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Researchers Establish Spectrum of Gene Variants Linked to Cystic Fibrosis in Nonwhites

NEW YORK (GenomeWeb) – A team led by Stanford University researchers have identified novel gene variants linked to cystic fibrosis in nonwhites, which they said can be used to improve screening tests for the disease.

As they reported today in the Journal of Molecular Diagnostics, cystic fibrosis occurs less frequently in nonwhites than in whites, but nonwhites are usually diagnosed later in life than whites, making them more difficult to treat. Newborn screening tests for cystic fibrosis are not optimally designed to catch CFTR gene variants linked to the disease in nonwhites.

"In contrast to thoroughly analyzed white CF populations, the CFTR variant spectrum and prevalence in black, Asian, Native American, and Middle Eastern CF patients have not been elucidated completely," the team wrote in its paper. "Such knowledge gaps can lead to racial-ethnic disparities in the clinical sensitivity of neonatal screening algorithms and molecular diagnostic testing."

In order to establish a wider range of nonwhite-linked CFTR variants, the team examined previously gathered CFTR genotyping data of 22,206 non-Hispanic whites, 1,955 Hispanics, 1,214 blacks, 156 Asians, and 171 Native Americans. They found that 90 percent of whites and 83 percent of Native Americans with CF have a specific mutation called p.Phe508del, but that 30 percent of Hispanics, 38 percent of blacks, and 41 percent of Asians didn't have it.

They then used direct DNA sequencing on 140 of the nonwhite individuals and found that 89 of them had two CFTR variants, including seven novel variants. Multiplex ligation-dependent probe amplification identified 14 rearrangements in the remaining 51 patients, six of which were novel, the researchers reported.

"A cross-sectional analysis of genotyping data from the CF Foundation Patient Registry was performed, comparing 3,496 nonwhite patients with 22,206 white CF patients. Patients of Hispanic, black, or Asian ancestry were less likely to have two identified CFTR variants, and more likely to carry no mutations on the commonly used 23 mutation carrier screening panel," the team wrote.

This study could "facilitate equity in mutation detection between white and nonwhite or mixed-ethnicity CF patients," they added, which would make early diagnosis more possible for these patients.