What is OI? An umbrella term for symptoms that worsen when standing and improve when lying down. It’s a hallmark feature of ME/CFS, Long COVID, and other infection-associated chronic conditions (IACCs).
Why test? Most patients go undiagnosed too long. Testing confirms symptoms are upright-related and guides treatment, further testing, or specialist referral.
Three Common Tests
- Tilt Table Test (TTT): The “gold standard.” Comprehensive, closely supervised, useful for complex cases and research, but limited access and not always necessary for initial care.
- Active Stand Test (10-min): Simple, widely used by autonomic specialists, feasible in most clinics; may be hard for highly symptomatic patients.
- 10-Minute NASA Lean Test (passive): Practical for primary care, used by ME/CFS clinicians since the 1990s, safer and more comfortable for frail or very symptomatic patients due to wall support.
What Tests Can Do: Document abnormal HR/BP responses, confirm OI, guide initial treatment.
What They Can’t Do: Definitively diagnose autonomic disorders alone — diagnosis requires applying full clinical criteria (e.g., POTS = sustained HR rise ≥30 bpm, ≥40 bpm in adolescents, plus symptoms).
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