2026 — van der Spek — autonomic-receptor AAbs are trans-chronic-pain, NOT CRPS-specific
One-paragraph summary
Cross-sectional, blinded analysis of serum autoantibodies against the muscarinic M2 receptor (M2R), β1-adrenergic (β1AR), and β2-adrenergic (β2AR) receptors across 22 CRPS, 25 other-chronic-pain, and 23 healthy-control participants (n=70 total). Patients classified by Budapest criteria. ELISA measurement. Key empirical result is negative for CRPS specificity: M2R autoantibody levels were higher in both CRPS and other-chronic-pain compared to HCs (MDs 0.37 [0.22-0.51] and 0.31 [0.19-0.44]); β2AR levels higher in other-chronic-pain vs HCs (MD 0.29 [0.04-0.54]) but not significantly elevated in CRPS (MD 0.21 [-0.01-0.42]); β1AR levels did not differ between groups. No meaningful differences were observed between CRPS and other-chronic-pain for any receptor. Seropositivity for any AAb: 55% CRPS, 44% other-chronic-pain, 22% HCs. The conclusion is unequivocal: elevated autonomic-receptor AAbs are observed across chronic-pain conditions but are not specific for CRPS. For the project, this paper functions as a discipline check against the B3 bridge (CRPS + IgG-passive-transfer) — autonomic-receptor AAb elevation is a trans-chronic-pain phenomenon, not a CRPS-defining one, and the project's framing of CRPS-IgG-transfer experiments as a cure-path anchor needs to be qualified accordingly.
Claims as triples
m2_muscarinic_autoantibody — present_in → crps[evidence: MD 0.37 vs HCs in CRPS; confidence: established]m2_muscarinic_autoantibody — present_in → fm_central_only[evidence: MD 0.31 vs HCs in other chronic pain category; confidence: emerging]autonomic_autoantibody_panel — NOT specific_to → crps[evidence: no meaningful difference between CRPS and other chronic pain for any receptor tested; confidence: emerging]autoantibody_seropositivity — present_in → chronic_pain_general[evidence: 55% CRPS, 44% other chronic pain, 22% HCs; confidence: emerging]
Triangulation notes
- Discipline check on B3 (CRPS + IgG-passive-transfer) bridge framing. The bridge correctly identifies an anchoring set of cross-condition autoantibody-mediated chronic-pain experiments, but van der Spek shows the M2R/β2AR AAb signal is not CRPS-defining. The mechanistic anchor remains valid (autoantibody-mediated chronic-pain causation, demonstrated by Goebel 2021 FM IgG passive transfer in mice) but the cohort interpretation needs to treat M2R/β2AR seropositivity as a chronic-pain marker rather than a CRPS-discriminator.
- Reconciles with Azcue 2026 (head-to-head PCC vs ME/CFS): autonomic-receptor AAbs differ in profile (β2 elevated in ME/CFS, M3 borderline-high in PCC) but not in absolute presence/absence across chronic-pain phenotypes. The disease specificity sits in the AAb pattern, not the seropositivity binary.
- Strengthens the cohort-design recommendation that biomarker-mapping should measure the AAb panel as a continuous-spectrum trans-chronic-pain stratifier (not a CRPS-binary).
- Negative-result discipline. The project explicitly tracks negative findings to discipline drift; ingestion of well-conducted negative results like this one is part of the over-regulation audit's stated approach.
Open questions raised
- If M2R/β2AR AAb seropositivity is high across chronic pain (55% CRPS, 44% other), what fraction of FM patients in established FM cohorts is seropositive at the same threshold?
- Is there a quantitative threshold (titer level) above which the AAb signal becomes CRPS-discriminating, or is the trans-condition pattern stable across the full titer distribution?
- Does AAb seropositivity (within chronic pain) predict responder status for plasmapheresis+IVIG or FcRn-blocker interventions?