What specific investigations should be conducted to confirm a diagnosis of malignant hyperthermia in a patient presenting with hyperthermia and muscle

To confirm a diagnosis of malignant hyperthermia (MH) in a patient presenting with hyperthermia and muscle rigidity, the key investigations include:

• In vitro contracture testing (IVCT): This is the gold standard diagnostic test, involving a muscle biopsy (usually from the vastus lateralis) to assess muscle contractile response to caffeine and halothane. A positive test confirms MH susceptibility NICE CKS Rosenbaum & Miller 2002.
• Genetic testing: Molecular analysis for mutations in the RYR1 gene and, less commonly, CACNA1S gene can support diagnosis by identifying known pathogenic variants associated with MH susceptibility. Genetic testing is less sensitive than IVCT but useful for family screening and when biopsy is contraindicated NICE CKS Ali et al. 2003Hopkins et al. 2018.
• Clinical and laboratory investigations during the acute episode: These include monitoring elevated serum creatine kinase (CK), hyperkalemia, acidosis, and elevated temperature, which support the clinical suspicion but are not diagnostic alone NICE CKS Hopkins et al. 2018.

Summary: Definitive diagnosis relies primarily on IVCT muscle biopsy testing, complemented by genetic testing for known mutations. Acute biochemical abnormalities assist clinical recognition but do not confirm diagnosis NICE CKS Rosenbaum & Miller 2002Ali et al. 2003Hopkins et al. 2018.