The nose knows not: poor predictive value of stool sample odor for detection of Clostridium difficile.
The nose knows not: poor predictive value of stool sample odor for detection of Clostridium difficile.
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鼻子不知道：粪便样本气味对艰难梭菌检测的预测价值很差。
DOI：
10.1093/cid/cis974
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Newton,DuaneW
中科院分区：
文献类型：
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作者：
Rao,Krishna;Berland,Daniel;Young,Carol;Walk,SethT;Newton,DuaneW
致编辑——艰难梭菌感染 (CDI) 是一种医院感染，通常由于检测延迟而对感染控制程序构成挑战 [1]。护士主导的方案可能会导致更早识别和隔离受感染的患者，从而减少传播。护理人员中常见的“都市传说”是，仅凭粪便气味就能识别 CDI 患者。根据使用气相色谱法的研究，这在生物学上是合理的——2004 年，Probert 等人证明了 CDI 患者的粪便中存在独特的挥发性有机化合物 (VOC) [2]。同样，Garner 等人在 2007 年证明，从 VOC 数据得出的判别评分在区分粪便与无症状、溃疡性结肠炎、空肠弯曲杆菌感染或 CDI 患者方面具有 100% 的预测准确性 [3]。 2002年，Johansen等人发现，病房护士通过粪便气味诊断CDI的敏感性为84%，特异性为77%[4]。同样，2007 年 Burdette 等人发现护士诊断 CDI 的敏感性为 55%，特异性为 83% [5]。正如随附评论中指出的那样 [6]，这两项研究的局限性在于护士并未对患者的任何特征视而不见。因此，人们不能断定粪便气味是他们评估的唯一因素。我们假设护士可以在受控的实验室环境中仅通过气味来检测粪便中艰难梭菌的存在。护士是从我们医院的住院病房招募的。我们的微生物学实验室根据来自液体粪便患者的艰难梭菌毒素 (CDTOX) 两步检测（谷氨酸脱氢酶/毒素酶免疫测定，然后聚合酶链反应，以获得不一致的结果）的结果，随机留出 5 个阳性和 5 个阴性粪便样本。我们向护士询问了他们的工作经验以及他们是否相信自己可以通过气味检测艰难梭菌。他们被要求嗅探每个样本并记录是否存在 CDTOX 阳性粪便。 Fisher 精确检验和 Mann-Whitney 检验用于评估统计显着性。十八名护士参加。经验从 1 年到 30 年不等（其中 8 人拥有超过 10 年的经验）。 11 人对自己的嗅探能力充满信心（61%）。正确率中位数为 45%（范围 40%–80%）。 CDTOX 阳性样本得出的正确答案百分比低于 CDTOX 阴性样本（图 1 A；中位数，31% vs 74%；P=.0119）。没有一个人的表现比偶然更好（平均敏感性/特异性= 0.26/0.69）。那些
TO THE EDITOR—Clostridium difficileinfec-tion (CDI) is a nosocomial infection that poses a challenge to infection control procedures, often from delays in testing [1]. A nurse-driven protocol may result in earlier identification and isolation of infected patients, leading to decreased transmission. It is a common “urban legend” among nursing staff that they can identify patients with CDI by the odor of their stool alone. Based on studies that used gas chromatography, this is biologically plausible—in 2004, Probert et al demonstrated the presence of unique volatile organic compounds (VOCs) in stool from patients with CDI [2]. Similarly, Garner et al demonstrated in 2007 that derived discriminant scores from VOC data had 100% predictive accuracy in distinguishing stool from patients who were asymptomatic, had ulcerative colitis, had Campylobacter jejuni infection, or had CDI [3]. In 2002, Johansen et al found that nurses on the wards were 84% sensitive and 77% specific in diagnosing CDI by stool odor [4]. Similarly, in 2007 Burdette et al found that nurses were 55% sensitive and 83% specific in diagnosing CDI [5]. A limitation of both studies, as pointed out in an accompanying commentary [6], is that the nurses were not blinded to any patient characteristics. Thus, one could not conclude that stool odor was the sole factor informing their assessments. We hypothesized that nurses can detect the presence of C. dif-ficile in stool by odor alone in a controlled, laboratory setting. Nurses were recruited from inpatient wards at our hospital. Our microbiology laboratory randomly set aside 5 positive and 5 negative stool samples based on results from 2-step testing (glutamate dehydrogenase/toxin enzyme immunoassay followed by polymerase chain reaction for discordant results) for C. difficile toxin (CDTOX) from patients with liquid stool. We asked nurses about their work experience and whether they believed they could detect C. difficile by odor. They were instructed to sniff each sample and record whether CDTOX positive stool was present. Fisher exact and Mann-Whitney tests were used to assess statistical significance. Eighteen nurses participated. Experience ranged from 1 to 30 years (8 with> 10 years of experience). Eleven felt confident in their sniffing ability (61%). The median percentage correct was 45%(range, 40%–80%). CDTOX-positive samples elicited a lower percentage of correct answers than CDTOX-negative samples (Figure 1 A; median, 31% vs 74%; P=. 0119). No single individual performed better than chance (mean sensitivity/specificity= 0.26/0.69). Those