[Code of Federal Regulations] [Title 21, Volume 7] [Revised as of April 1, 2008] From the U.S. Government Printing Office via GPO Access [CITE: 21CFR660.44] [Page 128] TITLE 21--FOOD AND DRUGS CHAPTER I--FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) PART 660_ADDITIONAL STANDARDS FOR DIAGNOSTIC SUBSTANCES FOR LABORATORY TESTS-- Subpart E_Hepatitis B Surface Antigen Sec. 660.44 Specificity. Each filling of the product shall be specific for Hepatitis B Surface Antigen as determined by specificity tests found acceptable to the Director, Center for Biologics Evaluation and Research. [44 FR 36382, June 22, 1979, as amended at 49 FR 23834, June 8, 1984; 55 FR 11013, Mar. 26, 1990]