Exhibit 16.1 Eisner LLP 750 Third Avenue New York, NY 10017 November 19, 2004 Dear Mr. Kaiser: The letter shall confirm that the engagement of your firm is terminated. This termination and the engagement of Marcum & Kliegman, LLP as our new independent auditors were approved by our full Board of Directors. Your firm is hereby authorized to respond fully to the inquiries of Marcum & Kliegman, LLP. Our counsel will be preparing the Form 8-K which will be due November 25, 2004. You will be provided with a copy of the disclosures that we will be making in response to Item 304(a) of Regulation S-B. Please furnish us with a letter addressed to the Securities and Exchange Commission as to whether you agree with the statements made by us herein. Very truly yours, UNITED DIAGNOSTIC, INC. By: /s/ J. Marvin Feigenbaum ----------------------------------------- Name: J. Marvin Feigenbaum Title: Chairman and President