A Delphi consensus to advance on a Clinical Case Definition for Post COVID-19 condition: A WHO protocol

Background: While most people developing COVID-19 recover quickly and completely, a proportion of those infected with SARS-CoV-2 develop persistent symptoms, which can be disabling. After establishing the interim nomenclature for Post COVID-19 condition, there is a need to establish a clinical case definition to be used by all parties in all settings. Of the many definitions available to date, none is universal and the WHO has engaged in formally defining the Post COVID-19 condition based on existing evidence and by means of the most robust methodology. A key element for success is to engage patients and advocacy groups in this exercise.

The objective of the study "Delphi consensus to advance on a Clinical Case Definition for Post COVID-19 condition" is to determine the domains, variables and values (thresholds) for inclusion into a clinical case definition for Post COVID-19 condition, using a Delphi consensus methodology.

Methods: This study is a prospective, Delphi consensus-seeking exercise, mixed, iterative survey of internal and external experts, patients and other stakeholders. Panelists (individual participants who will fill the online survey in) will fulfil the criteria of balanced representativity of all WHO regions, age and gender balance, specialty diversity, and patients.

We aim to sample approximately 100 panelists for this Delphi task, and the COMET Initiative DelphiManager software will be used. DelphiManager is a web-based system designed to facilitate the building and management of Delphi surveys.

From an initial, comprehensive list of 14 domains identified, 10 have been selected, some of them with a number of sub-domains. It is envisaged that panelists will reach consensus after two Delphi rounds. The questionnaire with all agreed domains/variables will be followed by a series of questions relating to these variables with eventual values/thresholds (Appendix 2). Registration of panelists and the actual Delphi questionnaire are accessible via this link https://delphimanager.liv.ac.uk/DefiningPostCOVID/Delphi

'Consensus' will be obtained on a question if 70% or more of the responses fall within the same response on a 9-point Likert scale. 'Disagreement' will occur if 35% or more of responses fall in both of the two extreme ranges of possible options on the Likert scale. All other combinations of panel answers will be considered 'partial agreement'.

Discussion: Establishing a satisfactory clinical case definition of Post COVID-19 condition is needed to enable systematic investigations of the incidence, duration and pathogenesis of Post COVID-19 condition, and to eventually develop effective treatments and successful management strategies and care pathways. This working clinical case definition may change as new evidence emerges, data are pooled and our understanding of the consequences of COVID-19 develops further.