Several labs have been providing cfDNA analysis for the non-invasive prenatal detection of fetal trisomies for the past 3-4 years with robust screening performance. More recently, several NIPT providers have started offering screening for a handful of microdeletions and microduplications in addition to screening for aneuploidies of chromosome 13, 18, 21, X, and Y. We have thoroughly reviewed the data regarding microdeletion/duplication screening with cell-free circulating DNA (cfDNA) and while none of the data are sufficiently robust to be termed a ‘validation,’ we believe the quality and capabilities of the technology are such that incorporating this next iteration of cfDNA analysis into clinical practice is appropriate. More importantly, we are prepared to provide the pre- and post-counseling that lets your patient know what can be learned from the screening test and to translate the associated jargon (‘screening,’ ‘false positive,’ ‘false negative,’ ‘predictive values’) into meaningful and individualized reality.
In the near future, we will be offering this screening as an additional, and optional, component to the standard NIPT screening for aneuploidies of chromosomes 13, 18, 21, X, and Y. It will be presented to patients as an additional (i.e., not standard) offering, not as part of our routine screening protocol. Consequently, you can anticipate seeing patient reports that will include screening data for 7 of the more frequent microdeletions as well as the rare trisomies for chromosomes 16 and 22.
A recent ACOG Committee Opinion #640 (September, 2015) highlights putting NIPT in the context of all first trimester screening options with respect to the limitations as well as the benefits. Because of the absence of clinical trials, as we noted above, the recommendation also does not support the routine use of microdeletion/duplication screening. The Committee Opinion does focus on the counseling process that should accompany offering any and all of the options for prenatal screening and testing. This, of course, is the standard IMG provides for all its services. We will be offering such screening as an option being very mindful of these considerations and will be monitoring the clinical impact carefully.
Additionally, because of the limitations of cfDNA analysis, we believe such screening should not be used as a follow-up to an abnormal ultrasound finding, but that such a finding should be followed by a diagnostic procedure and analysis (CVS or amniocentesis).
The capability to screen for a larger list of genome-wide variants (called copy number variants, or CNVs) by cfDNA testing is likely to grow to a higher resolution than is currently available. We will continue over time to expand our capacity to provide you and your patients options for wider and earlier screening, which we anticipate will include early ultrasound scanning, non-invasive genome screening ,as well as high resolution analysis of the genome following an invasive procedure.