Core outcome measurement instruments for use in clinical and research settings for adults with post-COVID-19 condition: an international Delphi consensus study

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has placed a significant burden on public health worldwide. As of end of March 2021, there have been an estimated 125 million cases of coronavirus disease 2019 (COVID-19) globally. The acute presentation of COVID-19 has now been widely investigated and risk factors for in-hospital mortality identified.

It has now become evident that a significant portion of those with COVID-19 subsequently experience lasting symptoms including fatigue, breathlessness and neurological complaints months after the acute infection. This is now commonly referred to as Long COVID but has also been described as post-COVID syndrome or COVID long-haulers. Recently published the UK National Institute for Health and Clinical Excellence (NICE) COVID-19 guideline call infection sequalae “Post-COVID-19 syndrome”, defining it as “signs and symptoms that develop during or after an infection consistent with COVID-19, continue for more than 12 weeks and are not explained by an alternative diagnosis”. Interim definitions for the COVID-19 sequelae are, however, based on limited evidence from small cohorts with short-term follow-up. The World Health Organization at a recent global forum called countries to prioritise rehabilitation for the consequences of COVID-19, collect harmonised information on Long Covid and proposed the term “Post-Covid condition”.

There is an urgent need to optimise and standardise outcome measures for this important and emerging patient group both for clinical services and for research, especially clinical trials, to allow comparing and pooling of data. The aim of this project is to rapidly define a core outcome set (COS) for Post-Covid condition/Long Covid for both clinical (from low to high resource settings) and research use.


Sarah L Gorst, Nina Seylanova, Susanna R Dodd, Nicola L Harman, Margaret O’Hara, Caroline B Terwee, Paula R Williamson, Dale M Needham, Daniel Munblit, Timothy R Nicholson, and the PC-COS study group


Journal: Lancet Respir Med
Pages: -
Year: 2023
DOI: 10.1016/ S2213-2600(23)00370-3

Further Study Information

Current Stage: Completed
Date: March 2021 - September 2022
Funding source(s): NIHR

Health Area

Disease Category: Infectious disease

Disease Name: Coronavirus, Post-Covid condition

Target Population

Age Range: 18 - 120

Sex: Either

Nature of Intervention: Any

Stakeholders Involved

- Clinical experts
- Consumers (caregivers)
- Consumers (patients)
- Families
- Governmental agencies
- Journal editors
- Methodologists
- Patient/ support group representatives
- Researchers
- Service providers
- Service users
- Statisticians
- Epidemiologists

Study Type

- COS for clinical trials or clinical research
- COS for practice
- Recommendations for outcome measures (measurement/how)


- Consensus meeting
- Delphi process
- Focus group(s)
- Literature review
- Semi structured discussion
- Survey
- Systematic review

- Development of a long list of outcomes based on the data from ongoing ISARIC Long Covid living systematic review.

- Develop a survey for further translation into multiple languages which will be subsequently delivered in a single round to all relevant stakeholders.

- Separate surveys for (a) adults and (b) parents/carers and children are planned.

- Tiers of COS may be considered (e.g. Tier 1 – general and Tier 2 subspecialised to assess system-specific consequences of COVID-19).

- Existing COS initiatives will be reviewed for potential applicability for use in post-covid condition.

- Consensus meeting.

Listen to the podcast about the ‘how’ stage here: