Introduction to JLL Explanatory Essays

Format: Websites
Language/s: English
Short Description:

Professionals sometimes harm patients by using inadequately evaluated treatments. Research addressing uncertainties can reduce this harm.

Key Concepts addressed:


Despite acting with the best of intentions, health professionals have sometimes done more harm than good to the patients who have looked to them for help. Some of this suffering can be reduced by ensuring that fair tests are done to address uncertainties about the effects of treatments.

Over the past half century, health care has had a substantial impact on people’s chances of living longer and being free of serious health problems. It has been estimated that health care has been responsible for between a third and a half of the increase in life expectancy and an average of five additional years free of chronic health problems. Even so, the public could have obtained – and still could obtain – far better value for the very substantial resources its invests in research intended to improve health ( Furthermore, some of the treatment disasters of the past could have been prevented, and others could be prevented in future.

Misleading claims about the effects of treatments are common, so all of us should understand how valid claims about the effects of treatments are made. Without this knowledge, we risk concluding that useless treatments are helpful, or that helpful treatments are useless. The James Lind Library has been created to improve general understanding of fair tests of treatments in health care, and how these have evolved over time.

The Explanatory Essays in The James Lind Library have been written to promote wider understanding of why fair tests of treatments are needed, and what they have come to consist of. You can access each essay by clicking on the relevant links below; or, if you want to download all of the essays so that they can be printed out together for reading off screen, click here.

James Lind Library

This is a James Lind Library Explanatory Essay

The text in these essays may be copied and used for non-commercial purposes on condition that explicit acknowledgement is made to The James Lind Library (

Fair tests of treatments

1.0 Introduction to JLL Explanatory Essays (this page)

1.1 Why treatment uncertainties should be addressed

1.2 Why treatment comparisons are essential

1.3 Why treatment comparisons must be fair


2.0 Avoiding biased treatment comparisons

2.1 Why comparisons must address genuine uncertainties

2.2 The need to compare like-with-like in treatment comparisons

2.3 Why avoiding differences between treatments allocated and treatments received is important

2.4 The need to avoid differences in the way treatment outcomes are assessed

2.5 Bias introduced after looking at study results

2.6 Reducing biases in judging unanticipated possible treatment effects

2.7 Dealing with biased reporting of the available evidence

2.8 Avoiding biased selection from the available evidence

2.9 Recognizing researcher/sponsor biases and fraud

The play of chance

3.0 Taking account of the play of chance

3.1 Recording and interpreting numbers in testing treatments

3.2 Quantifying uncertainty in treatment comparisons

3.3 Reducing the play of chance using meta-analysis

Bringing it all together for the benefit of patients and the public

4.0 Bringing it all together for the benefit of patients and the public

4.1 Improving reports of research

4.2 Preparing and maintaining systematic reviews of all the relevant evidence

4.3 Using the results of up-to-date systematic reviews of research