Division of Infectious Diseases and HIV Medicine, Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, USA.
Clin Infect Dis. 2013 Aug;57(4):494-500. doi: 10.1093/cid/cit286. Epub 2013 May 3.
Patients with suspected Clostridium difficile infection (CDI) often receive empirical therapy prior to collection of stool specimens for diagnostic testing. The likelihood that such empirical therapy might result in false-negative CDI test results is unknown.
We conducted a prospective study of CDI patients to determine the time to conversion of CDI test results, including polymerase chain reaction (PCR) for toxin B genes, glutamate dehydrogenase, and toxigenic culture, from positive to negative during CDI therapy. We evaluated the frequency of and risk factors for persistence of positive CDI tests. For patients receiving empirical therapy, we assessed the frequency of conversion of positive CDI test results at the time of the test order to negative by the time clinical staff collected stool specimens for testing.
For 51 CDI patients, PCR, glutamate dehydrogenase, and toxigenic culture results converted to negative at similar rates. For PCR, 14%, 35%, and 45% of positive CDI tests converted to negative after 1, 2, and 3 days of treatment, respectively. Increased age and infection with North American pulsed-field gel electrophoresis strains were associated with persistent positive PCR results. For CDI patients diagnosed at the time of the test order, conversion to negative PCR results by the time clinical stool specimens were collected occurred in 4 of 9 (44%) patients who were prescribed empirical CDI therapy versus 0 of 23 (0%) who were not (P = .004).
Empirical treatment for suspected CDI cases may result in false-negative PCR results if there are delays in stool specimen collection.
疑似艰难梭菌感染 (CDI) 的患者在采集粪便标本进行诊断检测前通常会接受经验性治疗。这种经验性治疗可能导致 CDI 检测结果呈假阴性的可能性尚不清楚。
我们对 CDI 患者进行了一项前瞻性研究，以确定 CDI 治疗过程中，毒素 B 基因聚合酶链反应 (PCR)、谷氨酸脱氢酶和产毒培养等 CDI 检测结果从阳性转为阴性的时间。我们评估了 CDI 检测结果持续阳性的频率和风险因素。对于接受经验性治疗的患者，我们评估了从检测开单到临床采集粪便标本进行检测的时间内，阳性 CDI 检测结果转为阴性的频率。
在 51 例 CDI 患者中，PCR、谷氨酸脱氢酶和产毒培养结果的转阴率相似。对于 PCR，14%、35%和 45%的阳性 CDI 检测在治疗 1、2 和 3 天后分别转为阴性。年龄较大和感染北美脉冲场凝胶电泳株与持续阳性 PCR 结果相关。对于在检测开单时诊断为 CDI 的患者，在临床采集粪便标本时转为阴性的 PCR 结果在接受经验性 CDI 治疗的 9 例患者中有 4 例（44%）发生，而未接受治疗的 23 例患者中无 1 例（0%）发生（P =.004）。
如果延迟采集粪便标本，疑似 CDI 病例的经验性治疗可能会导致 PCR 结果呈假阴性。
