The in vitro contracture test on a muscle biopsy is the gold standard diagnosis for Malignant hyperthermia.
This is the test to phenotype the index patient before we genotype the patient in order to find the family's causative mutation.
Without the IVCT results no definitive diagnosis is possible.
Refer the following patients for IVCT testing:
- All suspected cases of MH that give a personal history of an MH-like crisis under general anaesthetics.
- Patients with a family history of MH or unexpected death under general anaesthetics
- Patients that triggered an acute MH crisis with a LCRS rank of 3 to 6 and survived
- Family member of MHS patient where no genetic diagnosis is possible
- Patient that survived an acute heatstroke episode
- All patients with Central core disease, multi-mini core disease and King-Denborough.
- Patients with myopathies like Duchennes dystrophy and certain other myopathies that suffered an MH-like attack.
- Patients that survived a Neuroleptic Malignant syndrome.
We do the IVCT testing at Midstream Mediclinic on Wednesdays. Book online or email firstname.lastname@example.org.
Who should enquire about testing?
- All patients with a history of an MH episode
- All patients with a family history of MH
- All patients with a family history of an unexplained anaesthetic death
- All patients with a history of MMR
- All patients with King-Denborough syndrome
- All patients with Central Core Disease
- All patients with Multi-minicore Disease
- All patients with Nemaline rod myopathy
- All patients with a history of heatstroke
- All patients with a family history of heatstroke
- All patients with congenital myopathies
- All patients with Anaesthetic induced rhabdomyolysis
Where do we do testing?
Malignant Hyperthermia in vitro contracture laboratory at Midstream Mediclinic
Address: Cnr Midstream Drive Midstream Hill Boulevard, Midstream Hill, 1692.
Midstream Hill Medical Centre Suite 209
When do we do testing?
What does the test involve?
The in vitro contracture test is done in our MH laboratory at Midstream Mediclinic on a muscle sample (4cm x1cm) taken in theatre under a trigger-free general anaesthetic. The muscle biopsy will be done by Orthopaedic surgeon Dr Phillip de Lange
and the MH-safe trigger free anaesthetic will be administered by specialist anaesthetist and MH specialist Dr Hannah Brand. The muscle biopsy will be taken by atraumatic technique and will be minimally invasive. The skin incision will be approximately 5cm on the inner aspect of the thigh above the knee. A femoral nerve block will be administered for post-operative pain. The duration of the procedure is 45-60minutes. Depending on individual pain control patients will be able to go home the same day or at most the next morning. After the muscle sample has been taken, muscle will be used in the MH laboratory to do the gold standard diagnostic IVCT test to determine MH susceptibility.Our laboratory technician is William McMahon.
Results will be available the same day of testing. The IVCT is a very sensitive (99% sensitivity) and a very specific (97% specificity) test, in other words there is a very low false positive and negative rate.
The muscle biopsy is a safe procedure but local pain in the wound area can be expected for about 10 days and sport activity can safely be resumed after 4-6 weeks.
Rare complications include haematoma, infection and wound dehisence.
Only children 10 years and older can be tested with the IVCT.
How do I get tested?
After a patient has tested positive with the IVCT, genetic screening of the RYR1-gene (for known causative mutations) can be carried out in order to search for the specific causative mutation.
The causative mutation is population and family specific. Currently there are 35 mutations that have been shown to cause MHS in the Caucasian population. Causative mutations in African populations is still to be researched and described.
Once a causative mutation has been found in an IVCT positive proband, diagnostic testing can be offered for the rest of the family for their specific mutation.
If none of the known causative mutations are detected at the time of the genetic screening test, the extracted DNA will be stored to be tested later as new causative mutations are discovered.
Refer the following patients for genetic testing:
- Patient with a positive IVCT
- Family member of an MHS patient with a genetic diagnosis
Currently genetic testing (for the known causative mutations)is done once a year as part of the annual MHCSA genetic day at the University of Pretoria's Department of Genetics (Human Genetics Section). Should testing need to be carried out at any other time, it must be arranged with the MHCSA. In such instances, 20ml venous blood in EDTA tubes (send via Lancet) and specifically arranged with the MHCSA and accompanied by all the necessary clinical information as well as signed informed consent must be sent. No isolated DNA samples will be accepted.
"Refer a patient and save a family"