Evidence browser

ICD-10 Diagnoses prior to ME/CFS diagnosis in children and young people suggest potential early diagnostic indicators.

Wirth, Marielle, Haastert, Burkhard, Linnenkamp, Ute et al.·Scientific reports·2026

This study looked at medical records of young people (ages 6-27) diagnosed with ME/CFS to see what health problems they had in the year before their diagnosis. Researchers found that certain conditions—like fatigue, depression, pain disorders, and post-COVID-19 condition—appeared more often in people who later developed ME/CFS compared to similar young people who didn't develop it. This suggests these earlier diagnoses might be early warning signs or related to ME/CFS development, though the study cannot prove they actually caused ME/CFS.

E2 ModerateCohortPEM unclearObservational

Prediction of post-COVID chronic fatigue syndrome using data mining and machine learning techniques in Isfahan COVID cohort study.

Nematbakhsh, Shayan, Mohammadifard, Noushin, Riahi, Roya et al.·Journal of infection and public health·2026

Researchers used machine learning to identify factors associated with post-COVID fatigue in a cohort of 3,850 patients in Isfahan, Iran. The analysis identified 37 factors linked to fatigue; anxiety, BMI, depression, irritability, and memory issues were among the strongest predictors. A machine learning model achieved 85% accuracy at identifying patients at risk, though these results are based on observed associations and have not yet been validated in independent populations.

BiomarkersDiagnosticsImmune SystemLong COVID Overlap

Comprehensive Immunophenotyping of Monocytes and Dendritic Cells Suggests Distinct Pathophysiology in Chronic Fatigue Syndrome and Long COVID.

Petrov, Steliyan, Bozhkova, Martina, Ivanovska, Mariya et al.·International journal of molecular sciences·2026

Researchers compared immune cell patterns in 103 people with ME/CFS, 63 with long COVID, and 41 healthy controls using blood tests. They observed that ME/CFS and long COVID show different patterns of immune cell activity—long COVID appeared to show persistent immune activation, while ME/CFS appeared associated with reduced immune signalling. These are early findings from one study and do not yet tell us what causes either condition or how to treat it.

BiomarkersDiagnosticsCognitive Impairment

3D Virtual Reality Performance Metrics as a Future Fatigue Biomarker in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS).

Ladek, Anja-Maria, Priebe, Leonie, Harrer, Thomas et al.·Biomedicines·2026

Researchers tested how quickly 60 ME/CFS patients and 60 healthy controls could react to visual tasks presented in 3D virtual reality. ME/CFS patients showed slower reaction times across all difficulty levels, and they improved less with practice than controls did. The study reports an association between ME/CFS and prolonged reaction times, though the findings are preliminary and whether this could become a reliable test for fatigue severity requires further validation.

E2 ModerateCohortPEM not requiredCross-Sectional

Symptom profiles and health-related quality of life in Korean adults with post-acute sequelae of SARS-CoV-2 infection (PASC): A latent profile analysis.

Kim, Su-Jin, Kim, Jinhee·PloS one·2026

This study examined symptom patterns in 629 Korean adults with long COVID (persistent symptoms ≥12 weeks after COVID-19). Researchers identified four distinct groups: people with few symptoms, moderate multi-body symptoms, fatigue and post-exertional malaise-dominant symptoms, and severe multi-body symptoms. Quality of life decreased substantially as symptom burden increased. The findings are observational and reflect one population; whether they apply to ME/CFS remains unclear.

DiagnosticsCognitive ImpairmentPost-Exertional Malaise

E2 ModerateCohortPEM unclearObservational

Cardiopulmonary exercise test results do not change over two sequential days in patients with chronic fatigue syndrome.

Mancini, Donna M, Cook, Dane B, Brunjes, Danielle L et al.·Frontiers in physiology·2026

Researchers asked whether doing two exercise tests on consecutive days could reliably detect post-exertional malaise (PEM) in ME/CFS patients. They found that oxygen consumption and other key exercise measures did not change between Day 1 and Day 2 in either ME/CFS patients or healthy controls. However, ME/CFS patients reported much greater fatigue during exercise and had lower maximum heart rates. One study's findings do not establish whether this two-day test method is truly useful for measuring PEM in clinical practice.

DiagnosticsPost-Exertional Malaise

E2 ModerateDiagnosticPEM unclearCross-Sectional

Phosphoproteomic analysis reveals differential associations between liver-spleen disharmony and qi-blood deficiency syndromes in chronic fatigue syndrome.

