Screening 101 – lesson plans

“Screening saves lives” – trips off the tongue doesn’t it

Try this – “Screening does harm, sometimes good, often huge opportunity cost” – trickier to land on a daily mail headline?

And this -“screening rarely does more good than harm in the context of a programme that is both clinically and cost effective, and affordable.” …..mouthful?

Tricky isn’t it.

So often, we hear that screening is a marvel. Sometimes it is, often it isn’t.

There are a number of important concepts underpinning screening that we could do with not forgetting.

I’m not writing the screening 101 in full here, but merely a lesson plan. I’m not especially an expert. I have, however been to “screening 101”, and 102 & 103 etc. And I’ve been lucky enough to have been taught screening by some of the best in the business.

Pay attention. There will be a test. Lesson plan follows.

1. Read Raffle / Gray – the bible, never bettered

2. Screening is NOT “the test”, it is the programme in totality

3. Screening = case finding = screening. The end. Hetes why.

4. QA of screening programme is essential, no critical

5. All proposals to screen must properly satisfy the Wilson Jungner criteria. Look it up. Modified WJ in operation in UK, overseen by NSC

6. of course there are judgements to be made and trade offs in context of not full satisfaction of WJ criteria, these judgements should be make by people who have been to screening 101 class. In the uk that group of people are called the “National Screening Committee”.

7. Pay particular attention in ethics class – invite people who believe they are a well for a test the downstream consequences of which might do that person good, but may also do them harm. Screening is indeed special. See hereOne of the key ethical principles (justice) means “Screening programmes should be used only when all other primary preventive measures are in place (because primary prevention is likely to be more cost-effective than screening)”

8. Pay particular attention in the classes on lead time bias and length bias. These are tricky little concepts but important. Some initial insights here.

9. Try to think about the value foregone in the opportunity cost of time spent screening. What might the staff involved in screening alternatively do with their time, that has value. It’s rather hard to capture. Some thoughts here.

10. It NSC has sad no, doesn’t mean you can reframe it as case finding. Here’s why. If NSC hasn’t said anything, it doesn’t mean you know best and start screening populations for it

That’s enough for lesson 1

Dosing instructions



Read regularly

Repeat till it sinks in.

Other refs

Diabetes screening – doesn’t pass NSC test but still done at scale. Issue here

Good primer here

series of excellent twitter threads on some of the important concepts underpinning this here, here and here


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