2023-06-22 17:12:03
Quebec is one of the last places in North America where systematic screening is not offered, as is done in all American states and several Canadian provinces.
Babies with severe combined immunodeficiency lack an immune system, which makes them vulnerable to even the slightest infection. Their life expectancy is less than a year without treatment.
The disease is often detected when the baby begins to show various health problems, such as growth retardation, diarrhea or recurrent infections. Gene therapy is possible in some cases, but the usual treatment is a bone marrow transplant which gives the little patient an immune system.
“These are heavy treatments and survival following these procedures, especially following the marrow transplant, was around 70%, said Dr. Elie Haddad, from CHU Sainte-Justine. We had already published in the past that we might not get above this 70 or 75%.”
But a recent study published in the medical journal The Lancet by Dr. Haddad and colleagues clearly shows that survival rates increase dramatically ― up to 92.5% ― following the transplant if SCID was detected at birth, rather only following the baby has been sick several times.
SCID affects approximately one in 50,000 babies, which represents one or two births per year in Quebec. Screening is done from the drop of blood which is taken anyway on blotting paper from the heel of all newborns.
“Screening makes it possible to diagnose the immune deficiency and therefore to avoid infections before the transplant and to prevent children from dying without even knowing that they have an immune deficiency”, summarized Doctor Haddad.
“If the tests confirm that there is a serious immune deficiency, then that changes everything because we can isolate them, we can take care of them before they have an infection and we can transplant them quickly and in doing that, we completely change their prognosis, their quality of life, their survival.”
Caring for the little patient from birth, rather than following multiple health issues, means he will be in much better shape by the time of the bone marrow transplant, which will help improve his chances of survival, the specialist.
An infection at the time of the transplant “dramatically complicates things”, he specified, in addition to reducing survival and immune reconstitution.
Going to the transplant with few or no infections “changes everything,” Dr. Haddad said.
Routine screening for DICS began to spread in the United States around 2009, Dr. Haddad said, and is now offered in all US states. It has also been offered for several years in seven Canadian provinces.
This gradual deployment and the gradual increase in the number of babies screened allow scientists to compare two cohorts, namely those of babies born before systematic screening and that of babies born following.
“It’s really compelling evidence,” said Dr. Haddad. That’s why we got published in The Lancet. It is very rare to be able to prove with certainty that a screening works. From an epidemiological point of view, comparing two populations in the same period is the ‘top’.
Systematic screening is not yet offered in Quebec, but discussions with the Ministry of Health and Social Services are very advanced and the measure should be in place within a few months. “When you implement this kind of thing, you have to implement it well. It’s not regarding wanting to absolutely save a month or two, then implanting something that doesn’t work,” said Dr. Haddad.
“I’m very confident it’s going to be done quickly and done very well,” he added.
Systematic screening has already begun in northern Quebec, as data have detected a slightly higher prevalence of SCID in Aboriginal populations. Since the incidence of tuberculosis is also higher in these populations, and since the prevention of tuberculosis involves vaccination with bacille Calmette-Guérin, it is important to identify babies to whom this bacillus should not be administered, explained Dr. Haddad, “to avoid turning a complicated situation into an ultra-complicated situation”.
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