SOUTH SAN FRANCISCO, Calif., May 6, 2013 (GLOBE NEWSWIRE) -- diaDexus, Inc. (OTCQB:DDXS), a company developing and commercializing proprietary cardiovascular diagnostic products, today announced financial results for the first quarter ended March 31, 2013. Brian Ward, Ph.D., diaDexus' President and Chief Executive Officer, said, "diaDexus had a strong first quarter 2013, delivering our 11 th consecutive quarter of year-over-year revenue growth while making investments in our commercial operations and product development to support our long-term growth ambitions. These included the addition of new sales representatives in targeted geographies and increased focus on the development of our new product pipeline. We also continued to drive expanded reimbursement for the PLAC Test, which should help to reduce pricing pressure and have a positive impact on our cardiovascular specialty laboratory partners." Total revenues for the first quarter 2013 were $5.6 million, a 12% increase over $4.9 million reported in the first quarter 2012. Demand for the PLAC Test remained strong with volume increases outpacing pricing pressure. As a result, gross margins in the first quarter 2013 improved to 67% compared to 65% for the same quarter in 2012. Total operating expenses for the quarter were $6.9 million, compared to $6.2 million for the first quarter 2012. The increase in operating expenses was the result of increased investments in sales and marketing in the first quarter 2013 compared to the same quarter in 2012, partially offset by lower research and development costs. General and administrative expenses were flat in the first quarter 2013 compared to the same period in 2012. The Company's net loss for the first quarter 2013 narrowed to $1.2 million, or $(0.02) per share, from a net loss of $1.3 million, or $(0.02) per share, in the first quarter 2012. Cash and cash equivalents and investments at March 31, 2013 were $13.0 million compared to $13.6 million at December 31, 2012.