Chong S, Jang D, Song X, Mahony J, Petrich A, Barriga P, Chernesky M
McMaster University and Father Sean O'Sullivan Research Centre, St Joseph's Healthcare, Hamilton, Ontario, Canada.
J Clin Microbiol. 2003 Feb;41(2):778-82. doi: 10.1128/JCM.41.2.778-782.2003.
Inhibitors in clinical specimens can be detected by adding the target of nucleic acid amplification to the sample. Introduction of a Chlamydia trachomatis L2 434 preparation containing 12 elementary bodies (EBs) into first-void urine (FVU) from 225 nonpregnant women and 190 pregnant women before specimen processing by the assays produced false-negative rates of 0.48% (2 of 415 specimens) and 13% (44 of 338 specimens) by the APTIMA Combo 2 and the Chlamydia LCx tests, respectively. Reducing the amount of C. trachomatis added to one EB, a concentration closer to the APTIMA Combo 2 test cutoff, for a subset of 244 FVU specimens increased the number of specimens with false-negative results by the APTIMA Combo 2 assay to 7 (2.9%), suggesting that the strength of the input C. trachomatis per specimen has an influence on the number of specimens with false-negative results. Repeat testing after overnight storage and dilution decreased the APTIMA Combo 2 test false-negative rates to 0% (0 of 415 specimens) with the stronger inoculum and 0.8% (2 of 244 specimens) with the weaker inoculum; the false-negative rate of the LCx assay was reduced to 5.4% (18 of 334 specimens). When an additional 70 FVU specimens from women to which 12 EBs were added before specimen processing were tested by the LCx assay, 34 specimens had false-negative results, whereas 21 specimens had false-negative results when the C. trachomatis EBs were introduced after processing. Nine of the 21 specimens to which EBs were added after processing and all of the 34 urine specimens to which the target was added before processing remained falsely negative on repeat testing at a 1:2 dilution, suggesting that input C. trachomatis DNA was lost during processing by the LCx assay. In contrast, the APTIMA Combo 2 assay appears to have a higher sensitivity and either lost little nucleic acid during processing or demonstrated few problems with inhibitors of transcription-mediated amplification.
通过向样本中添加核酸扩增靶标，可以检测临床样本中的抑制剂。在通过检测方法处理样本之前，将含有12个原体（EB）的沙眼衣原体L2 434制剂加入225名非孕妇和190名孕妇的首次晨尿（FVU）中，APTIMA Combo 2检测和衣原体LCx检测产生的假阴性率分别为0.48%（415份样本中的2份）和13%（338份样本中的44份）。对于244份FVU样本的一个子集，将添加的沙眼衣原体数量减少到一个EB，该浓度更接近APTIMA Combo 2检测的临界值，这使得APTIMA Combo 2检测出现假阴性结果的样本数量增加到7份（2.9%），表明每个样本中输入的沙眼衣原体强度对出现假阴性结果的样本数量有影响。过夜储存和稀释后重复检测，对于接种量较大的样本，APTIMA Combo 2检测的假阴性率降至0%（415份样本中的0份），对于接种量较小的样本，假阴性率降至0.8%（244份样本中的2份）；LCx检测的假阴性率降至5.4%（334份样本中的18份）。当对另外70份在样本处理前添加了12个EB的女性FVU样本进行LCx检测时，34份样本出现假阴性结果，而在处理后引入沙眼衣原体EB时，有21份样本出现假阴性结果。在处理后添加EB的21份样本中有9份以及在处理前添加靶标的所有34份尿液样本在1:2稀释重复检测时仍为假阴性，这表明在LCx检测处理过程中输入的沙眼衣原体DNA丢失了。相比之下，APTIMA Combo 2检测似乎具有更高的灵敏度，并且在处理过程中几乎没有核酸丢失，或者在转录介导的扩增抑制剂方面几乎没有问题。
