Purpose: to develop an international validated patient-reported outcome measure for COVID-19 patients according to international guidelines.

In this phase III of the project, the preliminary questionnaire of 80 items will be tested. It has been developed based on literature review and interviews with health care professionals and patients (phase I-II).

In Phase III A patients will fill in the questionnaire followed by interviews on relevance, importance and wording of the questionnaire In Phase III B patients will fill in the questionnaire and an debriefing questionnaire. We will do explorative psychometric analyses.

This project aim to develop an international validated patient-reported outcome measure for COVID-19 patients according to international guidelines. The Phase I and II of this development process have been finalized. Based on a systematic literature review , interviews with 44 health-care professionals and 52 patients in 6-7 countries a final list of 80 questions, the preliminary Oslo COVID-19 QLQ - PW80 ©, is ready to be tested in the current Phase III of the development process.

The objectives of the phase III are:

• In a limited patient group, to check that the items make sense to the target population, that the phrasing and sequence of questions is acceptable, that there are no missing issues and that none of the questions are confusing and/or offensive (Phase IIIA).
• In addition, in a larger patient group, to test hypothesized subscales for psychometric properties including reliability, prevalence and variance (e.g. Cronbach's alpha coefficient and correlation-based methods) (Phase IIIB).

The end-product, the international COVID-19- specific questionnaire, will be a psychometrically robust patient-reported outcome measure (PROM) to assess HRQoL in patients with or after COVID-19 disease

Inclusion Criteria:

• Patients with verified SARS-CoV-2 infection (positive test according to local/national standards)
• Patients with active or previous symptomatic COVID-19 disease
• In-patients in hospitals and nursing homes or out-patients in hospitals or patients discharged from institutions to their home/covid-19 centres or patients staying at home/covid-19 centres during the course of the disease
• Patients aged 18 years and older
• Ability to read and comprehend the process and study documents as judged by the investigator
• Written informed consent

Exclusion Criteria:

• Patients in intensive care units (can be recruited after they have been dismissed)
• Inability to read and comprehend the process and study documents as judged by the investigator

To ensure content validity of the final questionnaire, the participants will be recruited according to specified recruitment matrices based on countries, language groups, age, gender, hospitalisation status, disease status and comorbidity.