Johnson Gemma L, Sarker Shah-Jalal, Hill Kate, Tsitsikas Dimitris A, Morin Amelie, Bustin Stephen A, Agrawal Samir G
Blizard Institute of Cell and Molecular Science, Queen Mary University of London, London E1 2AT, UK.
Int J Mol Sci. 2013 Jun 24;14(7):12970-7. doi: 10.3390/ijms140712970.
Galactomannan (GM) is widely used for detection of invasive aspergillosis in high-risk haemato-oncology patients. Recent publications have reported a lack of repeatability of GM detection. The objective of this retrospective study was to assess the repeatability of GM levels during storage of clinical samples. In a GM screening strategy, positive sera were repeat tested as per manufacturer's recommendations. Short-term (ST) storage of samples was at +4 °C while long-term (LT) storage was at -80 °C. Bronchoalveolar (BAL) fluid was also repeating tested after ST storage and LT storage. Wilcoxon Signed Ranks Test was employed to assess the repeatability of GM levels. In a subset of 14 GM positive sera, repeat testing was performed on both the original serum and ethylenediaminetetraacetic acid (EDTA) pre-treated sample. There was a significant reduction in GM signals on repeat testing following ST storage (median GM index: 0.65 vs. 0.19; p < 0.001) and LT storage (median GM index: 0.56 vs. 0.10; p < 0.001) of serum samples. Of samples that were initially GM positive, an average GM index reduction of 50% was seen, with approximately two-thirds becoming GM negative on repeat testing of the same sample. In contrast, GM signal loss was not seen on repeat testing of BAL fluid following ST or LT storage. When GM positive serum samples were repeat tested using EDTA pre-treated serum from the first step of the testing protocol, all samples remained GM positive. In contrast, when the same samples were repeat tested from the original collected serum, 9 samples (64%) became GM negative. The significant reduction in GM signals during ST and LT storage of serum samples has implications for clinical management. Although the reasons for GM decline are unknown, they occur prior to the EDTA pre-treatment stage, indicating that the time from phlebotomy to testing should be minimized. BAL fluid GM index values remain stable.
半乳甘露聚糖（GM）广泛用于检测高危血液肿瘤患者的侵袭性曲霉病。近期的出版物报道了GM检测缺乏可重复性。这项回顾性研究的目的是评估临床样本储存期间GM水平的可重复性。在GM筛查策略中，按照制造商的建议对阳性血清进行重复检测。样本短期（ST）储存在4℃，长期（LT）储存在-80℃。支气管肺泡灌洗（BAL）液在ST储存和LT储存后也进行重复检测。采用Wilcoxon符号秩检验评估GM水平的可重复性。在14份GM阳性血清的子集中，对原始血清和乙二胺四乙酸（EDTA）预处理样本均进行了重复检测。血清样本在ST储存（GM指数中位数：0.65对0.19；p<0.001）和LT储存（GM指数中位数：0.56对0.10；p<0.001）后重复检测时，GM信号显著降低。最初GM阳性的样本中，平均GM指数降低了50%，同一样本重复检测时约三分之二变为GM阴性。相比之下，BAL液在ST或LT储存后重复检测未发现GM信号丢失。当使用检测方案第一步中的EDTA预处理血清对GM阳性血清样本进行重复检测时，所有样本仍为GM阳性。相反，当从原始采集的血清中对相同样本进行重复检测时，9份样本（64%）变为GM阴性。血清样本在ST和LT储存期间GM信号的显著降低对临床管理有影响。尽管GM下降的原因尚不清楚，但它们发生在EDTA预处理阶段之前，这表明应尽量缩短从采血到检测的时间。BAL液GM指数值保持稳定。
