Long Covid Clinical Severity Types Based on Symptoms and Functional Disability: A Longitudinal Evaluation

Background: Long Covid (LC) is a multisystem clinical syndrome with Functional Disability (FD) and compromised Overall Health (OH). There is a lack of distinct clinical symptom clusters (phenotypes) identified in LC so far but there is emerging information on LC clinical severity types. This study explores the consistency of these clinical severity types over time and the relationship between Symptom Severity (SS), FD, and OH in the context of the clinical severity types in a prospective sample. Methods: A purposive sample of LC patients recruited to the LOng COvid Multidisciplinary consortium Optimising Treatments and servIces acrOss the NHS (LOCOMOTION) study were assessed using the modified COVID-19 Yorkshire Rehabilitation Scale (C19-YRSm) at two assessment time points. A cluster analysis for clinical severity types was undertaken at both time points using k-means partition using two, three, and four initial clusters and different starting values. Cluster analysis was also carried out to assess the presence of symptom phenotypes (symptom clusters). Findings: Cross-sectional data was available for 759 patients with 356 patients completing C19-YRSm at the two assessment points. Mean age was 46·8 years (SD = 12·7), 69·4% were females, and median duration of LC symptoms at first assessment was 360 days (IQR 217 to 703 days). Cluster analysis revealed three distinct SS and FD clinical severity types - mild (N=96), moderate (N=422), and severe (N=241) - with no distinct symptom phenotypes. The three-level clinical severity pattern remained consistent over time between the two assessments, with 51% of patients switching the clinical severity type between the assessments. The fluctuation was independent of the LC severity and time between the assessments. Interpretation: This is the first study in the literature to show the consistency of the three clinical severity types over time with patients also switching between severity types indicating the fluctuating nature of LC. Keywords: SARS CoV-2, Post-COVID-19 condition, Post-COVID-19 syndrome, C19-YRS, phenotypes