Isolated elevated aspartate aminotransferase in an asymptomatic woman due to macro-aspartate aminotransferase: A case report

Abstract

BACKGROUNDMacro-aspartate aminotransferase (AST), a macroenzyme, is a high-molecular mass complex formed by self-polymerization or association with other serum components that are difficult for the kidney to clear, leading to the isolated elevation of serum AST activity. Cases of macro-AST formation are rare, with only 3 published in the English language literature up to September 2019 in China. In this paper, we present a case in which an asymptomatic woman with persistent isolated elevated AST was confirmed as having macro-AST by the polyethylene glycol precipitation method.CASE SUMMARYA 34-year-old woman was referred to our clinic for elevated AST levels with normal levels of other liver-associated enzymes on November 12, 2018. Her AST level of liver function test had been abnormal for 7 mo before she came to the clinic. The patient was asymptomatic with a normal physical examination. There was no relevant family history and no alcohol consumption or smoking. She had a several-month history of traditional Chinese medical taking and had stopped it 1 year prior. The laboratory tests in our clinic showed only the elevation of AST (89.5 U/L) with no other significant abnormalities. We performed the precipitation technique with polyethylene glycol to confirm the presence of macro-AST. Then for almost a year, her AST level still fluctuated in the abnormal range.CONCLUSIONThis case highlights that clinical physicians should be familiar with this rare condition of persistent isolated AST elevation due to the presence of macro-AST to avoid unnecessary investigation and patient anxiety.

Macro-aspartate aminotransferase in a healthy woman

“…1 Ultracentrifugation and gel filtration chromatography, which constitute the standard reference method, require highly specialised chromatography, are complex, relatively expensive, and time-consuming and are not available in most clinical laboratories. 8 Electrophoresis for immunofixation with AST staining consists of the electrophoresis of serum proteins using the IgG, IgA and IgM antisera. It allows the nature of enzyme immune complexes to be clarified, but requires high specialisation skills.…”

“…and there is heterogeneity of the macroAST molecule due to the different types of Ig or other plasma components. 8 Finally, the PEG precipitation, described above, unlike the latter more complicated techniques, is a simple and low-cost method, which is commonly used for the detection of macroprolactin, 5 possible in most routine laboratories and can be used for the screening of mac-roAST, giving a diagnosis in a short period of time. This method, however, has some limitations, like the possibility of interference with some assays, low specificity and the fact that an increase in serum globulins can lead to false positive results, as shown for macroprolactin.…”

“…It is performed using centrifugal filter units with membranes, and AST activity is measured in the ultracentrifugate after centrifugation for 18 hours [ 1 ]. Ultracentrifugation and gel filtration chromatography, which constitute the standard reference method, require highly specialised chromatography, are complex, relatively expensive, and time-consuming and are not available in most clinical laboratories [ 8 ]. Electrophoresis for immunofixation with AST staining consists of the electrophoresis of serum proteins using the IgG, IgA and IgM antisera.…”

“…Moreover, refrigerated sample storage for 3–6 days at 4°C determines the gradual precipitation of the enzyme-Ig complex. This method is simple and reliable, but it is performed over a long time and there is heterogeneity of the macroAST molecule due to the different types of Ig or other plasma components [ 8 ]. Finally, the PEG precipitation, described above, unlike the latter more complicated techniques, is a simple and low-cost method, which is commonly used for the detection of macroprolactin [ 5 ], possible in most routine laboratories and can be used for the screening of macroAST, giving a diagnosis in a short period of time.…”

Macro-Aspartate Aminotransferase

“…Литературные данные о пациентах с доказанной макро-АсАТ с помощью ПЭГ-преципитации или других информативных методов преимущественно представлены описаниями отдельных или небольших серий случаев [1,3,7,9,11,13,[16][17][18][19][20][21][22][23]. Имеется описание случая семейной ма-кро-АсАТ [24].…”