The underlying genetic cause for your child’s clinical features can be due to many different types of genetic variations. The genetic variations that FirstStepDx PLUS looks for include deletions (missing genetic material) and duplications (extra genetic material) on the chromosomes. The genetic variations that NextStepDx PLUS looks for are much smaller and can’t be detected by FirstStepDx PLUS.
One way to look at the difference between how the two tests work is to compare them to a book. FirstStepDx PLUS looks for missing or duplicated chapters in a book. NextStepDx PLUS looks for misspellings within a single word. Neither test can do the other’s job. If FirstStepDx PLUS does not find an underlying genetic cause for your child's clinical features, performing a NextStepDxPLUS test is a way to look at the "book" of your child's genetic information in a totally different way.