Skye Whiteman's daughter Brydee was diagnosed with a rare childhood blood cancer at five-and-a-half months old.

An active child, Brydee had her bone marrow transplant in May last year, following six months of chemotherapy to treat her Juvenile Myelomonocytic Leukaemia.

Mrs Whiteman said her daughter slowed down a bit during treatment but "flew through" the transplant. Afterwards Brydee, now two, was one of the early beneficiaries of a new blood test.

The test which enables doctors to more accurately and rapidly assess the success of a bone marrow transplant has been hailed a lifesaver because of its ability to give doctors more time to respond to changes in a patient's condition.

Developed over five years by a team at the Murdoch Childrens Research Institute, it can detect whether the bone marrow transplant has been rejected, or if the disease is still present, much earlier than previous techniques.

Known as the Organ Health BMT test, it cuts the wait time for results from up to two months to within a week.

This means doctors are able to intervene significantly and make changes to the cocktail of drugs patients are prescribed post-transplant. The earlier intervention boosts the patient's chances of a successful bone marrow transplant.

"A lot can happen in eight weeks," said Damien Bruno, laboratory geneticist and co-inventor of the test. "And we know anecdotally that this test is saving lives."

The test works by measuring the amount of donor DNA in the patient's blood. A result of 100 per cent is ideal but lower readings of about 70 per cent are okay initially, as long as the level climbs over time.

Outlined in the journal Experimental Hematology on Wednesday, the test has been used at the Royal Children's Hospital since 2016.

"The Children's Hospital jumped on board pretty quickly," Dr Bruno said. "It offered such a significant improvement on the test the hospital was using that they moved very quickly - perhaps quicker than they would normally."

Royal Children's Hospital doctor and researcher at the Murdoch Childrens Rachel Conyers said she had no doubt the test would improve transplant outcomes for patients.

"This can, and will, impact upon patient survival," she said. "It gives the clinician the opportunity to act early if post-transplant alterations to the graft are necessary."

The blood test was rolled out at the Victorian Clinical Genetics Services laboratory, which Dr Bruno heads.

As well as faster results, the new test can guarantee a result every time for every patient. Previously not all patients could get a result. The test would also be applicable to transplant patients with other immunological disorders such as haemophagocytic lymphohistiocytosis, storage disorders such as mucopolysaccharidosis and bone marrow failure disorders such as aplastic anaemia.

According to the Australasian Bone Marrow Transplant Recipient Registry, more than 2000 transplants are preformed each year.

Almost a year on from her transplant, Brydee is monitored with fortnightly blood tests which will become less frequent over time.

"She has her sassy attitude back now," Mrs Whiteman said. "The hospital has been incredible, we are just so grateful."