RESUMEN
BACKGROUND: Macro-aspartate aminotransferase (macroAST) is a high molecular weight form of AST that is usually formed through association with immunoglobulin (Ig) in the circulation. As a result of reduced inactivation, clearance or excretion, AST values are persistently increased. This can lead to problems interpreting these values and diagnosing the patient, especially if clinicians are not aware of this phenomenon. METHODS: For a case of suspected macroAST, we compared three simple methods: polyethylene glycol precipitation, ultrafiltration, and Ig depletion using protein A and G. RESULTS: All three methods were consistent with a diagnosis of macroAST. CONCLUSIONS: The protein A and G method was straightforward and provided unambiguous results. However, given the affinity of protein A and protein G, it likely only detects AST-IgG macrocomplexes.