U.S. medical-test giant Beckman Coulter Inc. has reached a deal to buy Biosite Inc. for 1.55 billion dollars, in a combination that will strengthen Beckman's presence in a specialized segment of the diagnostic-test market, The Wall Street Journal reported on Monday.

Beckman Coulter, based in Fullerton, California, was quoted as saying that it will acquire all of Biosite's outstanding stock in a cash tender offer of 85-dollar-a-share.

Beckman said it expects to launch the offer within about two weeks, pending regulatory filings. The companies said their respective boards have approved the transaction, according to the report.

Beckman's offer represents a 53-percent premium over Biosite's closing price Friday of 55.38 dollars in Nasdaq Stock Market composite trading.

Scott Garrett, Beckman president and chief executive, said the deal is "a great opportunity, even at a price that appears at first glance to be quite a high premium."