Single Muscle Fibre Calcium Wave Frequency Assay for Malignant Hyperthermia Diagnosis: an Exploratory Validation Study.

Summary

In a 30-patient exploratory validation, a single-fiber Ca2+ wave frequency assay directly assessing RyR1 responsiveness to halothane discriminated MH-susceptible from normal muscle with 92% sensitivity and 88% specificity, comparable to IVCT. Caffeine responses did not differentiate groups, underscoring halothane-specific diagnostic utility.

Key Findings

• Halothane induced regenerative Ca2+ waves more frequently in MHS versus MHN muscle fibers at 0.5 mM (36.5% vs 0%) and 1 mM (77.5% vs 23.1%).
• Ca2+ wave frequency was higher in MHS fibers across all tested halothane concentrations; caffeine did not differentiate groups.
• A threshold of 1 mM halothane and 1.57 waves/min achieved 92% sensitivity and 88% specificity versus IVCT.

Clinical Implications

If validated at scale and standardized, CaWFa could reduce reliance on large muscle biopsies, expedite MH risk assessment, and broaden access to testing. Implementation will require equipment (confocal microscopy), operator training, and quality controls.

Limitations

• Small, single-center exploratory sample (n=30) without external validation.
• Specialized ex vivo protocol and equipment may limit immediate generalizability; standardization is needed.

Future Directions

Multi-center diagnostic accuracy studies with standardized protocols, operator training, and assessment of feasibility, cost-effectiveness, and integration with genetic testing (RYR1 variants).