Lead Time, Diagnosis and Treatment

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来自 University of Geneva 的课程

Disease Screening in Public Health

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University of Geneva

Disease Screening in Public Health

57 个评分

Current and future public health is characterized by the increase of chronic and degenerative diseases, corresponding to the worldwide ageing of the population. The increasing prevalence of these conditions together with the long incubation period of the chronic diseases and the continual technological innovations, offer new opportunities to develop strategies for early diagnosis. Public Health has an important mandate to critically assess the promises and the pitfalls of disease screening strategies. This MOOC will help you understand important concepts for screening programs that will be explored through a series of examples that are the most relevant to public health today. We will conclude with expert interviews that explore future topics that will be important for screening. By the end of this MOOC, students should have the competency needed to be involved in the scientific field of screening, and understand the public health perspective in screening programs. This MOOC has been designed by the University of Geneva and the University of Lausanne. This MOOC has been prepared under the auspices of the Ecole romande de santé publique (www.ersp.ch) by Prof. Fred Paccaud, MD, MSc, Head of the Institute of Social and Preventive Medicine in Lausanne (www.iumsp.ch), in collaboration with Professor Antoine Flahault, MD, PhD, head of the Institute of Global Health, Geneva (https://www.unige.ch/medecine/isg/en/) and Prof. Gillian Bartlett-Esquilant (McGill University, Quebec/ Institute of Social and Preventive Medicine, Lausanne).

从本节课中

Introduction to Key Concepts in Screening

This module will provide a brief welcome by Dr. Fred Paccaud and Dr. Antoine Flahault. An overview of screening and an introduction on how the course is organized and evaluated will be provided by Dr. Gillian Bartlett-Esquilant. Dr. Idris Guessous, a Senior Lecturer in the Population Epidemiology Unit in the Department of Community Medicine, Primary Care and Emergency Medicine (Geneva), and in the Department of Ambulatory Care and Community Medicine (PMU Lausanne) & Division of Chronic Diseases at the Institute of Social and Preventive Medicine (Lausanne) will provide lectures on definitions of screening. Natural history of diseases and the characteristics of subclinical conditions allowing early diagnosis will be presented. A quiz on the key concepts for screening will complete this module.

Definition of Screening4:30

Definition of a Screening Program4:06

Natural History of Diseases4:22

Lead Time, Diagnosis and Treatment5:04

Risk of Overdiagnosis4:19

Screening Tests and Biomarkers4:29

The Prevention Paradox6:34

Target Populations for Screening4:40

与讲师见面

Antoine Flahault
Professor of Public Health and Director of the Institute of Global Health (Faculty of Medicine, University of Geneva) and co-Director of Centre Virchow-Villermé (Université Paris Descartes)
University of Geneva and Université Paris Descartes – Sorbonne Paris Cité
Fred Paccaud (In Partnership with UNIGE)
Professor of epidemiology and public health and Director of the Institute of social and preventive medicine
Lausanne University Hospital
Gillian Bartlett-Esquilant
Professor of Epidemiology and Research and Graduate Program Director and Associate Chair for the Department of Family Medicine at McGill University.
University of Lausannne and McGill University

[MUSIC]

So, we have discussed the definition of screening.

We review what is the natural history of disease.

Now to understand really screening,

we have to put together prevention and the natural history

of disease that we just discussed and this is what we will review in this lesson.

The amount of time by which the diagnosis is early in screening is called lead time.

Lead time is necessary in screening.

You have to make a diagnosis earlier.

You have to treat the disease earlier.

You will often see lead time discussed as a bias,

something which is a systematic error,

but always remember that lead time is necessary.

Still, you have to avoid the lead time bias that will be

discussed in the module or lessons on bias in screening.

But lead time is really necessary, is fundamental in screening.

If you do not capture the disease earlier, if you do not have a treatment that

is more beneficial early than later, you do not have any reason to implement

screening whether at population level or or at an individual level.

Again, lead time is the time that diagnosis would have occurred if screening

had not been done.

This is what you have done earlier than usual care.

Sometime, it works.

Most of the time, you do not change the prognostic of

the disease by identifying earlier the disease.

We will discuss the reason why.

On this slide again, this concept will be discussed in other lessons.

But you have to remember that lead time will give

you the advantage of improving the prognostic.

And as you can see on this slide, this is only worth doing when you can really

have an impact on the mortality of the population.

So for example, on this slide, you have three situations.

Each are characterized by the natural history of disease that we discussed.

The first, molecular changes due to risk factor exposure.

Early diagnosis by screening.

Usual diagnosis, because of presence of signs or symptoms and death.

Let's take an example of the absence of screening.

The natural history would be that at some point in your life,

individual in the white circle will have signs,

symptoms and the diagnose will be post.

At a given time, this individual will die.

And ineffective screening will be the situation where you

use the test, screening test for early diagnosis.

And you can see here, the lead time,

the time you have won by using a screening test.

But as you can see by knowing earlier, even by treating earlier,

this individual in the black circle will die at the same moment or

same time as the individual in the absence of screening.

So for him or for the patient, for the participant, there is no gain.

Maybe he has known his disease for two, three,

four years before you would have known.

But maybe even taking advantage of it being more anxious,

being more concerned about this disease result having any benefits of it.

An effective treatment, this is the last scenario

is the individual in blue circle who has gain some time.

But the lead time and thanks to that lead time,

The earlier diagnosis, the earlier effective treatment.

As you can see, there's a real impact on his life or her life.

Because he would live longer as shown on this figure.

We will discuss in the next lesson the lead time,

how lead time can lead to a over diagnosis and how it is related.

[MUSIC]

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