纤维蛋白原抗原比浊法（FIATA）：X2x检验——与对照均值的校正卡方比较。

Department of Clinical Chemistry, Central Laboratory, University Hospital, Marburg, Germany.

Clin Appl Thromb Hemost. 2007 Jan;13(1):73-100. doi: 10.1177/1076029606293436.

Vancomycin precipitates fibrinogen. The turbidity induced by this vancomycin-fibrinogen interaction is used to establish a simple standardized antigenic assay for plasmatic fibrinogen, the FIATA. 1 mM vancomycin or 2 mM chloramine-T inactivates 50% of fibrinogen in human plasma. In contrast to chloramine-T, vancomycin does not react in NaJ-based photometric assay for chloramines,vancomycin does not inactivate the singlet oxygen-sensible antithrombin III, and the vancomycin action against fibrinogen is not changed in spite of the presence of the 1O2 quenchers methionine or ascorbic acid. The FIATA is performed as follows: to 25 microL plasma 50 microL PBS are added and the absorbance (A) at 405 nm is read. Then 50 microL FIATA-reagent, consisting of 4.4 mM vancomycin in PBS, are added. After 2 minutes (RT) DeltaA is determined and standardized against a plasma pool of 100% of norm (2.8 g/L) fibrinogen. The FIATA is nearly linear up to a fibrinogen concentration of about 150% of norm (4.2 g/L), resulting in a DeltaA of about 600 mA. The lower detection limit is 4% of norm (0.1 g/L). The intra-assay and interessay CV values are < 4%. The normal range of FIATA is 100% +/-20% (x- +/- 1 SD). In = 321 or 344 unselected patient plasmas the FIATA (x- = 130%; SD = 52% or 43%) correlated with the functional fibrinogen assays a) modified Clauss-Method (x- = 4.1 g/L; SD =1.7 g/L) with r = 0.755 and b) FIFTA (x- = 124%; SD = 40%) with r = 0.813. The vancomycin/fibrinogen interaction (binding of about 16 molecules of vancomycin/molecule of fibrinogen) can be used to purify fibrinogen out of plasma. Vancomycin also clouds dysfunctional fibrinogen (fibrinogen in presence of EDTA or chloramine-T)or soluble fibrin. Vancomycin-reacted fibrinogen stimulates tissue type plasminogen activator (t-PA) up to about 20-fold. The experimental data are analyzed by a new significance test: the two foldYates-corrected chi-square comparison against the mean value ofthe control-collective, called the Chi2x - Test. The P < .05 significance barrier calculated with the Chi2x - Test is equivalent to that calculated with the Fisher's Exact Test. The FIATA might be considered an interesting screening test for inactive fibrinogen forms or soluble fibrin, as eg in disseminated intravascular coagulation. Fibrinogen precipitation by vancomycin within the blood vessel might explain why vancomycin has to be infused slowly (< 10 mg/min) to prevent nephrotoxicity. The FIATA is of such a simplicity that the determination of fibrinogen antigen in plasma can be performed anywhere--even outside a hospital--within seconds. Thus, the presented FIATA might contribute to extra hospital testing of patients for assessing their risk for myocardial or cerebral ischemia/infarction.

万古霉素可使纤维蛋白原沉淀。这种万古霉素 - 纤维蛋白原相互作用所诱导的浊度被用于建立一种简单的标准化抗原检测方法来检测血浆纤维蛋白原，即FIATA。1 mM万古霉素或2 mM氯胺 - T可使人体血浆中50%的纤维蛋白原失活。与氯胺 - T不同，万古霉素在基于NaJ的氯胺光度测定中不发生反应，万古霉素不会使对单线态氧敏感的抗凝血酶III失活，并且即使存在单线态氧淬灭剂甲硫氨酸或抗坏血酸，万古霉素对纤维蛋白原的作用也不会改变。FIATA的操作如下：向25微升血浆中加入50微升磷酸盐缓冲液（PBS），读取405 nm处的吸光度（A）。然后加入50微升由PBS中4.4 mM万古霉素组成的FIATA试剂。2分钟（室温）后测定吸光度变化量（ΔA），并以100%正常水平（2.8 g/L）纤维蛋白原的血浆池作为标准进行标准化。FIATA在纤维蛋白原浓度达到约正常水平的150%（4.2 g/L）之前几乎呈线性，此时ΔA约为600 mA。检测下限为正常水平的4%（0.1 g/L）。测定内和不同测定间的变异系数（CV）值均<4%。FIATA的正常范围是100%±20%（x - ±1标准差）。在321例或344例未选择的患者血浆中，FIATA（x - = 130%；标准差 = 52%或43%）与功能性纤维蛋白原检测方法相关：a）改良的Clauss法（x - = 4.1 g/L；标准差 = 1.7 g/L），相关系数r = 0.755；b）FIFTA（x - = 124%；标准差 = 40%），相关系数r = 0.813。万古霉素/纤维蛋白原相互作用（约每分子纤维蛋白原结合16分子万古霉素）可用于从血浆中纯化纤维蛋白原。万古霉素还会使功能异常的纤维蛋白原（存在乙二胺四乙酸（EDTA）或氯胺 - T时的纤维蛋白原）或可溶性纤维蛋白变浑浊。与万古霉素反应的纤维蛋白原可刺激组织型纤溶酶原激活剂（t - PA）高达约20倍。实验数据通过一种新的显著性检验进行分析：与对照群体平均值进行两倍耶茨校正卡方比较，称为Chi2x检验。用Chi2x检验计算出的P < 0.05显著性界限与用费舍尔精确检验计算出的结果相当。FIATA可被视为一种有趣的筛查试验，用于检测无活性纤维蛋白原形式或可溶性纤维蛋白，例如在弥散性血管内凝血中。血管内万古霉素引起的纤维蛋白原沉淀可能解释了为什么万古霉素必须缓慢输注（<10 mg/min）以预防肾毒性。FIATA非常简单，血浆中纤维蛋白原抗原的测定可以在任何地方——甚至在医院外——在几秒钟内完成。因此，所介绍的FIATA可能有助于在院外对患者进行检测，以评估他们发生心肌或脑缺血/梗死的风险。