Clinical Assessment

A thorough clinical assessment is essential for ME/CFS diagnosis, both to establish the presence of diagnostic criteria and to rule out alternative explanations for symptoms.

1 History Taking

1.1 Onset Characterization

The pattern of disease onset provides diagnostic and prognostic information:

Sudden Onset (60–80% of cases):

  • Patient can identify exact date or event when illness began
  • Most commonly follows acute infection: infectious mononucleosis (EBV), influenza, COVID-19, gastroenteritis
  • May follow other physiological stressors: surgery, trauma, childbirth, vaccination
  • Strong temporal association suggests post-infectious mechanism
  • Diagnostic value: Sudden onset after documented infection strongly supports ME/CFS diagnosis

Gradual Onset (20–40% of cases):

  • Symptoms develop over weeks to months without clear precipitant
  • May follow period of chronic stress, cumulative sleep deprivation, or overwork
  • Patient cannot identify specific triggering event
  • Diagnostic challenge: Gradual onset requires more thorough differential diagnosis (autoimmune disease, occult malignancy, endocrine disorders)

1.2 Key Questions for Establishing Diagnosis

Post-Exertional Malaise Assessment:

  • “After physical activity, do you feel worse than expected?”
  • “Is there a delay between activity and symptom worsening? How long?” (Typical: 12–72 hours)
  • “How long does it take to recover from doing too much?” (ME/CFS: days to weeks)
  • “Can you reliably predict what activities will make you crash?”
  • “Do mental tasks (reading, concentration) also trigger symptom flares?” (Cognitive PEM distinguishes ME/CFS from deconditioning)

Sleep Assessment:

  • “Do you wake up feeling refreshed?” (ME/CFS: No, regardless of duration)
  • “How many hours do you sleep?” (Rule out insufficient sleep)
  • “Do you snore? Have you been told you stop breathing during sleep?” (Screen for obstructive sleep apnea)
  • “What time do you go to sleep and wake up?” (Assess circadian rhythm disorders)

Cognitive Dysfunction:

  • “Do you have trouble finding words or finishing sentences?”
  • “Do you lose your train of thought mid-conversation?”
  • “Can you read and retain information like you used to?”
  • “Do you have difficulty with tasks that require sustained focus?”
  • “Are these problems worse after physical or mental exertion?” (Cognitive PEM)

Orthostatic Symptoms:

  • “Do you feel dizzy or lightheaded when standing up?”
  • “Are showers or baths difficult? Do you need to sit?”
  • “Do your symptoms worsen when standing for extended periods?”
  • “Do you feel better when lying down?”

Functional Impact Assessment:

  • “What percentage of your pre-illness activity level can you sustain now?”
  • “What activities have you had to give up?” (Work, social activities, hobbies, childcare)
  • “On a scale of 0–100 (Bell Disability Scale), what is your functional capacity?”
  • “How many hours per week do you spend horizontal (lying down)?”

2 Physical Examination

2.1 Orthostatic Vital Signs

ImportantRequirement: NASA Lean Test or Orthostatic Vital Signs

Orthostatic intolerance assessment should be performed on all ME/CFS patients:

Protocol:

  • Patient supine for 5 minutes → measure heart rate (HR) and blood pressure (BP)
  • Patient stands upright → measure HR and BP at 1, 3, 5, and 10 minutes
  • Record symptoms during test (lightheadedness, nausea, cognitive impairment)

Abnormal Findings:

  • Postural Orthostatic Tachycardia Syndrome (POTS): HR increase \(\geq 30\) bpm (or \(\geq 40\) bpm in adolescents) within 10 minutes of standing, without orthostatic hypotension
  • Orthostatic Hypotension: Systolic BP decrease \(\geq 20\) mmHg or diastolic BP decrease \(\geq 10\) mmHg
  • Neurally Mediated Hypotension (NMH): Delayed BP drop (after 5–10 minutes standing)
  • Symptom reproduction: Patient reports typical symptoms even without meeting BP/HR criteria

Interpretation: 70–90% of ME/CFS patients demonstrate orthostatic intolerance on objective testing. Absence of objective findings does not exclude ME/CFS, but presence strongly supports the diagnosis and guides treatment (salt, fluids, fludrocortisone, midodrine).

