Rainbow Babies and Children's Hospital, Cleveland, Ohio, USA.
Infect Control Hosp Epidemiol. 2012 Feb;33(2):175-9. doi: 10.1086/663706. Epub 2011 Dec 20.
To determine the frequency of false-positive Clostridium difficile toxin enzyme immunoassay (EIA) results in hospitalized children and to examine potential reasons for this false positivity.
Nested case-control.
Two tertiary care pediatric hospitals.
As part of a natural history study, prospectively collected EIA-positive stools were cultured for toxigenic C. difficile, and characteristics of children with false-positive and true-positive EIA results were compared. EIA-positive/culture-negative samples were recultured after dilution and enrichment steps, were evaluated for presence of the tcdB gene by polymerase chain reaction (PCR), and were further cultured for Clostridium sordellii, a cause of false-positive EIA toxin assays.
Of 112 EIA-positive stools cultured, 72 grew toxigenic C. difficile and 40 did not, indicating a positive predictive value of 64% in this population. The estimated prevalence of C. difficile infection (CDI) in the study sites among children tested for this pathogen was 5%-7%. Children with false-positive EIA results were significantly younger than those with true-positive tests but did not differ in other characteristics. No false-positive specimens yielded C. difficile when cultured after enrichment or serial dilution, 1 specimen was positive for tcdB by PCR, and none grew C. sordellii.
Approximately one-third of EIA tests used to evaluate pediatric inpatients for CDI were falsely positive. This finding was likely due to the low prevalence of CDI in pediatric hospitals, which diminishes the test's positive predictive value. These data raise concerns about the use of EIA assays to diagnosis CDI in children.
确定住院儿童中假阳性艰难梭菌毒素酶联免疫吸附试验（EIA）结果的频率，并探讨这种假阳性的潜在原因。
巢式病例对照研究。
两家三级儿童保健医院。
作为自然史研究的一部分，前瞻性收集 EIA 阳性粪便进行产毒艰难梭菌培养，并比较 EIA 阳性和真阳性结果的儿童特征。EIA 阳性/培养阴性的样本经过稀释和富集步骤后进行再次培养，通过聚合酶链反应（PCR）评估 tcdB 基因的存在情况，并进一步培养产毒梭状芽孢杆菌，该菌可导致 EIA 毒素检测出现假阳性。
在 112 份培养的 EIA 阳性粪便中，有 72 份培养出产毒艰难梭菌，40 份未培养出产毒艰难梭菌，表明该人群的阳性预测值为 64%。在该病原体检测的研究地点，儿童中艰难梭菌感染（CDI）的估计患病率为 5%-7%。EIA 结果为假阳性的儿童明显比真阳性测试的儿童年龄小，但其他特征无差异。经过富集或连续稀释培养后，没有假阳性标本产生艰难梭菌，1 份标本通过 PCR 检测 tcdB 呈阳性，也没有培养出产毒梭状芽孢杆菌。
用于评估儿科住院患者 CDI 的 EIA 检测中，约有三分之一为假阳性。这一发现可能是由于儿科医院 CDI 的患病率较低，降低了该检测的阳性预测值。这些数据引起了人们对 EIA 检测用于诊断儿童 CDI 的担忧。
