CF Newborn Screening Improves Weight and Lung Outcomes, but Has No Impact on Social Inequalities, Study Suggests

Babies diagnosed with cystic fibrosis (CF) through newborn bloodspot screening show better lung function, can better stave off infection with Pseudomonas aeruginosa (the most common bacteria found in CF), and have better weight outcomes than those diagnosed clinically later in life, a large CF registry-based study from the United Kingdom shows.

However, newborn screening had no clear impact on children from disadvantaged backgrounds.

The study, “Impact of newborn screening on outcomes and social inequalities in cystic fibrosis: a UK CF registry-based study,” was published in the journal Thorax.

Estimates state that one in every 2,500 newborns in the U.K. has CF. Most children are diagnosed soon after birth via a bloodspot test.

U.K.’s newborn bloodspot screening (NBS), first established in the 1970s, measures the levels of immunoreactive trypsinogen in the blood, a protein that is commonly elevated in CF. Since 2007, screening includes the measurement of immunoreactive trypsinogen, genetic analysis of mutations in the CFTR gene (the gene defective in CF), and a sweat test.

“The rationale for NBS is to facilitate early intervention, before lung disease is established, which in turn may lead to long-term benefits for people with CF,” researchers stated.

However, it is still not clear whether these screening programs provide long-term health benefits, or whether they help reduce the well-documented worse outcomes of CF children growing up with socioeconomic difficulties.

Researchers at Lancaster University, U.K., and colleagues investigated whether children diagnosed by NBS or those diagnosed clinically later had different clinical outcomes.

The team analyzed data from the U.K. CF registry on lung function, time to chronic infection with Pseudomonas aeruginosa, and nutritional parameters, namely weight for age and body mass index (BMI, a measure of body fat), of over 3,000 children diagnosed with CF, born between 2000 and 2015.

Results showed that, on average, children diagnosed by NBS had greater weight for age standard (SD) scores (an increase of 0.16 SD-scores) compared to those diagnosed clinically. No significant differences were observed for BMI.

Lung function was analyzed by percent forced expiratory volume in one second (%FEV1, a measure of lung function that assesses how much air can be exhaled in one second after a deep inhaled breath).

From 2,216 individuals analyzed for lung function (35% of whom were diagnosed by NBS), the results revealed that on average, patients diagnosed by NBS had better lung function, as shown by an increase of 1.56 percentage points on %FEV1 than those diagnosed clinically.

There was, however, no significant association between diagnosis by NBS and rate of change in lung function, researchers noted.

Time to infection with Pseudomonas aeruginosa was 1.3 times longer for children diagnosed as newborns, which corresponds to a 16% likelihood of developing a chronic infection before age 15, compared to 20% for those diagnosed clinically. This analysis was performed with 3,353 children (46% were diagnosed by NBS), of which 603 became infected.

Regarding health inequalities, children from lower socioeconomic conditions showed lower weight for age and worse lung function detected already at the age of five. There was no evidence of an impact of NBS on health inequalities early in life.

“Our study does not suggest a dramatic reduction in health inequalities after expansion of NBS across the whole of the U.K.,” researchers noted.

Overall, the findings show that “children diagnosed with CF by NBS in the U.K. have better lung function and increased early weight, but NBS does not appear to have narrowed early health inequalities.”

“Further research after longer follow-up may demonstrate an improvement in inequalities over time, but these results suggest that a deeper understanding of the drivers of health inequalities in CF is urgently required such that the underlying factors can be addressed,” the team concluded.