2.2 Neurological Examination

The neurological examination in ME/CFS typically shows:

Usually Normal:

  • Cranial nerves intact
  • Motor strength 5/5 (though patients report subjective weakness)
  • Deep tendon reflexes normal
  • No pathological reflexes (Babinski negative)

Potential Abnormalities:

  • Cognitive testing: Impaired serial 7s, word recall, attention tasks
  • Tandem gait or Romberg: May reveal subtle ataxia or balance impairment
  • Sustained muscle testing: Rapid fatigability (e.g., handgrip dynamometer shows dramatic decline with repeated testing)
  • Sensory testing: Hyperalgesia or allodynia in some patients (small fiber neuropathy)

Clinical Significance: The paucity of objective findings on standard neurological examination despite severe symptoms is characteristic of ME/CFS. This discordance (severe functional impairment with normal gross exam) historically led to dismissal of ME/CFS as “psychosomatic,” but advanced imaging and functional testing reveal objective abnormalities (cerebral blood flow reduction, autonomic dysfunction, immune activation). ### Tender Point Assessment

30–70% of ME/CFS patients meet criteria for fibromyalgia (widespread pain with tender points). Assessment:

  • Digital palpation of 18 tender point sites with 4 kg pressure
  • Fibromyalgia: \(\geq 11\) of 18 sites tender
  • Presence of fibromyalgia does not exclude ME/CFS; these are frequently comorbid
  • Guides pain management strategy

3 Laboratory Testing

3.1 Mandatory Exclusionary Testing

ImportantRequirement: Minimum Laboratory Workup

The following tests are required to rule out alternative diagnoses:

Hematology:

  • Complete Blood Count (CBC): Rule out anemia, leukemia, lymphoma
  • If anemia present: Iron studies, B12, folate

Chemistry:

  • Comprehensive Metabolic Panel (CMP): Rule out renal failure, hepatic dysfunction, electrolyte disorders, diabetes

Endocrine:

  • Thyroid function: TSH, free T4 (hypothyroidism is a common mimic)
  • Consider: Morning cortisol, ACTH stimulation test if Addison disease suspected

Inflammation:

  • Erythrocyte Sedimentation Rate (ESR) or C-Reactive Protein (CRP): Rule out active inflammatory disease
  • Note: ESR/CRP are typically normal in ME/CFS, distinguishing it from autoimmune diseases

Autoimmune Screening:

  • Antinuclear Antibody (ANA): Screen for lupus, Sjögren syndrome, other connective tissue diseases
  • If ANA positive: Reflex to specific antibodies (anti-dsDNA, anti-Ro, anti-La)

Vitamins:

  • Vitamin D: Deficiency is extremely common and contributes to fatigue
  • Vitamin B12: Deficiency causes fatigue and cognitive impairment

Sleep Disorders:

  • Polysomnography: Rule out obstructive sleep apnea (OSA) or upper airway resistance syndrome (UARS)
  • OSA can fully mimic ME/CFS; CPAP treatment produces dramatic improvement in true OSA
  • OSA and ME/CFS can coexist; treating comorbid OSA improves but does not cure ME/CFS

The characteristic laboratory finding in ME/CFS is that standard tests are normal:

  • CBC: Normal (no anemia, normal WBC count)
  • CMP: Normal (normal kidney, liver, electrolytes)
  • TSH: Normal
  • ESR/CRP: Normal or low-normal (distinguishes from inflammatory autoimmune diseases)
  • ANA: Usually negative (or low-titer positive without clinical significance)

This pattern—severe functional disability with normal routine labs—is diagnostically significant. It distinguishes ME/CFS from conditions that present with obvious laboratory abnormalities. ### Advanced Biomarker Testing (If Available)

If resources permit, advanced testing can guide treatment:

Autoimmune Domain:

  • GPCR autoantibody panel (\(\beta_2\)-adrenergic, M3/M4 muscarinic)
  • NK cell count and cytotoxicity assay
  • Flow cytometry for plasma cell populations (CD38+CD138+)

Metabolic Domain:

  • Heng 7-biomarker panel (AMP, ADP, VWF, fibronectin, TSP-1, PDGF-BB, TGF-\(\beta\) 3) when commercially available
  • Fasting lactate (elevated suggests mitochondrial dysfunction)
  • ATP profile (specialized labs only)

Objective Functional Testing:

  • Two-day cardiopulmonary exercise testing (CPET): Gold standard for documenting PEM
  • Day 1 vs. Day 2 comparison shows failure to reproduce work capacity
  • Reduction in VO2max, ventilatory threshold on Day 2 is diagnostic

Autonomic Testing:

  • Formal tilt table testing (if orthostatic symptoms prominent)
  • Heart rate variability analysis
  • Quantitative sudomotor axon reflex test (QSART)

These tests are not required for diagnosis but enable Tier 2 biological phenotyping and treatment stratification.