CPRD_COPD Hawthorne Effect Study in Salford


CHESS: CPRD_COPD Hawthorne Effect Study in Salford: A UK cohort study to characterise patients enrolled in the Salford Lung Study and to evaluate a potential Hawthorne effect

Disease Areas Impacted

Chronic Obstructive Pulmonary Disease (COPD)

Project Overview

The Salford Lung Study is a pragmatic randomised controlled trial (pRCT) to test the effectiveness of a novel medicine compared with standard of care among patients with Chronic Obstructive Pulmonary Disease (COPD).  A pragmatic trial tests the effectiveness of the drugs in everyday clinical practice, as opposed to under strict clinical trial conditions. It is the first ever pre authorisation pragmatic randomised controlled trial. However, people often act differently when they are aware of being under surveillance (this applies to both patients and clinicians) – known as the Hawthorne Effect. The aim of this study is to compare the patients in the standard of care arm of the Salford Lung Study with other COPD patients in primary care. We can then advise as to whether the results from the trial are indeed applicable to everyday clinical practice.

Data Source

We are using a combination of an observational cohort of COPD patients from the Clinical Practice Research Datalink (CPRD) linked with Hospital Episode Statistics (HES) and Office for National Statistics (ONS) data, and trial data from the control arm of the Salford Lung Study (SLS).


We are comparing baseline characteristics (age, social economic status, co-morbidities, etc) of the SLS control arm with the CPRD cohort to place the members of the SLS in a wider context. We are then creating models that compare the rate of COPD exacerbations in the two groups to see if the rates of COPD exacerbation in the SLS are unusual. We will be considering the natural variation in the CPRD cohort which includes patients from all over the UK and assessing whether the SLS patients fit within this.


It is rare for the effectiveness of drugs in routine clinical practice to be known pre (or even post) authorisation. The SLS aims to uncover exactly this. It is therefore important to assess this key aspect of the design to provide more evidence to clinicians who will potentially be prescribing the drugs, ultimately leading to better care for COPD patients.


The outcome will be to assess whether there is a presence of the Hawthorne effect. Our findings will be presented alongside the trial results to aid their interpretation. If the results from the SLS are positive, it is important for doctors and clinicians to know to what extent these results are generalizable to routine practice, i.e. the conditions in which they will be prescribing the drug.

Findings and Publications

We have only just received the data and are currently cleaning it so there are no findings to report.



Researchers Involved

Dr Matthew Sperrin, Prof Tjeerd Van Staa, Alexander Pate, Michael Barrowman

Additional Information

The study is registered as an EU-PAS study and holds the ENCePP study seal. This represents external recognition of high standards throughout the research process – see