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.
Phototherapy converts lipophilic unconjugated bilirubin to hydrophilic bilirubin photoisomers, such as lumirubin. We comparatively used a blue light-emitting diode (LED) and a green fluorescent lamp (FL) as light sources for phototherapy of hyperbilirubinemic preterm neonates with the aim of examining potential differences in urinary lumirubin excretion between these two wavelengths. Urinary lumirubin levels were measured using a fluorescence assay with blue light exposure in the presence of the unconjugated bilirubin-inducible fluorescent protein UnaG, and denoted as urinary UnaG-bound bilirubin (UUB)/creatinine (Cr) (µg/mg Cr). Preterm neonates born at ≤ 33 weeks gestational age and treated with phototherapy were subjected to this study. The maximum UUB/Cr level during phototherapy per device intensity was compared between neonates treated with the blue LED and the green FL. A total of 61 neonates were examined to determine the maximum UUB/Cr levels. The median of maximum UUB/Cr excretion per light intensity of each device (µg/mg Cr/µW/cm2/nm) was 0.21 for the blue LED and 0.32 for the green FL (p = 0.01). Green light was found to be more effective than blue one for bilirubin excretion via urinary lumirubin excretion. This is the first spectroscopic study to compare the efficacy of phototherapy at different wavelengths using fluorescence assay.
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