Private equity investor Carlyle is in exclusive talks to buy Johnson & Johnson's ortho clinical diagnostics unit for around $4 billion, after knocking Blackstone out of the race, financial market reports said shortly before Christmas. A deal was expected to be concluded in the first half of January.

The unit, described as a small player in a market dominated by larger companies such as Roche, Siemens, Abbott and Danaher, manufactures blood-screening equipment and laboratory blood tests as well as tests capable of identifying blood types and screening for viruses such as HIV and hepatitis C.

At the beginning of 2013, Johnson & Johnson had said it was exploring strategic alternatives for business, a process that could take 12-24 months. Blackstone was reportedly bidding in cooperation with Danaher.