SPOKANE, Wash.--(BUSINESS WIRE)--Inc. magazine ranked Signature Genomic Laboratories no. 1012 on its third annual Inc. 5000, an exclusive ranking of the nation’s fastest-growing private companies. The company, which performs microarray-based diagnostic genetic testing of chromosome abnormalities in individuals with unexplained mental retardation and/or birth defects, experienced three-year sales growth of 302.9%, more than twice that of the Inc. 5000 industry median and over 12 times the industry benchmark. Signature was also ranked 70th of companies in the healthcare sector.