Mergermarket, a mergers and acquisitions tracking service, said TPG Capital and Bain Capital were among the few private equity firms that have the wherewithal to join hands to make a run at the lab-testing company which has a market capitalization of $8.1 billion.

Other potential players who may become involved in the deal are Blackstone Group, Kohlberg Kravis Roberts, and Madison Dearborn, the website quoted the sources as saying.

The company's sheer size would make a leveraged buyout a tall order and equity financing alone could make a buyout difficult as an equity check of $3 billion to $4 billion is expected for the deal, the sources told Mergermarket.

BofA Merrill Lynch is heading efforts to raise capital for the buyout and might partner with other banks to underwrite deal, the site said.

None of the private equity parties named in the Mergermarket report were immediately available for comment.

LabCorp was also not available for comment.

LabCorp shares were up about 6 percent in after-market trade on Tuesday on the New York Stock Exchange. They had closed at $84.09.

(Reporting by Eileen Anupa Soreng and Himank Sharma in Bangalore; Editing by Edwina Gibbs)

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