WARBURG PINCUS STARTS SYMBION <SYMB> BID <Warburg, Pincus Capital Corp> said it has started a tender offer for up to 2,500,000 common shares of Symbion Inc at 3.50 dlrs each. In a newspaper advertisement, The firm said the opffer is not conditioned on receipt of any minimum number of shares but is conditioned on holders of nor more than 400,000 Symbion sharesseeking to receive the fair value of their shares under provisions of the Utah Business Corporation Act. Warburg said receipt of 2,500,000 shares would raise its interest in Symbion to about 59.3 pct from 25.8 pct currently and give it control. Warburg said it reserves the right to buy more than 2,500,000 shares if the offer is oversubscribed but has no present intention of doing so. It said it has asked Symbion to provide its shareholder list to help in disseminating the offer. The firm said the offer, proration period and withdrawal rights expire April 22 unless extended.