Pre-marital screening for spinal muscular atrophy in the UAE and Saudi Arabia could reduce the number of cases and save tens of millions of dollars in expensive treatment each year, a study has found.
Testing whether couples are carriers for the genetic disease – which affects children – would reduce the number of spinal muscular dystrophy (SMA) patients and cut the need to buy a drug previously described as the most expensive in the world.
The money saved could be used to fund premarital screening for hundreds of other rare conditions.
"Besides preventing new cases, we show that the cost of premarital screening is really almost insignificant when compared to postnatal treatment of the disease," said Dr Ahmad Abou Tayoun from Al Jalila Children’s Specialty Hospital in Dubai, the first author of the study.
Dr Abou Tayoun and his team of researchers calculated cases of SMA in the native populations of the UAE and Saudi Arabia.
What is spinal muscular atrophy?
SMA affects the motor neurons – nerve cells that send messages to the muscles – and results in progressive muscle weakness. It can make walking impossible or difficult and affects swallowing and breathing.
In type 1, the most severe form which affects about half of those diagnosed, the child often dies from respiratory failure before reaching the age of two.
Even children affected by the less severe type 2 may be unable to walk as a result.
Other types emerge in older children or adults and cause less severe but still significant, symptoms.
The disease is usually the result of a child having two faulty copies of the survival motor neuron 1 (SMN1) gene, the normal form of which is needed to function properly.
If a child inherits a faulty form of the gene from one parent but an ordinary one from the other, they will develop normally, because the effect of the malfunctioning gene is masked by the normal form, making SMA a "recessive" trait. Such an individual is a carrier for the condition.
If two adults who are carriers for this faulty form of SMN1 marry, there is a one in four chance that any child they have will inherit both faulty forms and go on to develop SMA.
The costs
The study, Spinal muscular atrophy genetic epidemiology and the case for premarital genomic screening in Arab populations, was released last month as a preprint on Europe PMC before being reviewed by other researchers.
In it, scientists carried out genetic screening on 1,252 healthy Emirati babies born at 11 maternity hospitals in the country. They found about 1.5 per cent of the Emirati population to be carriers.
Al Jalila Children’s Specialty Hospital, Dubai
Their analysis also showed that out of every 5,990 live births in the Emirati population, one child will go on to develop SMA.
Based on their genetic analysis, the researchers estimated about five Emirati children a year are likely to be born with SMA, resulting in a cost of $10.5 million for gene therapy, treatment in which the faulty form of the gene is replaced with a normal type.
The total cost of SMA screening for all Emirati couples planning to get married is a fraction of this, at about $490,000, the researchers calculated.
Were such a screening programme introduced, there would be additional costs. In cases where the husband and wife are carriers, they could undergo in-vitro fertilisation (IVF) and preimplantation genetic testing (PGT), with only embryos not at risk of developing SMA being implanted.
"Premarital screening results will inform couples about their options to prevent pregnancies that are affected with SMA," said Dr Abou Tayoun, who is director of the hospital’s genomics centre.
"Premarital screening will be highly effective in our setting to manage risks and prevent the associated distress and suffering caused by SMA and other recessive diseases."
Compared with the cost of treating a child with SMA, IVF and PGT are inexpensive, at about $30,000 for every couple, meaning about $10 million would be saved by introducing premarital screening in the UAE.
SMA treatment
Gene therapy treatment for SMA has dramatically improved the outlook for children with the condition, but it is very costly.
Zolgensma, a gene therapy medicine that is given once, has been described as the most expensive drug in the world, with a single treatment said to cost about $2 million. Al Jalila Children’s Specialty Hospital is one of the places where the drug is administered.
The new study estimated the incidence of SMA in Saudi Arabia to be one in 3,125 live births, which works out at about 160 children being born each year who will develop the condition.
The estimated treatment cost in Saudi Arabia, $336 million, dwarfs the potential spending on premarital screening of about $7 million and the combined costs of IVF and PGT, about $4.8 million. This gives a saving of about $324 million.
"The cost savings due to premarital screening for this one disease are sufficient to fund more comprehensive premarital genomic-screening programmes encompassing hundreds of recessive disorders in both countries," the researchers wrote.
Genetic analysis like that outlined in the study has been carried out less often on Arab populations, with people of European descent having been studied more comprehensively.
"It is extremely important to conduct such studies to characterise the epidemiology of the large number of inherited diseases in Arab populations," Dr Abou Tayoun said. "This information will guide the most effective management or preventive plans."
The researchers chose SMA "as a prototype for rare diseases", he said, because there were now several treatment options, including gene therapy.
"Our study is probably one of the first to put a price tag on the burden of a rare disease and to build, based on that, an economic case supporting the efficacy and cost-effectiveness of wider premarital genomic screening programmes," he said.