Zhang, Jiabao, Tian, Ying, Sun, Guanghan et al.·Journal of translational medicine·2026

Researchers compared blood protein markers in 30 people—10 with ME/CFS showing Traditional Chinese Medicine (TCM) 'Liver-Spleen Disharmony' patterns, 10 with 'Qi-Blood Deficiency' patterns, and 10 healthy controls—using advanced protein analysis. They observed different patterns of phosphorylated proteins (chemical modifications on proteins) between the two ME/CFS groups and healthy controls, suggesting that TCM pattern categories may have distinct molecular signatures. However, this is an early exploratory study with a small sample size, and these findings have not yet been replicated.

BiomarkersDiagnostics

Improving myalgic encephalomyelitis population sampling: Applying an online respondent-driven method to address biases in G93.3 register data.

Kielland, Anne, Liu, Jing, Tyldum, Guri et al.·Journal of health psychology·2026

This study looked at how well official medical records capture ME/CFS cases and who gets diagnosed. Researchers found that medical register data misses many cases and disproportionately underrepresents people from lower-income backgrounds. They used a new online method to find ME/CFS patients more accurately and checked whether official diagnoses matched recognized diagnostic criteria.

Sleep in myalgic encephalomyelitis/chronic fatigue syndrome shows marked night-to-night fluctuation under free-living conditions-results from a matched case-control study.

Saurel, Maïtena, Fornasieri, Isabelle, Del Sordo, Giovanna C et al.·Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine·2026

This study observed that people with ME/CFS who wore sleep-tracking wristbands for a week showed poorer sleep quality and more night-to-night variability in how well they slept compared to matched controls—even though they spent more time in bed. The sleep pattern was unstable from night to night, which may be an important feature of ME/CFS sleep problems that laboratory studies (typically 1–2 nights) do not capture.

SleepDiagnostics

DiagnosticsPost-Exertional Malaise

Interpreting hand grip strength in hospital employees with post-COVID syndrome compared to non-infected controls: a case-control study.

Tack, Matthias, Gruber, Rosalie, Betting, Leia et al.·Scientific reports·2026

This small study compared hand grip strength in 19 hospital workers with post-COVID syndrome (including 7 who met ME/CFS criteria) to 23 healthy controls. Researchers found that grip strength tended to be lower in the post-COVID group, particularly when tested a second time after a 60-minute break, which might suggest difficulty recovering after repeated effort. However, these are preliminary findings from a small group, and the authors note that grip strength alone is not reliable enough to diagnose post-COVID syndrome.

E2 ModeratePEM unclearRegistry-Resource

Risk factors for severe post-COVID condition in children, adolescents, and young adults.

Donath, Quirin, Haegele, Matthias, Schindler, Daniela et al.·European journal of pediatrics·2026

This observational study from a German pediatric hospital followed 120 children and young adults with post-COVID condition (PCC), observing that those with more severe illness were more likely to have had 12 or more symptoms during their initial COVID-19 infection, alongside other acute symptoms such as trouble concentrating and fainting-like episodes. One quarter of participants met criteria for ME/CFS, and all of these were in the severely affected group; by analogy, if similar patterns apply to ME/CFS patients, early identification of high-symptom-burden acute illness might help predict who develops severe long-term illness. These findings are preliminary and come from a single hospital site.

Severe MEAutonomic Nervous SystemDiagnosticsCognitive Impairment

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome diagnostic reporting in the 2021-2023 National Health Interview Survey.

Fleig, Katherine, Nahin, Richard, Stussman, Barbara et al.·BMC public health·2026

A survey of over 86,000 US adults found that approximately 1.5% reported ever receiving an ME/CFS diagnosis. Among those, about 21% reported they no longer have the condition (Past ME/CFS), though roughly 40–50% of this group still experience symptoms and functional limitations similar to those currently diagnosed. This study observed that people who report having recovered from ME/CFS remain more impaired than those who never had the diagnosis, suggesting that reported recovery does not necessarily mean full symptom resolution.

E2 ModerateCohortPEM unclearLongitudinal

Two-timepoint multidomain follow-up of post-COVID condition and ME/CFS: overlapping autonomic, small-fiber, and cognitive changes.

Azcue, N, Barranco, C, Tijero-Merino, B et al.·Journal of translational medicine·2026

Researchers compared 21 people with post-COVID condition and 17 people with ME/CFS over about 2.5 years, measuring nerve function, autonomic symptoms, and cognitive performance. They observed that both groups showed similar patterns of changes over time—including worsening processing speed and cold sensation sensitivity, but improving heat sensation thresholds and verbal memory. While the two conditions appeared increasingly alike on follow-up testing, the study does not establish whether they are truly the same disease or simply share overlapping symptoms.

