Lorentz K
Institut für Klinische Chemie, Medizinische Universität Lübeck, D-23538 Lübeck, Germany.
Clin Chem. 2000 May;46(5):644-9.
In contrast to numerous methods for measuring alpha-amylase activity, the approved IFCC reference method offers an invariable time-independent constant product pattern, thus avoiding possibly changing stoichiometric calculations. However, reference methods do not lend themselves to routine use, so that such methods need to be modified.
Ethylidene-blocked 4-nitrophenylmaltoheptaoside (EPS-G7) is degraded to glucose and 4-nitrophenol in a coupled assay with a bacterial alpha-glucosidase under the following measurement conditions: 3.5 mmol/L EPS-G7, 7.1 kU/L alpha-glucosidase, 70 mmol/L sodium chloride, 1 mmol/L calcium chloride, 50 mmol/L HEPES, pH 7.15, at 37 degrees C. The increase of absorbance is continuously monitored for 3 min at 405 nm after a lag phase of 2 min.
Catalytic concentrations up to 15-fold higher than the upper reference limit can be determined without dilution. Precision studies in manual performance show CVs of 1.4-2. 6% (within-run) and 1.9-2.8% (day-to-day). There was no interference from 100 mmol/L glucose, 30 mmol/L triacylglycerols, 610 micromol/L bilirubin, and 2.95 g/L hemoglobin. The method closely correlates with other chromogenic assays. The preliminary 0.95 reference interval for adults, not dependent on age and sex, is 33.6-96.2 U/L.
The procedure is a robust adaptation of the reference method to routine use at 37 degrees C with increased sensitivity, fewer interferences, and reduced cost.
与众多测量α-淀粉酶活性的方法不同，已批准的国际临床化学和检验医学联合会（IFCC）参考方法提供了一种不变的、与时间无关的恒定产物模式，从而避免了可能变化的化学计量计算。然而，参考方法并不适用于常规使用，因此需要对其进行修改。
在以下测量条件下，亚乙基封闭的4-硝基苯基麦芽庚糖苷（EPS-G7）在与细菌α-葡萄糖苷酶的偶联测定中降解为葡萄糖和4-硝基苯酚：3.5 mmol/L EPS-G7、7.1 kU/L α-葡萄糖苷酶、70 mmol/L氯化钠、1 mmol/L氯化钙、50 mmol/L 4-(2-羟乙基)-1-哌嗪乙磺酸（HEPES），pH 7.15，37℃。在2分钟的延迟期后，在405 nm处连续监测吸光度增加3分钟。
无需稀释即可测定高达参考上限15倍的催化浓度。手工操作的精密度研究显示批内变异系数为1.4 - 2.6%，批间变异系数为1.9 - 2.8%。100 mmol/L葡萄糖、30 mmol/L三酰甘油、610 μmol/L胆红素和2.95 g/L血红蛋白均无干扰。该方法与其他比色法密切相关。成人初步的0.95参考区间（不依赖于年龄和性别）为33.6 - 96.2 U/L。
该程序是将参考方法稳健地应用于37℃的常规使用，具有更高的灵敏度、更少的干扰和更低的成本。
