Budd R, Harley E, Quarshie A, Henderson V, Harris E N, Pierangeli S S
ELISA Department, The Binding Site Ltd, Birmingham, UK.
J Thromb Haemost. 2006 Oct;4(10):2210-4. doi: 10.1111/j.1538-7836.2006.02134.x. Epub 2006 Jul 20.
Recent reports show an apparent large number of individuals with low to moderate titers of anticardiolipin antibodies (ACA), particularly of the IgM isotype with no clinical signs of antiphospholipid syndrome (APS). The significance of these results is unknown. This study examined the prevalence of low positive titers of IgM ACA antibodies in a large number (n = 982) of normal blood donors (Group 1) and in a group of 159 individuals > 60 years of age (Group 2). The effect of re-defining the currently used cut-off values for the IgM ACA tests was also examined.
IgM ACA antibodies were tested in three ELISA assays: the Bindazyme Anti-IgM Cardiolipin EIA kit (assay A), an 'in-house' ACA test (assay B), and the APhL ELISA kit (assay C).
THE normal range cut-offs were re-calculated using the 95th percentile of the data for Group 1 (12.4 MPL U mL(-1) for assay A, 5.4 MPL U mL(-1) for assay B and 9.5 MPL U mL(-1) for assay C) and Group 2 (9.9 MPL U mL(-1) for assay A, 5.5 MPL U mL(-1) for assay B and 13.2 MPL U mL(-1) for assay C). These values were not significantly different from the current cut-off values for each assay. The prevalence of low positive results in Group 1 relative to the re-defined cut-off for that group were: 1.0%, 1.1% and 0.9% in assay A, B and C; and in Group 2: 0.6%, 0.6% and 0.6%, respectively. An indeterminate zone (between the 95th and 99th percentile) was then established for the two groups. The prevalence in Group 1 was 3.8%, 3.9% and 3.9% for assays A, B and C, respectively, and for Group 2: 4.4% in all three assays.
The data confirm that the current cut-off point for each of the three assays is correct. We suggest based on this study that the low positive range is re-assigned 'indeterminate' and recommend that samples falling in this category should be retested to confirm positivity at a later date.
近期报告显示，有相当数量的个体抗心磷脂抗体（ACA）滴度低至中等，尤其是IgM同种型，且无抗磷脂综合征（APS）的临床症状。这些结果的意义尚不清楚。本研究调查了大量（n = 982）正常献血者（第1组）和159名60岁以上个体（第2组）中IgM ACA抗体低阳性滴度的患病率。还研究了重新定义当前IgM ACA检测临界值的影响。
采用三种酶联免疫吸附测定（ELISA）检测IgM ACA抗体：Bindazyme抗IgM心磷脂酶免疫分析试剂盒（检测A）、一种“内部”ACA检测（检测B）和APhL ELISA试剂盒（检测C）。
使用第1组数据的第95百分位数重新计算正常范围临界值（检测A为12.4 MPL U mL⁻¹，检测B为5.4 MPL U mL⁻¹，检测C为9.5 MPL U mL⁻¹）以及第2组数据的第95百分位数（检测A为9.9 MPL U mL⁻¹，检测B为5.5 MPL U mL⁻¹，检测C为13.2 MPL U mL⁻¹）。这些值与各检测当前的临界值无显著差异。第1组相对于该组重新定义的临界值，低阳性结果的患病率在检测A、B、C中分别为1.0%、1.1%和0.9%；在第2组中分别为0.6%、0.6%和0.6%。然后为两组确定了一个不确定区间（第95百分位数和第99百分位数之间）。第1组在检测A、B、C中的患病率分别为3.8%、3.9%和3.9%，第2组在所有三种检测中的患病率均为4.4%。
数据证实三种检测各自当前的临界值是正确的。基于本研究，我们建议将低阳性范围重新归类为“不确定”，并建议对属于该类别的样本进行重新检测，以便日后确认阳性结果。
