Conditions to test for before concluding Chronic Fatigue Syndrome

A reader in Australia has had CFS for 2 years. She wishes to exclude other treatable diseases that could mimic CFS (and potentially be treatable). The Research definition of CFS states that CFS should only be given as a diagnosis AFTER excluding other possibilities. This is unfortunately not always the case. “Any unexplained abnormality detected on examination or other testing that strongly suggests an exclusionary condition needs to be resolved before attempting further classification.”

[1994 CDC] Any past or current diagnosis of:

  • major depressive disorder with psychotic or melancholic features
  • bipolar affective disorders
  • schizophrenia of any subtype
  • delusional disorders of any subtype
  • dementias of any subtype
  • anorexia nervosa
  • or bulimia nervosa
  • Alcohol or other substance abuse, occurring within 2 years of the onset of chronic fatigue and any time afterwards.


  • untreated hypothyroidism,
  • sleep apnea,
  • narcolepsy, and
  • iatrogenic conditions such as side effects of medication.
  • Severe obesity is defined as having a body mass index equal to or greater than 45


  • diagnosable illnesses may relapse or may not have completely resolved during treatment.
    • hepatitis B or C virus infection
  • Brain Injury – Traumatic or by prior infection

Other items

  • Phosphate Diabetes: 10% of CFS patients had been misdiagnosed and had phosphate diabetes [1998]
  • Pfisteria

  • From British Medical Journal 2015
    • “Infectious mononucleosis antibody titer indicates past infection and fatigue could last a month or 2 at most.”
    • “post parvo virus B19 fatigue. This post viral syndrome is the easiest to spot as it always shows isolated low red cell count.”
  • Young-Onset Monogenetic Parkinsonism [2011]