Private equity firm Carlyle Group has agreed to buy Johnson & Johnson's Ortho-Clinical Diagnostics medical testing unit for $4.15 billion, J&J announced Thursday. J&J said it will consult with works councils and trade unions over Carlyle's binding offer for OCD by the March 31 deadline. Carlyle said it plans additional investment in OCD, which it intends to run as an independent company. "Ortho-Clinical Diagnostics is an established global brand with a reputation for quality and innovation," said Carlyle Group managing director Stephen Wise in a statement. "Through accelerated investment in research and product development and continued expansion into both emerging and established markets, we expect to tap into rising demand for sophisticated medical diagnostic products and services worldwide." J&J announced a year ago that it was considering a sale of the unit, which had around $2 billion in revenues in 2012, to focus on other products that offer better growth prospects. J&J chief executive Alex Gorsky described the deal as resulting from "our disciplined approach to portfolio management in order to achieve the greatest value for Johnson & Johnson." OCD, with manufacturing facilities in the US and Wales, provides in-vitro diagnostic products that conduct screening and blood-typing to diagnose diseases and ensure transfusion patients receive the right type of blood. The company also provides information management, testing technologies and automation tools to clinical laboratories. J&J said if it accepts the Carlyle offer, it expects the transaction to close toward the middle of the year pending regulatory approval. J&J was down 0.2 percent to $94.62 in midday trade, and Carlyle lost 0.1 percent to $36.94.