Mahony J, Chong S, Jang D, Luinstra K, Faught M, Dalby D, Sellors J, Chernesky M
Regional Virology and Chlamydiology Laboratory, Hamilton, Ontario, Canada.
J Clin Microbiol. 1998 Nov;36(11):3122-6. doi: 10.1128/JCM.36.11.3122-3126.1998.
The presence of endogenous amplification inhibitors in urine may produce false-negative results for the detection of Chlamydia trachomatis nucleic acids by tests such as PCR, ligase chain reaction (LCR), and transcription-mediated amplification (TMA). Consecutive urine specimens from 101 pregnant women and 287 nonpregnant women submitted for urinalysis were processed for C. trachomatis detection. Aliquots were spiked with the equivalent of one C. trachomatis elementary body and were tested by three commercial assays: AMPLICOR CT/NG, Chlamydia LCX, and Chlamydia TMA. The prevalence of inhibitors resulting in complete inhibition of amplification was 4.9% for PCR, 2.6% for LCR, and 7.5% for TMA. In addition, all three assays were partially inhibited by additional urine specimens. Only PCR was more often inhibited by urine from pregnant women than by urine from nonpregnant women (9.9 versus 3.1%; P = 0.011). A complete urinalysis including dipstick and a microscopic examination was performed. Logistic regression analysis revealed that the following substances were associated with amplification inhibition: beta-human chorionic gonadotropin (odds ratio [OR], 3.3) and crystals (OR, 3.3) for PCR, nitrites for LCR (OR, 14.4), and hemoglobin (OR, 3.3), nitrites (OR, 3.3), and crystals (OR, 3.3) for TMA. Aliquots of each inhibitory urine specimen were stored at 4 and -70 degreesC overnight or were extracted with phenol-chloroform and then retested at dilutions of 1:1, 1:4, and 1:10. Most inhibition was removed by storage overnight at 4 or -70 degreesC and a dilution of 1:10 (84% for PCR, 100% for LCR, and 92% for TMA). Five urine specimens (three for PCR and two for TMA) required phenol-chloroform extraction to remove inhibitors. The results indicate that the prevalence of nucleic acid amplification inhibitors in female urine is different for each technology, that this prevalence may be predicted by the presence of urinary factors, and that storage and dilution remove most of the inhibitors.
尿液中内源性扩增抑制剂的存在可能会导致通过PCR、连接酶链反应（LCR）和转录介导扩增（TMA）等检测沙眼衣原体核酸时出现假阴性结果。对101名孕妇和287名非孕妇提交进行尿液分析的连续尿液标本进行处理，以检测沙眼衣原体。将等分试样加入相当于一个沙眼衣原体原体的量，并通过三种商业检测方法进行检测：AMPLICOR CT/NG、衣原体LCX和衣原体TMA。导致扩增完全抑制的抑制剂的发生率，PCR为4.9%，LCR为2.6%，TMA为7.5%。此外，所有三种检测方法都受到其他尿液标本的部分抑制。只有PCR受孕妇尿液抑制的情况比非孕妇尿液更常见（9.9%对3.1%；P = 0.011）。进行了包括试条检测和显微镜检查在内的完整尿液分析。逻辑回归分析显示，以下物质与扩增抑制有关：PCR的β-人绒毛膜促性腺激素（优势比[OR]，3.3）和晶体（OR，3.3），LCR的亚硝酸盐（OR，14.4），以及TMA的血红蛋白（OR，3.3）、亚硝酸盐（OR，3.3）和晶体（OR，3.3）。每个抑制性尿液标本的等分试样在4℃和-70℃下储存过夜，或用酚-氯仿提取，然后以1:1、1:4和1:10的稀释度重新检测。通过在4℃或-70℃下储存过夜和1:10的稀释度，大多数抑制作用被消除（PCR为84%，LCR为100%，TMA为92%）。五个尿液标本（三个用于PCR，两个用于TMA）需要酚-氯仿提取以去除抑制剂。结果表明，女性尿液中核酸扩增抑制剂的发生率因每种技术而异，这种发生率可能由尿液因素的存在来预测，并且储存和稀释可以去除大多数抑制剂。
