SMN1 and SMN2 Copy Number Determination by droplet digital PCR (ddPCR) based on Extreme Value Theory for Threshold Estimation

Spinal muscular atrophy (SMA) is the most frequent genetic cause of infantile death. Homozygous deletion screening of survival of motor neuron (SMN1) represents the first tier in diagnostic testing. In this work, we adopted and optimized a method to increase the accuracy of SMN1 and SMN2 copy number determination on ddPCR platform. This method, which makes no assumption about the distribution of the fluorescence readouts, was shown to significantly increase accuracy and outperform QuantaSoft software on problematic SMN1 samples. Method Summary In order to increase the accuracy of SMN1 and SMN2 copy number determination by ddPCR, we adopted and optimized a method based on extreme value theory for threshold estimation. Our method increases total accuracy and improves resolution of problematic samples.