Plain-language · Issue 3 · 2026-10-04
CFTR Variants of Varying Clinical Consequence Show Wide Penetrance Range in CRMS/CFSPID Infants
Editorially reviewed research summaries, context, and limitations.
MacKenzie L Wyatt, Karen S Raraigh, Anna V Faino, et al.
Summary: When newborn screening detects a possible CF-related gene change that does not clearly cause CF, the baby is given a designation called CRMS/CFSPID (CF screen positive, inconclusive diagnosis). Some of these babies will eventually develop CF; others will not. This study pooled data from 25 published reports covering 606 children to ask whether the specific genetic variant found changes the odds of a child later being diagnosed with CF. Among children carrying one uncertain variant paired with one CF-causing variant, 28% eventually received a full CF diagnosis — but the risk varied greatly depending on which uncertain variant was present. Some variants were associated with conversion rates of 50% or higher; others carried much lower risk.
Why it matters: Families of babies with an inconclusive newborn screening result often face months or years of uncertainty and repeated testing. Knowing that the specific genetic variant matters — and that some carry much higher risk than others — gives doctors and genetic counsellors a more useful basis for having those conversations. It also has implications for which gene variants are included in newborn screening programmes, since that choice directly affects how many families face this kind of uncertainty.
What to keep in mind: Although 606 children sounds like a reasonable number, once the data are broken down by individual variant, most of the risk estimates are based on very few children. This makes the specific numbers uncertain — they could shift considerably as more cases are reported. The 25 studies pooled here were conducted in different countries, at different times, and used slightly different rules for what counts as a CF diagnosis, which adds further uncertainty. Studies that followed children for shorter periods will have missed some cases that only became apparent later, meaning the true conversion rates may be higher than reported. These limitations do not undermine the core message — that risk varies meaningfully by variant — but they do mean the precise percentages should be treated as rough guides rather than definitive figures.
Relevance: Cystic Fibrosis
Source: https://pubmed.ncbi.nlm.nih.gov/42629235/
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