HaDSoc 6.1 Screening

Question 1

What are the different forms of detection of a disease?

Answer 1

• spontaneous presentation (the patient presents to GP/A&E etc because of symptoms)
• opportunistic finding- a patient will present to healthcare with one thing, then the professional will test for other things whilst they are there, and may find other problems eg hypertension.
• screening- asymptomatic pateint gets screened to see if they probably do/dont have a disease.

Question 2

describe features of screening:

Answer 2

• done on asymptomatic patients
• rapidly applied
• tells you whether you probably do/dont have a disease.

Question 3

Define screening:

Answer 3

Process of identifying healthy people who may be at increased risk of a disease.
Information, further tests and treatment is offered to reduce associated risks/complications.

Question 4

What is the main purpose of screening?

Answer 4

To improve the prognosis of the disease if it gets picked up. To give a better outcome

(Not just to detect it earlier)

Question 5

Give examples of population screening programs.

Answer 5

• bowel cancer
• breast cancer
• cervical cancer
• diabetic eye screening
• newborn blood spot.

Question 6

What are the 5 criteria which help you decide if screening is appropriate?

Answer 6

• condition
• tests
• intervention
• screening program
• implementation

Question 7

What features about the condition need to be considered when thinking about screening?

Answer 7

• is it prevelant (wont screen for something that only a few people have)
• is it severe enough to warrant screening
• have all the cost effective primary interventions been implimented beforehand?

Question 8

What features of the test need to be considered when thinking about screening?

Answer 8

• is it simple, safe, valid?
• is it acceptable to the public?
• have cut of levels been established?
• have the further investigations been established.

Question 9

Why does a screening program need to be simple and safe?

Answer 9

You’ll be conducting it on healthy individuals, it’s unfair to put them through extensive screening when there is nothing to be found.

Question 10

What are the 2 mistakes that can be made in screening?

Answer 10

• false positive (the patient has tested positive but do not have the disease)
• false negative (The patient has tested negative but actually does have the disease)

Question 11

What issues surround a false positive result?

Answer 11

a healthy individual will be turned into a patient and will undergo tests/examinations etc which they do not need.

A lot of unnecessary anxiety will be experienced.

unnecessary treatment.

oppertunistic costs (spending money on people who do not need it, when there are people who do need it who now cant use that money).

May be less likely to take up screening in the future

Question 12

What issues surround a false negative?

Answer 12

• you’re giving someone false reassurance

- may mean they present later than they would have which could lead to a worse prognosis down the line.

Question 13

What features of a screening test test it’s validity?

Answer 13

• sensitivity
• specificity
• positive predictive value (PPV)
• Negative predictive value (NPV)

Question 14

What is meant by sensitivity (Screening)?

Answer 14

How many people who have the disease test positive?

Also known as the detection rate.

         True positives ---------------------------------------------  true positives+false negatives.

Question 15

What is meant by specificity? (screening)

Answer 15

What is the probability that someone without the disease will test negatively?

           True negatives  ----------------------------------------------- true negatives + false positives.

Question 16

What is special about sensitivity and specificity? (Screening)

Answer 16

They are consistent.

The same test applied in the same way will get the same sensitivity and specificity.

Question 17

Do you want sensitivity and specificity to be high or low?

Answer 17

High

Question 18

What is a positive predictive value?

Answer 18

If i have tested positive, what is the chances of me actually having the disease?

true positive + false positive

Question 19

What is a negative predictive value?

Answer 19

if i have tested negative, what are the chances of me not having the disease?

true negative + false negative.

Question 20

What is the positive predictive value strongly affected by?

Answer 20

The prevalence of the disease.

will be lower in lower prevalence populations, may test positive but the chances of you having the disease are slim

Question 21

Do you want positive predictive values to be high or low?

Answer 21

from the view of the patient, you’d want it to be low, (if you’ve tested positive you want it to be unlikely that you actually have the disease)

From the view of screening, you want it to be high. You dont want to incorrectly test positive for people who dont have the disease, you want a lot of the people coming up positive to actually have it.

Question 22

What features do you want from an intervention if you’re considering screening?

Answer 22

• intervention must be known to increase outcomes.

- HCW should know what interventions take place when there is a positive result.

Question 23

What features about the screening programe need to be considered when thinking about screening?

Answer 23

• needs to have proven effectiveness at reducing mortality/morbidity.
• needs to be acceptible
• benefits to patients should outweight harms
• oppertunity costs must be balanced with medical expenditure.

Question 24

What factors surrounding implementation need to be considered when thinking about screening?

Answer 24

• there should be adequate staffing/facilities.
• there should be a monitoring program
• all other options for managing the condition should have been considered

Question 25

What are the main problems associated with screening?

Answer 25

• lead time bias
• length time bias
• selection bias
• public pressure to have other screening programs
• false results

Question 26

What is lead time bias?

Answer 26

Becuase of earlier detection, it looks as though people live longer, when in fact they just know about the disease for longer.
Make survival look better, when it isnt.

Question 27

What is length time bias?

Answer 27

Screening favours slow growing conditions rather than fast growing/aggressive conditions.

Detected conditions are more likely to have a favourable outcome anyway, may not have needed treatment.

Question 28

What is selection bias, with regards to screening?

Answer 28

the people who go to screening programs are more likely to do other things that promote good health too, such as eating well, adherance.

Question 29

Why do people need to be given an informed choice about screening?

Answer 29

-need to know about the risks of testing incorrectly, and what that could mean.

Question 30

What are some sociological critiques of screening?

Answer 30

• victim blaming- patient is responsible for going to screening etc, some aren’t able to.
• surveillance- to what extent can we invade people’s privacy to try to increase population health?
• feminist- more screening aimed at women, more faulty body, needs checking more
• Moral obligation- feel obliged to go, if you don’t want to it’s difficult to bring up with HCW, may feel judged, or be seen as ignorant despite it being you’re personal choice.