Testing
IVCT The in vitro contracture test on a muscle biopsy is the gold standard diagnosis of Malignant hyperthermia.
This is the test that needs to be done on the patient that had the acute MH attack in theatre. If this test is positive we can move on to search for the causative mutation in this patient in order to find a genetic diagnostic tool for the rest of the family.
Without the IVCT results no definitive diagnosis is possible.
The following patients need to contact the MHCSA for IVCT testing:
- All patients that give a personal history of an MH-like crisis under general anaesthetics.
- All patients with a family history of MH or unexpected and unexplained death under general anaesthetics.
- All patients that triggered an acute MH crisis in theatre and survived.
- A family member of a MHS patient where no genetic diagnosis is possible.
- All patients that survived an acute heatstroke episode.
- All patients with Central core disease, multi-mini core disease and King-Denborough.
- Patients with myopathies like Duchene’s 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 info@mhcsa.org.za.
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
Email: info@mhcsa.org.za
When do we do testing?
Wednesday mornings
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. 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.
Genetics
After a patient is tested positive with the IVCT, we do genetic screening in order to search for the specific causative mutation.
The causative mutation is population and family specific. Currently there are 35 causative mutations described in the Caucasian population. The African DNA mapping is still to be researched and described.
Once a causative mutation has been found in an IVCT positive proband, the rest of the family can be diagnosed by testing for this specific mutation.
If none of the causative mutations test positive on the genetic screening, the screening will be re-done on extracted and stored DNA, as new causative mutations are discovered.
The following patients should contact the MHCSA for genetic testing:
- Patient with a positive IVCT.
- Family member of an MHS patient with a genetic diagnosis.
Currently genetic testing is done once a year as part of the annual MHCSA genetic day at the University of Pretoria’s Department of Genetics (Human Genetic Department).
If venous blood samples need to be send at another time, it should be arranged with the MHCSA. In such instance, 20ml venous blood in EDTA tubes on ice (send via Lancet) and specifically arranged with the MHCSA and accompanied by all the necessary clinical information as well as signed informed consent. No isolated blood samples will be accepted.
If a family member gets tested with the IVCT, a small piece of muscle will be send to the genetic lab for RNA extraction and storage. This will be an excellent source for genetic material for the searching process to find the family’s causative mutation.
