System Performance Assessment
Functional diagnostics
Functional diagnostics measure how the body's systems perform, at rest and under load. St. George Hospital runs heart rate variability, bio-impedance, mitochondrial, hormonal and metabolic tests in the first days of your stay, and the results decide the plan.
What is functional diagnostics?
Functional diagnostics assess how well the body's systems work. Together with laboratory tests and imaging they make up the hospital's diagnostics, and they are the measuring tool of our functional medicine work-up.
A conventional panel is built to find structural abnormalities or values beyond a threshold, which works well in acute disease. It helps less when your results are normal and your symptoms persist: fatigue that does not lift with sleep, recovery that takes days, brain fog, weight that changes without reason. Functional testing looks at how your metabolic, hormonal, immune and autonomic systems respond to load.
We use these tests to find the imbalance behind a symptom, then repeat them after treatment to check whether the plan worked.
The test categories and what each one answers
Your physician selects the tests from your history and earlier results. These are the ones we run most often.
| Test | What it measures | The question it answers |
|---|---|---|
| Heart rate variability (HRV) analysis | Beat-to-beat variation of the heart rhythm at rest and under a standing or breathing load | How well the autonomic nervous system regulates and recovers; whether the body is stuck in a stress state |
| Bio-impedance analysis | Body composition (fat, lean mass, water distribution) and the phase angle as a marker of cell membrane integrity | Whether muscle and cell mass have been lost, and how nutrition and infusions should be planned |
| Mitochondrial function testing | Markers of cellular energy production and the capacity of the mitochondria to respond to demand | Whether fatigue has a cellular energy component, and whether IHHT or infusion therapy should come first |
| Hormone profiling | Thyroid, adrenal, sex and growth hormones, including the diurnal cortisol pattern from samples across the day | Whether a hormone axis is depleted or out of rhythm, and whether that explains the symptoms |
| Metabolic panels | Nutrient utilization, oxidative stress markers and detoxification capacity | Whether the body can use what it is given, and how much oxidative load it carries |
Results are read against your symptoms as well as population ranges. The functional medicine testing guide explains the individual markers, and the magnesium article shows why an intracellular measurement can differ from the serum value.
How the testing runs on our ward
- Blood and urine are collected fasting on the first morning. For the cortisol rhythm, saliva or blood samples are taken at set times across the day.
- The HRV recording takes about 20 minutes, lying and standing, with electrodes on the chest. You breathe normally; a paced-breathing segment may be added.
- Bio-impedance takes a few minutes with electrodes on hand and foot. You lie still; there is nothing to feel.
- Most testing is done within a few hours on the first or second day, so therapy can start without waiting.
- Results are usually back within one to three days. Your physician reviews them with you and can add a test the same week.
- The same tests are repeated at the end of the stay or at a set follow-up.
Evidence and limits
The measurement methods themselves rest on strong evidence. Heart rate variability has had standardized measurement and interpretation rules since the 1996 joint task force of the European and North American cardiology societies (Task Force, Circulation, 1996). In myalgic encephalomyelitis and chronic fatigue syndrome, a meta-analysis found altered cardiac autonomic regulation compared with healthy controls, with a lower high-frequency component of resting HRV and a lower maximal heart rate (Nelson et al., Medicine, 2019), which is why HRV is part of the chronic fatigue and Long COVID work-up.
The bio-impedance phase angle reflects cell membrane integrity and body cell mass and has documented clinical relevance as a nutritional and prognostic marker (Norman et al., Clin Nutr, 2012); a systematic review of 48 studies found that a low phase angle correlated with mortality in most clinical settings examined (Garlini et al., Eur J Clin Nutr, 2019). For the cortisol rhythm, a meta-analysis of 80 studies found that a flatter diurnal slope was associated with poorer physical and mental health, most strongly with immune and inflammatory outcomes (Adam et al., Psychoneuroendocrinology, 2017).
What the evidence does not show: blood-based mitochondrial function tests are not standardized across laboratories, and no trial has shown that steering treatment by them improves outcomes, so the hospital reads them as one piece of the picture and never as the sole reason for a therapy. Functional diagnostics complement standard medical diagnostics; when a scan, a biopsy or a specialist opinion is needed, it is ordered.
Who the work-up is for
- Chronic fatigue and unexplained symptoms with normal standard results
- Suspected hormonal imbalance or a disturbed cortisol rhythm
- Autonomic nervous system dysfunction, including post-infectious forms
- Mitochondrial dysfunction assessment in chronic fatigue and Long COVID
- Metabolic syndrome evaluation within the preventive check-up
- Baseline measurement before a treatment program, and monitoring during and after it
How the results change the plan
The work-up decides which modules a program contains and in which order. A flat cortisol curve or a low HRV moves autonomic and sleep work ahead of intensive therapies. A low phase angle changes the nutrition and infusion plan before anything else starts. A mitochondrial result decides whether IHHT or the infusion program comes first. The functional results are read next to the laboratory and immune panels and, where needed, imaging.
The functional tests appear in your written, itemized cost overview (package price plus individual add-ons). A deposit is paid before admission; treatment is self-pay and reimbursement is never promised. Costs and insurance
Questions patients ask
What is the difference between functional and standard diagnostics?
Which tests are included?
How long does testing take and when are results back?
Can functional diagnostics be done without a stay?
What do the results change?
Send the International Office a short history; the initial inquiry is free of charge. The Office then requests the results you already have for a medical review, which shows which functional tests would add something new.
References
- Heart rate variability: standards of measurement, physiological interpretation and clinical use. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. Circulation 1996. PMID 8598068
- Evidence of altered cardiac autonomic regulation in myalgic encephalomyelitis/chronic fatigue syndrome: A systematic review and meta-analysis. Medicine (Baltimore) 2019. PMID 31651868
- Bioelectrical phase angle and impedance vector analysis--clinical relevance and applicability of impedance parameters. Clin Nutr 2012. PMID 22698802
- Phase angle and mortality: a systematic review. Eur J Clin Nutr 2019. PMID 29695763
- Diurnal cortisol slopes and mental and physical health outcomes: A systematic review and meta-analysis. Psychoneuroendocrinology 2017. PMID 28578301
Send a free inquiry
The initial inquiry is free of charge. The International Office reviews your message and your case directly and gets back to you.
- Phone
- +49 8061 398-0
- Hours
- Mon–Thu 08:00–17:00, Fri 08:00–14:00 German time (CET/CEST); in the US Mon–Thu 2–11 a.m. ET, Fri 2–8 a.m. ET.
Munich Airport (MUC), about 60 minutes by car.