Quest Diagnostics ( DGX) said it would sell $900 million worth of senior notes in a private placement to complete its acquisition of LabOne ( LABS). The Lyndhurst, N.J., lab company said the notes will be guaranteed on a senior, unsecured basis by its domestic clinical laboratories. The company has agreed to exchange these private notes for publicly tradable notes having substantially identical terms, and will file a registration statement with the Securities and Exchange Commission. The company expects the offering will be completed by Oct. 31. On Tuesday, Quest fell 13 cents to $46.55 and LabOne was flat at $43.85.