A pilot cross-sectional investigation of symptom clusters and associations with patient-reported outcomes in [ME/CFS] and [PCC], 2024, Weigel et al

Background
Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is associated with long-term disability and poor quality of life (QoL). Cardinal ME/CFS symptoms (including post-exertional malaise, cognitive dysfunction and sleep disturbances) have been observed in Post COVID-19 Condition (PCC). To gain further insight into the potential role of ME/CFS as a post-COVID-19 sequela, this study investigates associations between symptoms and patient-reported outcomes, as well as symptom clusters.

Methods
Participants included Australian residents aged between 18 and 65 years formally diagnosed with ME/CFS fulfilling the Canadian or International Consensus Criteria or PCC meeting the World Health Organization case definition. Validated, self-administered questionnaires collected participants’ sociodemographic and illness characteristics, symptoms, QoL and functional capacity. Associations between symptoms and patient-reported outcomes were investigated with multivariate linear regression models. Hierarchical cluster analysis was performed to identify symptom clusters.

Results
Most people with ME/CFS (pwME/CFS) and people with PCC (pwPCC) were female (n = 48/60, 80.0% and n = 19/30, 63.3%, respectively; p = 0.12). PwME/CFS were significantly younger (x̄=41.75, s = 12.91 years) than pwPCC (x̄=48.13, s =10.05 years; p =0.017). Autonomic symptoms (notably dyspnoea) were associated with poorer scores in most patient-reported outcome domains for both cohorts. None of the four symptom clusters identified were unique to ME/CFS or PCC. Clusters were largely delineated by the presence of gastrointestinal and neurosensory symptoms, illness duration, ME/CFS criteria met and total symptoms.

Conclusions
Illness duration may explain differences in symptom burden between pwME/CFS and pwPCC. PCC diagnostic criteria must be refined to distinguish pwPCC at risk of long-term ME/CFS-like illness and subsequently deliver necessary care and support.

Plain English summary
Post COVID-19 Condition (PCC), or Long COVID, refers to the ongoing symptoms experienced after acute COVID-19 illness. The symptoms reported by people with PCC (pwPCC) resemble Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). However, existing diagnostic criteria for PCC are broad and cannot discern PCC subtypes (such as pwPCC experiencing ME/CFS-like illness), which may require different approaches to care. This study contributes to improving PCC case criteria and approaches to care for both ME/CFS and PCC by investigating the relationships between symptoms and patient-reported outcomes among pwPCC and people with ME/CFS (pwME/CFS).

For both cohorts, symptoms had a negative relationship with all aspects of health. Autonomic symptoms, notably breathing issues, returned the most negative associations. Pain, flu-like symptoms and lack of temperature control appeared more burdensome among pwPCC. These symptoms may signify the early stages of ME/CFS. Symptom clusters were also identified for the first time among a combined cohort of pwME/CFS and pwPCC in this study. Importantly, none of the symptom clusters were specific to ME/CFS or PCC. Instead, symptom clusters were defined by the prevalence of gastrointestinal and neurosensory symptoms, illness duration, ME/CFS criteria met and the total number of symptoms.

This study suggests that the few differences between ME/CFS and PCC may be explained by illness duration. These findings further implicate ME/CFS as a potential post-COVID-19 outcome. As ME/CFS is associated with profound reductions in quality of life and functioning, identifying pwPCC experiencing ME/CFS-like illness through refined diagnostic criteria must be prioritised to ensure the delivery of necessary care.

Link | PDF (Quality of Life Research, October 2024, open access)