Pain and SensitizationAutonomic Nervous SystemDiagnosticsCognitive Impairment

BiomarkersDiagnosticsPost-Exertional Malaise

Raman Spectroscopy Combined with Machine Learning Reveals Myalgic Encephalomyelitis-Associated Biomolecular Signatures at Rest and After Standardized Stress.

Heidarifard, Maryam, Moezzi, Atefeh, Dallaire, Frédérick et al.·International journal of molecular sciences·2026

Researchers used a laboratory technique called Raman spectroscopy combined with computer learning to identify chemical signatures in blood plasma that are associated with ME/CFS. They collected blood samples from 115 ME/CFS patients and 45 healthy controls both at rest and 90 minutes after a standardized stress test, and found the method could distinguish between the two groups with moderate-to-good accuracy (79–84%). However, this is an early-stage study and much more work is needed before such a test could be used in clinical practice.

Differences in diagnostic coding in long COVID: sociodemographic and symptom interference factors.

Vickers, Jasmine K, Levitan, Emily B, Howell, Carrie R et al.·BMC infectious diseases·2026

Researchers surveyed 205 people with Long COVID to understand how severe symptoms interfere with daily life and whether their condition was formally recorded in medical records. They found that people reporting high symptom interference were more likely to be older, female, obese, or in poor general health—but among those with severe symptoms, having an official Long COVID diagnosis code in their medical record was not associated with these demographic factors. The study observed discrepancies between what patients reported and what appeared in their medical records, though researchers did not find evidence that doctors were coding the diagnosis based on demographic bias.

Severe MEDiagnosticsLong COVID OverlapPost-Exertional Malaise

Cardiopulmonary Exercise Testing Reveals Functional Limitations and Work Disability in Severe Post-COVID-19 and ME/CFS Patients.

Tomaskovic, Aleksandar, Weber, Vincent, Ochmann, David T et al.·Sports medicine - open·2026

A cross-sectional study of 92 severely ill post-COVID patients found that those meeting ME/CFS criteria had lower measured aerobic capacity (oxygen uptake and power output) on exercise testing compared to post-COVID patients without ME/CFS. Two-thirds of all patients showed objective signs of work disability on testing, and these measurements correlated with patients' own reports of disability and their employment status. The relevance of these findings specifically to ME/CFS requires caution, as the study enrolled primarily post-COVID patients, and the overlap between these conditions remains incompletely understood.

E2 ModeratePEM unclearBiobank-Resource

Defining a High-Quality Myalgic Encephalomyelitis/Chronic Fatigue Syndrome cohort in UK Biobank.

Samms, Gemma L, Ponting, Chris P·NIHR open research·2025

This study looked at how ME/CFS is identified in UK Biobank, a large database of health information from hundreds of thousands of people. Researchers found that about 1 in 100 UK Biobank participants had some evidence of ME/CFS, but only about one-third had strong, consistent evidence across multiple records. When they accounted for people too ill to participate in the study, they estimated that around 410,000 people in the UK have ME/CFS.

E2 ModerateCohortPEM not requiredCross-Sectional

The Diagnostic Journey of Dysautonomia Patients: Insights from a Patient-Reported Outcome Study.

O'Dell, John A, Walker, Ash, Latham, Andrew J et al.·Journal of patient experience·2025

This study followed 672 adults with dysautonomia (a condition where the nervous system that controls automatic body functions doesn't work properly) to understand how long it takes to get diagnosed and which doctors help with diagnosis. On average, it took 7.7 years for people to receive a diagnosis, and they often saw multiple types of doctors before getting answers. The study found that dysautonomia commonly occurs alongside other conditions like Ehlers-Danlos syndrome, mast cell disorders, and ME/CFS, which can make diagnosis even more confusing.

Autonomic Nervous SystemDiagnostics

E2 ModerateCohortPEM unclearRegistry-Resource

Unequal access to diagnosis of myalgic encephalomyelitis in England.

Samms, Gemma Louise, Ponting, Chris P·BMC public health·2025

This study examined NHS records from England to understand how many people have ME/CFS and whether diagnosis is fair across different groups. Researchers found that about 100,000 people in England have been officially diagnosed with ME/CFS, but the actual number may be much higher—around 404,000 in the UK. The diagnosis rates varied significantly depending on gender, age, ethnicity, and where people live, suggesting some patients are being missed.