.9%. The lower bound is 70% - 4.9% = **65.1%**, which rounds to **65%** as the minimum passing score. *45%* - This value is significantly lower than the calculated lower bound of the 95% confidence interval (approximately 65.1%). - It would represent a score far outside the defined passing range. *63.75%* - This value falls below the calculated lower bound of the 95% confidence interval (approximately 65.1%). - While close, this score would not meet the professor's criterion for passing. *67.5%* - This value is within the 95% confidence interval (65.1% to 74.9%) but is **not the minimum score**. - Lower scores within the interval would still qualify as passing. *20%* - This score is extremely low and falls significantly outside the 95% confidence interval for a mean of 70%. - It would indicate performance far below the defined passing threshold.

Screening tests US Medical PG Question 2: A 32-year-old woman makes an appointment with her family physician for a new-employment physical examination. She has no complaints and the physical examination is unremarkable. The family history is negative for malignancies and inherited disorders. During the visit, she provides the results of a Pap smear taken last week, which reports the presence of atypical squamous cells of undetermined significance (ASC-US), along with a test for HPV, which was negative. The previous Pap smear was normal (negative for intraepithelial lesions or malignancy). When would you recommend that she have another Pap smear?

• A. 3 years (Correct Answer)
• B. 1 year
• C. Immediately
• D. 6 months
• E. 5 years

Screening tests Explanation: ***3 years*** - For women aged 21-65 with an **ASC-US Pap result AND a negative HPV test**, current guidelines recommend routine **co-testing every 3 years** or cytology alone every 3 years. - A negative HPV test in the setting of ASC-US indicates a very low risk of high-grade disease, allowing for a return to routine screening intervals. *1 year* - A 1-year follow-up would typically be recommended for an **ASC-US Pap result** when the **HPV test is positive**, or if HPV testing was not performed. - This shorter interval is appropriate when there's an increased risk of underlying cervical dysplasia. *Immediately* - Immediate repeat testing is generally reserved for more concerning findings, such as **high-grade squamous intraepithelial lesions (HSIL)**, atypical glandular cells (AGC), or frankly malignant results. - ASC-US with negative HPV does not warrant immediate re-evaluation. *6 months* - A 6-month follow-up is not a standard recommendation for an **ASC-US with a negative HPV test**. - It might be considered in specific circumstances for an ASC-US result with a positive HPV test, but not when HPV is negative. *5 years* - Routine screening with **co-testing (Pap and HPV)** is typically recommended every **5 years** for women aged 30-65 with **normal Pap and negative HPV results**. - This patient has an ASC-US result, which necessitates a slightly shorter follow-up than routine screening.

Screening tests US Medical PG Question 3: 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 tests 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 tests US Medical PG Question 4: A group of gastroenterologists is concerned about low colonoscopy screening rates. They decide to implement a free patient navigation program to assist local residents and encourage them to obtain colonoscopies in accordance with U.S. Preventive Services Task Force (USPSTF) guidelines. Local residents were recruited at community centers. Participants attended monthly meetings with patient navigators and were regularly reminded that their adherence to screening guidelines was being evaluated. Colonoscopy screening rates were assessed via chart review, which showed that 90% of participants adhered to screening guidelines. Data collected via chart review for local residents recruited at community centers who did not participate in the free patient navigation system found that 34% of that population adhered to USPSTF guidelines. Which of the following has most likely contributed to the observed disparity in colonoscopy screening rates?

