Gous N, Cunningham B, Kana B, Stevens W, Scott L E
Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
J Clin Microbiol. 2013 Dec;51(12):4018-21. doi: 10.1128/JCM.01715-13. Epub 2013 Sep 25.
The use of dried culture spots (DCSs) has been reported in the verification of GeneXpert instruments as being "fit for purpose" for the South African National implementation program. We investigated and compared the performance of the DCSs for verification across different bulk batches, testing the settings and cadre of staff, and the Xpert MTB/RIF assay version. Four bulk batches (V005 to V008) were used to prepare (i) 619 DCS panels for laboratory testing on G3 or G4 cartridges by a technologist, (ii) 13 DCS panels (batch V005) used for clinic verification on G3 cartridges by a nurse or lay counselor, and (iii) 20 DCS panels (batch V005) used for the verification of 10 GeneXpert 16 module instruments in mobile vehicles on the G3 cartridge performed by a scientist. The stabilities of the DCSs over 6 months at 4°C, room temperature, and 37°C were investigated. The mean cycle threshold (CT) and standard deviation (SD) for probe A were calculated. The proportions of variability in the CT values across bulk batches, assay versions, and settings and cadre of staff were determined using regression analysis. Overall, the DCSs demonstrated SDs of 3.3 (n = 660) for the G3 cartridges and 3.8 (n = 1,888) for the G4 cartridges, with an overall error rate of 1.5% and false rifampin resistance rate of 0.1%. The proportions of variability (R(2)) in the CT values explained by batch were 14%, by setting and cadre of staff, 5.6%, and by assay version, 4.2%. The most stable temperature in a period of up to 6 months was 37°C (SD, 2.7). The DCS is a robust product suitable for storage, transport, and use at room temperature for the verification of the GeneXpert instrument, and the testing can be performed by non-laboratory-trained personnel in nonlaboratory settings.
在南非国家实施计划中，已报道使用干培养斑点（DCS）对GeneXpert仪器进行验证，结果表明其“符合使用目的”。我们调查并比较了不同批量的DCS在验证方面的性能，测试了设置、工作人员类别以及Xpert MTB/RIF检测版本。使用了四个批量（V005至V008）来制备：（i）619个DCS板，供技术人员在G3或G4试剂盒上进行实验室检测；（ii）13个DCS板（V005批次），供护士或外行人顾问在G3试剂盒上进行临床验证；（iii）20个DCS板（V005批次），供科学家在移动车辆中对10台GeneXpert 16模块仪器在G3试剂盒上进行验证。研究了DCS在4°C、室温及37°C下6个月的稳定性。计算了探针A的平均循环阈值（CT）和标准差（SD）。使用回归分析确定了不同批量、检测版本以及设置和工作人员类别之间CT值的变异比例。总体而言，G3试剂盒的DCS标准差为3.3（n = 660），G4试剂盒为3.8（n = 1,888），总体错误率为1.5%，利福平耐药假阳性率为0.1%。由批次解释的CT值变异比例（R²）为14%，由设置和工作人员类别解释的为5.6%，由检测版本解释的为4.2%。长达6个月内最稳定的温度是37°C（SD，2.7）。DCS是一种坚固的产品，适合在室温下储存、运输和用于GeneXpert仪器的验证，且检测可由非实验室培训人员在非实验室环境中进行。
