Development of the long COVID - 6 dimensions quality of life (LC-6D-QoL) scale: a Delphi study

Long COVID significantly impairs quality of life through multi-systemic complexity, including fatigue, cognitive dysfunction, and dysautonomia. Existing generic tools fail to capture these manifestations, limiting patient-centered assessment. To address this gap, this study proposed a patient-focused, 16-item scale developed and content-refined through expert consensus, to evaluate quality of life in people with Long COVID.

A two-round Delphi study involved two rounds of questionnaires and feedback. 37 experts with clinical or research experience in Long COVID participated in the first round, and 26 completed the second. In the first round, experts rated the relevance of proposed indicators. The second questionnaire incorporated modifications based on the experts' comments. Quantitative data were analyzed using descriptive statistics and agreement measures, while qualitative comments were thematically coded.

Experts reached substantial agreement, above 83%, on the dimensions covering the main aspects of quality of life. Based on participants' comments, the initial scale was modified, and a consensus between 80 and 92% was reached in all dimensions. The Delphi process resulted in a scale composed of 6 dimensions and 16 items, which include dysautonomia assessment and affective-sexual life impact, omitted in generic tools. The dimensions of the LC-6D-QoL Scale were: (1) general health; (2) physical health; (3) mental health; (4) daily functioning; (5) social relationships and support; and (6) economic and work-related aspects.

This study establishes an expert-informed foundation for future validation of the LC-6D-QoL Scale, integrating clinical and experiential knowledge to refine its preliminary structure. The LC-6D-QoL Scale is a patient-centered instrument capturing six key dimensions often missed in generic tools-such as dysautonomia, mental fatigue, and work-related impact-to better assess quality of life in Long COVID.