St Mary's Hospital Center, Montreal, Quebec.
Can J Infect Dis Med Microbiol. 2011 Summer;22(2):e12-5. doi: 10.1155/2011/591239.
The recent increase in Clostridium difficile-associated diarrhea (CDAD) has led to questions about the reproducibility and sensitivity of C difficile toxin testing (CDTT). While there have been recommendations to repeat CDTT following a negative result, previous studies have failed to show a benefit. However, no studies were performed during an outbreak of CDAD. The value of repeat CDTT after an initial negative result in patients tested during and after an outbreak of CDAD is reported in the present study, as well as the reproducibility of CDTT when multiple samples are received and tested on the same day.
The results of CDTT, performed using a cell cytotoxicity assay between April 1, 2001, and March 31, 2008, were retrieved and searched for patients who had repeat samples tested after an initial negative result. The result and the number of days after a negative result were determined using the date of the most recent negative test. The cumulative positivity rate was calculated by adding all of the repeat positive test results for the days in question and dividing by the total number of tests performed during that time.
A total of 8661 patients submitted 14,991 stool specimens for CDTT during the study period. There were 3095 samples that tested positive (20.6%) for the toxin. The results were divided into two time periods to reflect the CDAD outbreak, which began in April 2002: period 1 (outbreak) was from April 1, 2002, to March 31, 2006, and period 2 was from April 1, 2006, to March 31, 2008. The rate of positivity was 24.2% during period 1, and 11.6% during period 2 (P<0.001). Repeat CDTT was performed 619 times on samples received on the same day as the initial specimen, and only three (0.5%) were discordant. A total of 1630 samples were retested within one to seven days of a negative result, and 103 (6.3%) tested positive (7.8% period 1 and 2.9% period 2; P=0.002). The likelihood of a positive result on repeat testing in the first three days after a negative result was low (0.9%, 7% and 4%, respectively). The cumulative positivity for repeat testing performed in the first three days was 0.9%, 3.3% and 3.5%, respectively, and did not differ significantly at day 3 during the period of high CDTT positivity (P=0.110).
The value of repeat CDTT, performed using a cell cytotoxicity assay, was low in the first three days after an initial negative result and was unchanged during a CDAD outbreak.
最近艰难梭状芽孢杆菌相关性腹泻（CDAD）的增加导致人们对艰难梭状芽孢杆菌毒素检测（CDTT）的可重复性和敏感性产生了疑问。尽管已经有建议在初次检测为阴性后重复进行 CDTT，但之前的研究未能显示出其益处。然而，在 CDAD 爆发期间并未进行这些研究。本研究报告了在 CDAD 爆发期间和之后接受检测的患者在初次检测为阴性后再次进行 CDTT 的价值，以及在同一天接收和检测多个样本时 CDTT 的可重复性。
检索并搜索了 2001 年 4 月 1 日至 2008 年 3 月 31 日期间使用细胞细胞毒性测定法进行的 CDTT 的结果，并寻找在初次检测为阴性后再次进行重复检测的患者。使用最近一次阴性检测的日期来确定结果和阴性结果后的天数。通过将所考虑天数的所有重复阳性检测结果相加并除以在此期间进行的检测总数来计算累积阳性率。
在研究期间，共有 8661 名患者提交了 14991 份粪便样本进行 CDTT。有 3095 份样本（20.6%）检测出毒素阳性。结果分为两个时间段，以反映 2002 年 4 月开始的 CDAD 爆发：第 1 期（爆发）为 2002 年 4 月 1 日至 2006 年 3 月 31 日，第 2 期为 2006 年 4 月 1 日至 2008 年 3 月 31 日。第 1 期的阳性率为 24.2%，第 2 期为 11.6%（P<0.001）。在同一天收到的初始样本上进行了 619 次重复 CDTT，只有 3 次（0.5%）不一致。共有 1630 份样本在阴性结果后 1 至 7 天内进行了重新检测，其中 103 份（6.3%）呈阳性（第 1 期为 7.8%，第 2 期为 2.9%；P=0.002）。在阴性结果后的头三天内进行重复检测呈阳性的可能性较低（分别为 0.9%、7%和 4%）。在第一个三天内进行重复检测的累积阳性率分别为 0.9%、3.3%和 3.5%，在高 CDTT 阳性率期间的第 3 天差异无统计学意义（P=0.110）。
在初次检测为阴性后的头三天内，使用细胞细胞毒性测定法进行重复 CDTT 的价值较低，并且在 CDAD 爆发期间没有变化。
