Screening

Question 1

Screening:

Answer 1

Testing
ex) questions, physical exams, labs, etc.) asymptomatic people

Examples:
-“Annual Physical”
-Periodic: colonoscopies, gynecological exams, mammograms, PSA

Question 2

Purpose and potential benefits:

Answer 2

-Detect diseases that are better treated before signs and symptoms show up and prevent people from suffering with or dying from them
ex) (in theory) PSA for prostate cancer

-Use knowledge of risk factors for disease to prevent or decrease the burden of the disease by modifying the risk factors
ex) lipid panels for cardiovascular disease

-US preventative task force (USPSTF) screening recommendations

Question 3

Important factors:
For best results:
The disease should be…

Answer 3

A significant public health problem
ex) common and/or significant morbidity and/or mortality

Treatable with these stipulations:
-the potential for cure increases with early detection
-Treatment is easily available

Question 4

Important factors:
For best results:
The test should be…

Answer 4

-sensitive to pre-clinical disease
-safe
-inexpensive
-easily accessible/available
-lead to demonstrated improved health outcomes

Question 5

Pseudodisease:

Answer 5

a condition detected by screeing that does not require treatment because it will not adversely affect the patients life.

Type I: conditions that might not progress to symptomatic disease and may even regress
ex) ductal carcinoma in situ

Type II: slowly progressive disease (conditions with a long detectable preclinical phase)
-patient would “die with it, not from it”
ex) prostate cancer, often

If treated, patient may be considered “cured” despite the fact that even if untreated, the condition would not have killed them before they died of something else

Question 6

Screen chart:

Answer 6

Question 7

Bayesiin principles:

Answer 7

Unlike when a patient arrives with a concern, screening applies tests to ostensibly healthy people.
-pretest probability is therefore usually very low

Consider (screening mammography)
-pretest probability (screening clinic): 3%
-Sensitivity: 80%
-Specificity: 90%
-LR+: 8
-LR-: 0.22
-Post-test probability if positive: 20%
-Post test probability if negative: 0.7%

Question 8

Harms of screening:

Answer 8

Harms of tests (radiation, perforation from colonoscopy, cost, time)

False positives:
-Psychological burden
-Further testing (over-testing)
-Over-treatment
(even “safe” treatments impose burden, financial and otherwise)

Question 9

Summary:

Answer 9

1) screening means testing people for conditions even when their asymptomatic

2) The goal of screening is to prevent disease or treat it early to minimize disease harms

3) A number if features of the disease and test determine the value of the screening

4) Advantages of screening include disease prevention and early treatment. Disadvantages include over-testing and over-treatment

5) Particularly low pretest probabilities are a significant factor when interpreting the results of a screening test

6) Screening represents a balance between cases in which it may be possible to change the outcome and those in which we are causing a net harm (overdiagnosis)