Department of Paediatric Haematology, Erasmus University Medical Centre - Sophia Children's Hospital Rotterdam, Rotterdam, The Netherlands.
ECAT foundation, Voorschoten, The Netherlands.
Haemophilia. 2019 Jan;25(1):162-169. doi: 10.1111/hae.13643. Epub 2018 Nov 29.
Both one-stage (OSA) and chromogenic substrate assays (CSA) are used to measure factor VIII (FVIII) activity. Factors explaining analytical variation in FVIII activity levels are still to be completely elucidated.
The aim of this study was to investigate and quantify the analytical variation in OSA and CSA.
Factors determining analytical variation were studied in sixteen lyophilized plasma samples (FVIII activity <0.01-1.94 IU/mL) and distributed by the ECAT surveys. To elucidate the causes of OSA variation, we exchanged deficient plasma between three company set-ups.
On average, 206 (range 164-230) laboratories used the OSA to measure FVIII activity and 30 (range 12-51) used CSA. The coefficient of variation of OSA and CSA increased with lower FVIII levels (FVIII <0.05 IU/mL). This resulted in misclassification of a severe haemophilia A sample into a moderate or mild haemophilia A sample in 4/30 (13.3%) of CSA measurements, while this was 37/139 (26.6%) for OSA. OSA measurements performed with reagents and equipment from Werfen showed slightly lower FVIII activity (0.93, IQR 0.88-0.98 IU/mL) compared to measurements with Stago (1.07, IQR 1.02-1.14 IU/mL) and Siemens (1.03, IQR 0.97-1.07 IU/mL). Part of this difference is explained by the value of the calibrator. For CSA, the measured FVIII levels were similar using the different kits.
In the lower range (<0.05 IU/mL), analytical variation of FVIII measurements is high in both OSA and CSA measurements. The variation in FVIII activity levels was partly explained by specific manufacturers. Further standardization of FVIII measurements and understanding of analytical variation is required.
一步法（OSA）和显色底物法（CSA）都被用于测量VIII 因子（FVIII）活性。但仍有一些因素会影响 FVIII 活性水平的分析变异，这些因素尚未完全阐明。
本研究旨在调查和量化 OSA 和 CSA 的分析变异。
我们研究了十六个冻干血浆样本（FVIII 活性<0.01-1.94 IU/mL）中的分析变异决定因素，并通过 ECAT 调查进行了分配。为了阐明 OSA 变异的原因，我们在三个公司的设置之间交换了缺陷血浆。
平均而言，有 206 个（范围 164-230）实验室使用 OSA 来测量 FVIII 活性，有 30 个（范围 12-51）实验室使用 CSA。OSA 和 CSA 的变异系数随着 FVIII 水平的降低而增加（FVIII<0.05 IU/mL）。这导致在 30 个 CSA 测量中，有 4 个（13.3%）严重血友病 A 样本被错误分类为中度或轻度血友病 A 样本，而在 139 个 OSA 测量中，有 37 个（26.6%）被错误分类。与使用 Stago（1.07，IQR 1.02-1.14 IU/mL）和 Siemens（1.03，IQR 0.97-1.07 IU/mL）的试剂和设备相比，使用 Werfen 试剂和设备进行的 OSA 测量显示出稍低的 FVIII 活性（0.93，IQR 0.88-0.98 IU/mL）。这种差异的一部分可以用校准品的值来解释。对于 CSA，使用不同试剂盒测量的 FVIII 水平相似。
在较低的范围内（<0.05 IU/mL），OSA 和 CSA 测量的 FVIII 测量的分析变异都很高。FVIII 活性水平的变异部分可以用特定的制造商来解释。需要进一步对 FVIII 测量进行标准化并更好地理解分析变异。
