title: Evaluation of a direct alpha-amylase assay using 2-chloro-4-nitrophenyl-alpha-D-maltotrioside.
abstract: We present the adaptation of an IFCC method for alpha-amylase using 2-chloro-4-nitro-phenyl-alpha-D-maltotrio-side as substrate (1) suited for routine work at 37 degrees C. In the assay, a constant proportion of substrate, i. e. 92%, is directly converted to 2-chloro-4-nitrophenol and maltotriose. The method is based on multi- and univariate optimization leading to following measurement conditions: substrate, 2.25 mmol/l; chloride, 310 mmol/l; calcium 5.0 mmol/l; 4-morpholinoethanesulphonic acid, 50 mmol/l; pH 6.28. The assay may be carried out manually or by mechanized procedures, with substrate or sample start, and it shows these analytical properties in measuring amylase activity of sera: no lag phase, detection limit 2.9 U/l, linear range < or = 820 U/l (for 300 s) or < or = 1450 U/l (for 120 s of measurement), and total manual imprecision 3.2% (CV) at 46 U/l. Bilirubin < or = 630 micromol/l, haemoglobin < or =6 g/l, triacylglycerols < or =30 mmol/l, heparin < or =100 kU/l, and glucose < or =120 mmol/l do not interfere. For adults, we established a preliminary 0.95-reference interval of 30-90 U/l not dependent on sex or age. A close association with the IFCC method demonstrates the reliable transfer of its measurement conditions to a robust routine method with minimal changes.
authors.affiliation: Institut für Klinische Chemie, Medizinische Universität Lübeck, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Lorentz
authors.forename: B
authors.initials: B
authors.lastname: Gütschow
authors.forename: F
authors.initials: F
authors.lastname: Renner
mesh_terms: D000328:Adult; D005069:Evaluation Studies as Topic; D006801:Humans; D007700:Kinetics; D015203:Reproducibility of Results; D013057:Spectrum Analysis; D014312:Trisaccharides / Q000737:chemistry*; D000516:alpha-Amylases / Q000032:analysis* / Q000378:metabolism
chemical_list: D014312:Trisaccharides; C057413:2-chloro-4-nitrophenylmaltotrioside; D000516:alpha-Amylases