Invitae is a College of American Pathologists (CAP)-accredited and Clinical Laboratory Improvement Amendments (CLIA)-certified clinical diagnostic laboratory.

This test determines SMN1 and SMN2 exon 8 copy number by Droplet Digital PCR (ddPCR). Due to sequence similarity between SMN1 and SMN2, the copy number of exon 8 is used to infer the copy number of the entire gene. The ddPCR method is based on partitioning a PCR reaction with primers and probes for SMN1/2 and a copy number reference into 20,000 individual droplets, thermocycling, then measuring the endpoint fluorescence intensity of each droplet. The instrument software provides a count of the number of droplets for each genotype and generates an absolute count of the number of copies of each target in the reaction and thus the copy number. Use of ddPCR for both copy number and single-base discrimination is a well-established technology supported by commercial reagents, instrumentation, and analytical tools. Reported variants are not confirmed by an orthogonal technology.

Based on validation study results, this assay achieves >98.5% analytical sensitivity and specificity for SMN1 and SMN2 exon 8 deletions. Mosaic copy-number deletions and duplications may not be detected. This report reflects the analysis of an extracted genomic DNA sample. In very rare cases (such as circulating hematolymphoid neoplasm, bone marrow transplant, recent blood transfusion, or maternal cell contamination), the analyzed DNA may not represent the patient's constitutional genome.