Screening tests for SMA commonly involve the extraction of DNA from samples of dried blood spot (DBS) and the use of real-time quantitative PCR to determine the presence or absence of the responsible gene,SMN1, although PCR and digital PCR are also used.54The diagnosis of SMA is confirmed based on the results of the MLPA assay using a newly-collected blood sample (Figure 2). Here, SMN1 is linked to proximal spinal muscular atrophy.