Although advances have been made in genetic screening for malignant hyperthermia susceptibility, an incomplete understanding of the genetics of MH susceptibility means that DNA testing currently has only a limited utility. Genetic screening can identify 35 to 40% of true MH cases but it cannot be used to exclude MH susceptibility.
Muscle biopsy testing
Definitive diagnosis requires an open muscle biopsy and pharmacological contracture studies known as the in vitro contracture tests (IVCT).
IVCT is a highly specialised procedure that requires freshly excised muscle samples. The Malignant Hyperthermia Investigation Unit at St James’s University Hospital, Leeds, is the only centre providing IVCT in the UK. Patients requiring the IVCT will need to spend up to two nights in Leeds. The procedure is done under a type of local anaesthetic through a 2 – 2 ½ inch (5-7 cm) incision in the lower medial aspect of the thigh.
The referral of an index case for investigation will usually be made by the anaesthetist who managed the index case. It is their responsibility to make this referral as they can provide all the information to the MH unit that is required to determine if investigation is appropriate and then what tests to advise in the first instance.
Access and Funding for MH testing
Access to the MH unit diagnostic services is provided on a first come first serve basis, except when a clinical need supervenes. For example, we are able to give priority to a patient who needs confirmation of diagnosis before they are able to undergo a required surgical procedure.
Funding for MH testing of patients eligible for NHS treatment is provided through the NHS. At present the MH diagnostic service is funded on a patient by patient basis through Clinical Commissioning Groups in England and through the Health Board or Panel in Scotland, Northern Ireland and Wales. The requirement for us to have confirmation of funding before we can proceed with investigations is one of the reasons why the MH unit may not be able to offer appointments at short notice.
Patients who are not eligible for NHS treatment may still access the MH Unit diagnostic services, but they will be charged the full cost of the procedure by the hospital. Details of these costs can be obtained through the MH Unit administrator.