title: Letter: Decrease of HB-s Ag titers after repeated freezing and thawing.
mesh_terms: D001793:Blood Preservation; D005615:Freezing; D006511:Hepatitis B Antigens / Q000302:isolation & purification*; D006801:Humans; D011863:Radioimmunoassay; D013696:Temperature
chemical_list: D006511:Hepatitis B Antigens