CF underrecognized outside U.S. and Europe, better testing needed: Study
Researchers also call for increased access to effective treatments worldwide
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Cystic fibrosis (CF) likely affects as many babies in parts of Asia, Africa, and South America as in Europe and the U.S., and better genetic testing and broader access to effective treatments are urgently needed worldwide, a study suggests.
The study, “Analysis of the Genome Aggregation Database (gnomAD) reveals a global burden of cystic fibrosis and the need for improved diagnosis and care,” was published in eBioMedicine by three U.S. researchers.
True frequency of CF in non-European groups is less clear
Mutations in the CFTR gene cause CF. This gene encodes a protein that helps control the movement of salt and water in and out of cells. When this protein is missing or faulty, thick and sticky mucus builds up in the lungs and other organs, leading to symptoms such as infections and difficulty breathing.
Most studies on CF have been done in people of European ancestry. The true frequency of CF in non-European groups is less clear, partly because of limited testing and healthcare access.
To better estimate how common CF is worldwide, the researchers used data from the Genome Aggregation Database (gnomAD). This database includes genetic information from more than 800,000 people across 25 countries. The researchers identified disease-causing mutations and used a genetic model to estimate how often CF may occur based on United Nations birth statistics.
It was estimated that 44 to 52 babies of European ancestry per 100,000 people are born with CF each year. In African or African American populations, the rate was 11 to 14 per 100,000. Other rates were 7 per 100,000 in admixed Americans (with mixed ancestry, common in Latin America), 6 per 100,000 in South Asians, 4 per 100,000 in East Asians, and 0.2 to 1 per 100,000 in Middle Eastern populations.
Improved diagnostics, therapeutics, and access to [highly effective CFTR modulators] will benefit thousands of people with CF globally.
Although the rates per 100,000 births are lower outside Europe, higher birth rates in many countries change the overall picture. For example, the researchers estimated 1,426 to 1,582 babies with CF are born each year in India. In Brazil, the rate was 330 to 390 per year. By comparison, there may be about 1,000 new cases per year in the U.S. and 300 in the U.K. each year.
Definitive CF diagnosis depends heavily on genetic screening panels, which test for common mutations in the CFTR gene. Many panels were designed using data from European populations. However, these panels may miss more than 70% of disease-causing genetic mutations in non-Europeans. The expanded Wisconsin panel performed best, missing 1% to 30% of disease-causing mutations.
At the same time, access to treatments is limited. Up to 40% of disease-causing genetic mutations in non-Europeans are not currently eligible for highly effective CFTR modulators, which work by improving the function of certain faulty versions of the protein.
Previous reports suggested that CF is rare outside Europe, often presenting rates per 100,000 people rather than per 100,000 births. However, birth rates are much higher in many parts of Asia, Africa, and South America.
Our findings show that the “absolute number” of babies born with CF “may be comparable” worldwide, the researchers wrote. “Improved diagnostics, therapeutics, and access to [highly effective CFTR modulators] will benefit thousands of people with CF globally.”
