With myalgic encephalitis, the ESR will be:

• A. Increased
• B. Decreased (0-3)
• C. Normal
• D. Highly variable

Answer: (B)

In ME/CFS there isn’t an active systemic inflammatory process driving the illness. Erythrocyte sedimentation rate (ESR) is a nonspecific marker of inflammation, so it is not expected to be elevated in this condition. A very low ESR, such as 0–3 mm/hour, is consistent with the absence of inflammation and aligns with the idea that ME/CFS does not show inflammatory activity on this marker.

That helps explain why an increased ESR would be unlikely in ME/CFS (it would point toward an inflammatory or infectious process), and why ESR can be normal in many cases as well. The key point is that ME/CFS is not characterized by elevated inflammatory markers, so a low or normal ESR fits with the non-inflammatory nature of the syndrome.