Rubin AS, Sass DA, Stickle DF. Distribution of serum concentrations reported for macroenzyme aspartate aminotransferase (macro-AST).
Pract Lab Med 2017;
8:65-69. [PMID:
28856230 PMCID:
PMC5575363 DOI:
10.1016/j.plabm.2017.05.003]
[Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2017] [Revised: 04/12/2017] [Accepted: 05/15/2017] [Indexed: 11/30/2022] Open
Abstract
Background
The presence of macroenzyme (M) is often the explanation of an isolated elevation of aspartate aminotransferase (AST). Where M is identified, it is reasonable for the clinician to ask where an individual patient's result fits in with known concentrations of M. In this context, we conducted a survey of literature to examine the distribution of reported serum concentrations of macro-AST. We also analyzed the distribution data to examine whether elevations were consistent with simple alteration of circulatory half-life (t1/2) of M relative to normal AST.
Methods
Distributions of M were compiled from the literature. These distributions were compared to predictions based on fixed changes in t1/2 applied to the reference interval for AST.
Results
There was a bimodal distribution of literature values for M (n =51), comprised roughly of populations A (M <200 U/L; 60% of total) and B (M >200 U/L; 40% of total). The two distributions were reasonably well characterized by a simple projection to the right of the reference interval for AST according to increased t1/2 (A: t1/2 =3.3 days; B: t1/2 =19.8 days) relative to AST (t1/2 =0.7 days).
Conclusions
Knowledge of distributions for M may be useful in discussion with clinicians regarding significance of M for individual patients. Distributions for M were consistent with the simplest explanation for elevated AST due strictly to an extended circulatory lifetime for M. Caveats to analysis, however, include selection within literature data mainly for patients with various co-morbidities.
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