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Shiro Ono,1 Chikara Kurata,2 Nobushiro Nishimura,1 Hiromasa Kawashima,1 Ryo Yoneima,1 Yoshiaki Tai,1 Emiko Tatsumi,1 Makiko Miyamoto,1 Noritaka Yada,1 Kiyomi Yoshimoto,1 Kenji Nishio1 1Department of General Medicine, Nara Medical University, Nara, Japan; 2Department of Clinical Laboratory, Nara Medical University, Nara, JapanCorrespondence: Kenji NishioDepartment of General Medicine, Nara Medical University, 840 Shijo-Cho, Kashihara City, Nara 634-8522, JapanTel +81-744-29-8905Fax +81-744-24-5739Email knishio@naramed-u.ac.jpAbstract: The macroenzyme form of aspartate aminotransferase (macro-AST) is formed by the binding of AST with immunoglobulins. Macro-AST excretion from serum is prolonged because of its high molecular weight, leading to increased AST activities. Because of the difficulty in detecting macro-AST through routine laboratory tests, affected patients often undergo repeated examinations, with associated anxiety. We report a case in which macro-AST was detected by assaying the patient’s serum after refrigeration at 4ºC for 3 days. The sample showed progressive loss of AST activity compared with that frozen in the refrigerator, indicating the presence of macro-AST, which was confirmed as a complex with IgG-κ. The cold storage method was validated using many samples obtained from several patients. Use of this simple method to detect macro-AST may avoid unnecessary examinations and patient anxiety even at primary care facilities.Keywords: isolated elevation of aspartate aminotransferase, macroenzyme, macro-AST, cold storage method |
