Long-term Follow-up Needed to Assess Newborn Screening for Lysomal Storage Disorders

Long-term Follow-up Needed to Assess Newborn Screening for Lysomal Storage Disorders

The benefits of newborn screening for lysosomal storage disorders such as Gaucher disease were not directly apparent 15 months after Illinois launched statewide screening.

Long-term follow-up is needed to assess the true benefits and risks of the screening, researchers from the Feinberg School of Medicine of Northwestern University write in their report, “Newborn Screening for Lysosomal Storage Disorders in Illinois: The Initial 15-Month Experience.”

Among 219,973 infants screened for disease, Gaucher was detected in five babies. Fabry and Pompe diseases were the most common lysosomal storage disorders, with 26 and 10 infants detected by screening, respectively.

This was higher than has been reported for Fabry and Pompe disease in earlier studies, according to the study, which was published in the Journal of Pediatrics.

The rate of Gaucher disease was, on the other hand, similar to what earlier studies suggested. The screening also identified one infant with mucopolysaccharidosis (MPS) type 1 and two infants with Niemann-Pick disease type A/B.

But the study showed that initial results reported higher rates for several of the conditions, particularly for MPS-1. Most of the children who initially tested positive for disease in screening had what researchers call pseudodeficiency — a genetic or molecular fault in a protein that does not appear to cause disease.

Among children who initially tested positive for one of the five diseases, physicians could not confirm a diagnosis for 22 of them despite extensive follow-up tests, which included screening for genetic mutations.

Researchers also noted that many of the infants diagnosed did not have an apparent disease at diagnosis. This suggests that they have late-onset disease, but only a long-term follow-up assessment can evaluate that diagnosis accurately, researchers said.

Among the five children detected with Gaucher disease, none had symptoms of the disease at diagnosis and at the time of writing the report, none received enzyme replacement therapy.  One was judged to have type 1 disease and two are being monitored as physicians suspect they might have Gaucher disease.

The study did not detect any false-negative results — cases in which doctors missed signals that an infant had a lysosomal storage disorder.

So while results of the screening program were generally positive, the research team emphasized that screening results that are not able to classify an infant as either affected or unaffected constitutes a problem.

To determine how screening impacts the outcomes of these children, as well as those judged to have a late-onset form of disease, it is necessary to continue following these children over time, researchers concluded.