Architecture C Diagnostic Concepts
The metabolic reserve hypothesis (Architecture C Diagnostic Concepts) suggests several diagnostic approaches targeting reserve measurement and risk stratification. These range from immediately implementable screening panels to research-stage cellular assays.
1 Composite Metabolic Reserve Score (MRS)
A clinically practical composite score estimating metabolic reserve from available measurements: \[ \text{MRS} = w_1 dot (\text{ferritin} / 100) + w_2 dot (\text{BH4} / \text{BH4}_\text{ref}) + w_3 dot (\text{VO}_2 \text{max} / \text{VO}_2 \text{max}_\text{predicted}) + w_4 dot (\text{CBF} / \text{CBF}_\text{ref}) + w_5 dot (1 - \text{ND}_\text{burden}) \] where \(\text{ND}_\text{burden}\) = sum of binary indicators (ADHD = 0.15, ASD = 0.20, hEDS = 0.10, migraine = 0.05, GCH1 homozygous = 0.10). Practical challenge: BH4 and CBF are not routine clinical measures. A simplified version using only ferritin + VO2max + neurodivergent diagnosis could be implemented in primary care as a screening tool. However, the simplified version currently lacks calibrated weights, clinical cut-off values, and actionable interpretation guidance — a GP receiving a raw score would have no evidence-based threshold for deciding intervention intensity. Use case: Identify high-risk individuals before infection (prevention) and stratify treatment intensity (lowest MRS = most aggressive metabolic support the severity-stratified reserve protocol).
2 MtDNA Haplogroup as a Reserve Stratifier
The composite Metabolic Reserve Score above could be extended by incorporating mtDNA haplogroup as a biological anchor for the reserve estimate. Billing-Ross et al. demonstrated that haplogroups J, U, and H associate with distinct symptom severity profiles in established ME/CFS (certainty 0.45; see Section:mtdna-haplogroup-symptoms in Chapter:cross-disease). Haplogroup determination is a one-time, low-cost test (targeted mtDNA sequencing or consumer genomics panels such as 23andMe). Adding haplogroup as a reserve-modifier node — haplogroup H as lower reserve ceiling, haplogroup U as higher reserve floor — could improve individual-level risk stratification within the MRS framework.
3 Urinary Neopterin:Biopterin Ratio as Non-Invasive BH4 Screen
Neopterin is produced when GTP cyclohydrolase I activity is diverted toward immune activation rather than BH4 synthesis. An elevated neopterin:biopterin ratio indicates both immune activation AND BH4 depletion — both relevant to Architecture C. Practical advantages: Non-invasive urine collection, can be done at home and mailed. HPLC measurement is standard and cheap (~$30–50 per sample at specialty labs). Current limitations: No validated clinical reference range exists for ME/CFS populations; HPLC pteridine measurement has no CPT/INAMI billing code in most countries; and elevated neopterin also occurs in renal failure, HIV, and active malignancy, creating false-positive risk in patients with these comorbidities. Interpretation: High ratio = high immune activation + low BH4 = low metabolic reserve = candidate for BH4 support (Chapter Supplements and Nutraceuticals, Section Vitamin B6/P5P for Glu→GABA Conversion).
4 Thermoregulatory Function Biomarkers
5 Pre-Infection Risk Screening Protocol for Neurodivergent Patients
For patients with known neurodivergent diagnoses, a tiered screening protocol could identify those at highest metabolic reserve risk: Tier 1 (any primary care, ~$100): Ferritin (target \(> 100\) ng/mL), CBC with differential, vitamin D (target \(> 50\) ng/mL), CRP, ESR. Interpretation: Ferritin \(< 100\) ng/mL → consider iron repletion standard iron repletion guidelines for neurodivergent patients. Vitamin D \(< 50\) ng/mL → supplement to target. Elevated CRP/ESR → investigate active inflammation before attributing to ME/CFS predisposition. Normal results do not exclude low metabolic reserve — Tier 1 captures only the most accessible markers. Tier 2 (specialist, ~$300): Urinary neopterin:biopterin ratio, tilt table or NASA lean test (CBF proxy) (note: tilt table testing is a cardiology/autonomic specialty procedure requiring referral in most health systems; the NASA lean test is a simpler office-based alternative), serum zinc/copper/B12/folate, CPET if ambulatory (VO2max, anaerobic threshold). Tier 3 (research only, ~$2,000+): GCH1 genotyping, FDG-PET (cerebral glucose metabolism), PBMC respirometry. Actionability: Tier 1 is implementable today. Tier 2 requires specialist referral. Tier 3 is research-only.