Exhibit (a)(20) AMENDMENT NO. 4 TO AGREEMENT AND PLAN OF MERGER AMENDMENT NO. 4, dated as of January 4, 2003 (this "Amendment"), among QUEST DIAGNOSTICS INCORPORATED, a Delaware corporation ("Parent"), QUEST DIAGNOSTICS NEWCO INCORPORATED, a Delaware...Agreement and Plan of Merger • January 6th, 2003 • Quest Diagnostics Inc • Services-medical laboratories
