We also calculated the detection above background (DABG) metric for each probe set. After remapping the Affymetrix probe sets onto human genome build 19 (GRCh37) and using Netaffx annotation file Release 31 (HuEx-1_0-st-v2 Probeset Annotations), we restricted analysis to 291,705 exon-level probe sets that were annotated to have gene names according to NCBI Reference Sequence build 36 and contained at least three uniquely hybridizing probes that were free of the polymorphism-in-probe problem23 (SNP and indel frequency >1% according to the European panel 1000 Genomes Interim Phase v3, March 2012).
