Hereditary schemes, introduced in this post (link), can quantify the probability that kids inherit a disease from the parents – and these data are extremely helpful for couples who are planning a pregnancy.  But what if a newborn is suspected to have a monogenic disorder? One of the most reliable tests is the whole exome sequencing (WES), which provides information about possible mutations that might cause a disease, in all the baby’s genes. So far exome sequencing is rarely used due to its limited availability and high costs – and when employed, it enters the diagnostic process quite late – after a long array of other types of genetic testing. However, a study from the University of Melbourne confirmed its incredible power in guiding towards the correct diagnosis, especially if used early on.

In this study, a team of scientists followed closely the diagnostic process of 80 infants who all likely had a genetic disorder. The team sequenced their exomes and concurrently followed the standard diagnostic testing as prescribed by the patients’ physicians. Exome sequencing correctly diagnoses around 57% of the little patients, with just one test. Instead, around 13% of infants were diagnosed via standard methods, usually after substantial prior testing. Strikingly, 11 infants would not have been diagnosed without the exome sequencing.

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Exome sequencing is becoming more and more available and its costs are less and less prohibitive – making it one of the best techniques to speed-up the diagnosis of monogenic disorders at early stages – and as an extra benefit, it also helps to identify healthy carriers and couples at high risk. It seems that in these cases the gain of exome sequencing outweighs its cost.

Bibliography

Zornitza Stark et al. “A prospective evaluation of whole-exome sequencing as a first-tier molecular test in infants with suspected monogenic disorders.” Genet Med 2016 Nov 3;18(11):1090-1096. Epub 2016 Mar 3.