Screening

Question 1

What is screening

Answer 1

Test on asymptomatic patients

• reduce future risk of illhealth
• indicate who is at high risk => further investigation needed and intervene early if needed

Question 2

Key terminology

• validity
• sensitivity
• specificity
• false positive
• false negative
• positive predictive value
• no needed to screen

Answer 2

Validity - distinguish between who has disease and not

Sensitivity - correctly identify disease +ve
Specificity - correctly identify disease -ve
False positive - incorrect +ve identification
False negative - incorrect -ve identification
PPV - % of correct identification/all positive results
NPV - % of correct identification/all negative results

No needed to screen - no of patients needed to screen to find 1 diseased person

Question 3

Pros and cons of screening

Answer 3

Pros

• early diagnosis, less radical treatment => resources saved, decreased mortality
• reassured with negative result

Cons

• economic burden
• psychological distress, tests can be uncomfortable, some involve carcinogenic exposure (Xray in mammogram)
• time consuming
• overdiagnosis

Question 4

Bias that affects the impact of screening

Answer 4

Healthy screening bias - people who come are generally healthier, richer, better educated

Lead time bias - apparent survival time is longer because disease was picked up earlier

Length time bias - screening picks up slow progressive disease, less likely to detect rapid aggressive cases

Question 5

Describe cervical smear tests

Answer 5

25-64 y/o
25-49 = every 3 years
50-64 = every 5 years

CI

• total hysterectomy
• during period

Collect abnormal cervical cells with small brush => test for HPV

• if abnormal => cytology
• intervention => coloposcopy

Question 6

Describe bowel cancer screening

Describe higher risk colorectal cancer screening

Answer 6

55 - flexible sigmoidoscopy offered

FIT - single stool sample from 60-74
-if high risk => full colonoscopy

FAP - annual colonoscopy from diagnosis until increasd polyp dev seen => risk reducing surgery
Lynch - regular colonscopy from 25-75

Question 7

Describe breast cancer screening

Describe higher risk breast screening

Answer 7

50-70, every 3 years for mammogram
-if abnormal => breast exam, US, needle biopsy. MRI

BRCA1/2 or other high risk genes eligible

• 30-40 - annual MRI
• 40-50 - annual MRI + mammogram
• 50+ - annual mammogram