A Comparison of Case Definitions for Myalgic Encephalomyelitis and Chronic Fatigue Syndrome.
Sunnquist, Madison, Jason, Leonard A, Nehrke, Pamela et al. · Journal of chronic diseases and management · 2017 · DOI
Quick Summary
This study compared two different sets of diagnostic criteria used to identify ME/CFS patients. Researchers found that 76% of people diagnosed with chronic fatigue syndrome met the newer Institute of Medicine criteria, but only 44% met the revised London criteria. The London criteria identified patients who were more severely physically impaired, suggesting that different diagnostic tools can identify different groups of patients.
Why It Matters
Different diagnostic criteria can identify very different groups of ME/CFS patients with varying symptom severity and functional impairment. Standardizing which criteria clinicians and researchers use is essential for ensuring consistent diagnosis, enabling researchers to find reliable biomarkers, developing effective treatments, and conducting studies that can be compared across different research groups.
Observed Findings
76% of the CFS-diagnosed sample met the Institute of Medicine criteria for ME
44% of the CFS-diagnosed sample met the revised London criteria for ME
The revised London criteria identified patients with greater physical impairment compared to those meeting only IOM criteria
Significant discordance exists between the two case definitions in patient identification
Inferred Conclusions
A standardized, operationalized case definition for ME is needed to reduce sample heterogeneity across research studies
The choice of diagnostic criteria substantially influences which patients are identified and the severity profile of identified populations
Future research using inconsistent case definitions may yield non-replicable findings and impede biomarker discovery and treatment development
The London criteria may identify a more severely affected subgroup within the broader CFS population
Remaining Questions
Which diagnostic criteria better predicts treatment response or disease progression?
How do these different criteria relate to underlying biological markers or pathophysiology?
What This Study Does Not Prove
This study does not prove which diagnostic criteria is 'correct' or optimal—it only demonstrates that different criteria identify different populations. It does not test whether either criterion can predict treatment response or identify underlying biological causes of ME/CFS. The study does not establish causation between specific symptoms and the level of impairment observed.