• A. Recall bias
• B. Confirmation bias
• C. Reporting bias
• D. Hawthorne effect (Correct Answer)
• E. Sampling bias

Screening tests Explanation: ***Hawthorne effect*** - The **Hawthorne effect** is a type of reactivity in which individuals modify an aspect of their behavior in response to their awareness of being observed. - In this study, participants were aware that their adherence to screening guidelines was being evaluated, likely leading to increased compliance simply due to this awareness rather than the efficacy of the patient navigation program alone. *Recall bias* - **Recall bias** occurs when participants disproportionately remember or inaccurately recall past events, often due to their current health status or beliefs. - This bias is less likely here as colonoscopy screening rates were assessed via **chart review**, an objective measure, rather than participant self-report. *Confirmation bias* - **Confirmation bias** is the tendency to search for, interpret, favor, and recall information in a way that confirms one's preexisting beliefs or hypotheses. - This bias typically affects the researchers or observers, not the participants' behavior in the observed manner, as the question focuses on the participants' increased screening rates. *Reporting bias* - **Reporting bias** refers to selective revealing or suppression of information during the reporting of research findings, and can occur when study participants selectively report symptoms or behaviors. - While participants might selectively report, the data here was gathered through **chart review**, which is a more objective measure of actual behavior, making reporting bias less likely to explain the disparity in screening rates. *Sampling bias* - **Sampling bias** occurs when a sample is not representative of the population from which it is drawn, leading to skewed results. - While there might be some sampling bias in who chose to participate in the free program, the observed disparity is specifically about behavior change in those *being observed*, pointing more strongly to the Hawthorne effect.

Screening tests US Medical PG Question 5: A 58-year-old woman presents to the physician for a routine gynecological visit. She denies any acute issues and remarks that she has not been sexually active for the past year. Her last Pap test was negative for any abnormal cytology. A pelvic examination and Pap test is performed at the current visit with no remarkable findings. Which of the following approaches to cervical cancer screening is most appropriate for this patient?

• A. Colposcopy in 3 years
• B. Pap test and HPV test in 5 years (Correct Answer)
• C. Pap test only in 5 years
• D. Discontinue screening until the patient becomes sexually active
• E. Colposcopy at the current visit to verify Pap test results

Screening tests Explanation: ***Pap test and HPV test in 5 years*** - For women aged 30-65, **co-testing with both a Pap test and HPV test every 5 years** is the preferred screening interval if both results are normal. - This patient, at 58 years old, falls within this age range, and her prior normal Pap tests along with a normal current one, support a 5-year interval for co-testing. *Colposcopy in 3 years* - **Colposcopy** is a diagnostic procedure performed to further evaluate abnormal Pap test results, not a routine screening method. - Doing a colposcopy in 3 years would be an overly aggressive approach given her history of normal screenings. *Pap test only in 5 years* - While a Pap test alone every 3 years is an acceptable screening option, **co-testing with HPV every 5 years** is generally preferred due to its higher sensitivity for detecting precancerous lesions. - Omitting the HPV test would reduce the effectiveness of the screening strategy in detecting cervical cancer early. *Discontinue screening until the patient becomes sexually active* - **Sexual activity** is a risk factor for HPV infection, but cervical cancer screening guidelines do not link its discontinuation to a lack of sexual activity. - Women over 65 years old with a history of adequate negative screenings may discontinue screening, but this patient is 58 and does not meet that criterion yet. *Colposcopy at the current visit to verify Pap test results* - A **colposcopy** is indicated for **abnormal Pap test results**, which this patient does not have. - Performing a colposcopy in the absence of abnormal findings is unnecessary and not part of routine screening.

Screening tests Flashcard 1 of 5

Question: What is the key risk factor for Cervical Carcinoma?_____

Answer: High-risk HPV (16, 18, 31, 33)

Screening tests Flashcard 2 of 5

Question: What is the gold standard procedure for screening for Cervical Carcinoma?_____

Answer: Pap Smear

Screening tests Flashcard 3 of 5

Question: cervical dysplasia/squamous cell carcinoma

Answer: HPV 16, 18

Extra Information: koilocytes (enlarged, hyperchromatic epithelial cells) on Pap smear. (normal left, abnormal right) multiple sexual partners, smoking, early age of firts intercourse, HIV infectionmay progress to invasive carcinoma

Screening tests Flashcard 4 of 5

Question: Worldwide, _____ cancer is the most common gynecologic tumor.

Answer: cervical

Screening tests Flashcard 5 of 5

Question: secondary prevention (epidemiology)

Answer: early detection (e.g. Pap smear)